@article{doi101016s0021925817308748,
    author = "Chinard, Francis P. and Slyke, Donald D. Van",
    title = "COMPARISON OF A MODIFIED FOLIN PHOTOMETRIC PROCEDURE AND THE NINHYDRIN MANOMETRIC METHOD FOR THE DETERMINATION OF AMINO ACID NITROGEN IN PLASMA",
    year = "1947",
    journal = "Journal of Biological Chemistry",
    abstract = {Evolution of CO2 by reaction of a-amino acids with ninhydrin is characteristic of the groups C(NH2)COOH and C(NH-CR)COOH, and measurement of the evolved CO2 affords the most accurate procedure available for the determination of free a-amino acids in biological material (1). At pH 2, used for application of the procedure to blood filtrates (2), all the amino acids known to be yielded by protein hydrolysis give quantitative yields of CO2 except glycine and tryptophan, which give respect,ively 5 and 10 per cent less than theoretical, and lysine which gives about 5 per cent more ((l), Table The older nitrous acid method (3) and Sgrensen's (4, 5) formaldehyde titration as applied to blood filtrates include aliphatic amines other than amino acids, and proline and hydroxyproline are not determined in the nitrous acid method. The calorimetric procedure developed by Folin (6) likewise includes aliphatic amines other than amino acids (7); however, Van Slyke and Kirk (5) found that when applied to blood and urine the colorimetzic method gave results different from those of t,he formaldehyde titration and the nitrous acid method, which showed approximate agreement with each other. Neither Van Slyke and Kirk (5) nor Re and Potick (8) could obtain by the calorimetric method even approximate recovery of added amino acids. However, a recent photo-metric1 modification of this calorimetric method by Frame, Russell, and Wilhelmi (9) and Russell (lo), which requires but 0.2 ml. of plasma for duplicates, is simple and rapid, and embodies improvements which, it appeared, might make the method sufficiently accurate for many purposes. The work described below was done to determine wit,h what degree of accuracy the photometric procedure, either as described by Frame, Russell, and Wilhehni (9,lO) or with modifications, could be used as a substitute for * Fellow in the Medical Sciences of the National Research Council. 1 The term "photometric" is here used to indicate the procedure in which a pho- tometer measuring optical density is employed, "calorimetric" for one in which a Duboscq type calorimeter is used. The term "photometric nitrogen" describes the nitrogen determined by the photometric procedure, "ninhydrin nitrogen" the nitrogen determined by the ninhydrin-CO:! manometric method. "Ninhydrin nitrogen" is identical with "carboxyl nitrogen" used in some previous publications.},
    url = "https://doi.org/10.1016/s0021-9258(17)30874-8",
    doi = "10.1016/s0021-9258(17)30874-8",
    openalex = "W16996449"
}

@article{doi101085jgp344439,
    author = "Daly, Marie M. and Mirsky, A. E. and Ris, Hans",
    title = "THE AMINO ACID COMPOSITION AND SOME PROPERTIES OF HISTONES",
    year = "1951",
    journal = "The Journal of General Physiology",
    abstract = "Some of the properties and the amino acid compositions of the histones of calf thymus, calf liver, fowl erythrocytes, and of a protamine-like material isolated from rooster sperm were described. The amino acid compositions of the histones were rather similar except that no methionine was found in the fowl erythrocyte histone. In the fowl, histones are found in the somatic chromosomes and protamines are found in the sperm chromosomes. This shows that great variations in chromosome composition can exist in an organism. Histone is digested by pepsin both when isolated and when in the chromosome.",
    url = "https://doi.org/10.1085/jgp.34.4.439",
    doi = "10.1085/jgp.34.4.439",
    openalex = "W2053971733"
}

@article{doi103181003797277819189,
    author = "Stein, William H.",
    title = "Excretion of Amino Acids in Cystinuria",
    year = "1951",
    journal = "Experimental Biology and Medicine",
    abstract = "The amino acid content of the urine of five cystinurics has been determined employing chromatography on columns of the ion exchange resin, Dowex-50. In every case the amount of arginine, lysine, ornithine, and cystine was found to be from 50 to 100 fold the normal level. The quantity of isoleucine was about twice the normal, whereas the taurine output was diminished to about 1/3 or less of normal. All other ninhydrin positive constituents were in the normal range. It is particularly striking that the relative molar excretion of ornithine, cystine, arginine, and lysine, which was found to be about 1:1:2:4, is quite similar from one subject to the next despite the haphazard nature of the case material and the absence of any dietary control. The results suggest the hypothesis that cystinuria involves an enzymatic defect which affects simultaneously at some site or sites (probably the kidney) some phase of the metabolism of arginine, lysine, ornithine, and the sulfur amino acids, and perhaps also isoleucine and taurine.",
    url = "https://doi.org/10.3181/00379727-78-19189",
    doi = "10.3181/00379727-78-19189",
    openalex = "W2329976837"
}

@article{doi101016s0021925818711782,
    author = "Moore, Stanford and Stein, William H.",
    title = "A MODIFIED NINHYDRIN REAGENT FOR THE PHOTOMETRIC DETERMINATION OF AMINO ACIDS AND RELATED COMPOUNDS",
    year = "1954",
    journal = "Journal of Biological Chemistry",
    abstract = "A modified ninhydrin reagent for the photometric determination of amino acids and related compounds, A modified ninhydrin reagent for the photometric determination of amino acids and related compounds, مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی",
    url = "https://doi.org/10.1016/s0021-9258(18)71178-2",
    doi = "10.1016/s0021-9258(18)71178-2",
    openalex = "W1511235377",
    references = "doi101016s0021925818510346, doi101016s0021925818711770"
}

@article{doi101042bj0610589,
    author = "Eastoe, J.E.",
    title = "The amino acid composition of mammalian collagen and gelatin",
    year = "1955",
    journal = "Biochemical Journal",
    abstract = "hyde, but the most serious errors arise when small quantities of amino sugar are estimated in the presence",
    url = "https://doi.org/10.1042/bj0610589",
    doi = "10.1042/bj0610589",
    openalex = "W2344589655",
    references = "doi101016s0021925818711812, doi101016s0021925819777916"
}

@article{doi101021ac60139a006,
    author = "Spackman, D. and Stein, William H. and Moore, Stanford",
    title = "Automatic Recording Apparatus for Use in Chromatography of Amino Acids",
    year = "1958",
    journal = "Analytical Chemistry",
    url = "https://doi.org/10.1021/ac60139a006",
    doi = "10.1021/ac60139a006",
    openalex = "W2017470279",
    references = "doi101016s0021925818510346, doi101016s0021925818649385, doi101016s0021925818704936, doi101016s0021925818711770, doi101016s0021925818711794, doi101016s0021925818711800, doi101016s0021925818711812, doi101016s0021925818713471, doi101016s0021925819777916, doi101021ac60139a005"
}

@article{fox1958thermal,
    author = "Fox, Sidney W. and Harada, Kaoru",
    title = "Thermal Copolymerization of Amino Acids to a Product Resembling Protein",
    year = "1958",
    journal = "Science",
    url = "https://doi.org/10.1126/science.128.3333.1214",
    doi = "10.1126/science.128.3333.1214",
    number = "3333",
    pages = "1214-1214",
    volume = "128"
}

@misc{fox1958thermal3,
    author = "Fox, S. W. and Harada, K",
    title = "Thermal copolymerization of amino acids to a product resembling protein",
    year = "1958",
    howpublished = "Science, v. 128, p. 1214",
    note = "talkorigins\_source = {true}; raw\_reference = {Fox, S. W., and Harada, K., 1958, Thermal copolymerization of amino acids to a product resembling protein: Science, v. 128, p. 1214.}"
}

@article{doi101007bf02301336,
    author = "Fox, Sidney W. and Harada, Kaoru and Vegotsky, Allen",
    title = "Thermal polymerization of amino acids and a theory of biochemical origins",
    year = "1959",
    journal = "Cellular and Molecular Life Sciences",
    url = "https://doi.org/10.1007/bf02301336",
    doi = "10.1007/bf02301336",
    openalex = "W2035600603",
    references = "doi101007bf02160390, doi1010160006300253901413, doi101016s0065323308605033, doi101021ja01544a027, doi101021ja01639a083, doi101039jr9560001444, doi101111j174966321936tb56976x, doi101111j174966321957tb49669x, doi101126science1243228923, doi105059yukigoseikyokaishi141"
}

@article{doi1010160003986160904185,
    author = "Harada, Kaoru and Fox, Sidney W.",
    title = "The thermal copolymerization of aspartic acid and glutamic acid",
    year = "1960",
    journal = "Archives of Biochemistry and Biophysics",
    url = "https://doi.org/10.1016/0003-9861(60)90418-5",
    doi = "10.1016/0003-9861(60)90418-5",
    openalex = "W2000538650",
    references = "doi101007bf00584166, doi101007bf00646968, doi101007bf02165821, doi101016s0065323308605033, doi101021ed034p472, doi101021ja01544a027, doi101021ja01546a042, doi101039jr9560001444, doi105059yukigoseikyokaishi141, fox1958thermal"
}

@article{doi101021ja01499a069,
    author = "Fox, Sidney W. and Harada, Kaoru",
    title = "The Thermal Copolymerization of Amino Acids Common to Protein 1",
    year = "1960",
    journal = "Journal of the American Chemical Society",
    url = "https://doi.org/10.1021/ja01499a069",
    doi = "10.1021/ja01499a069",
    openalex = "W2318108904"
}

@article{doi101093oxfordjournalsjbchema127083,
    author = "Okuyama, Tsuneo and Satake, Kazuo",
    title = "ON THE PREPARATION AND PROPERTIES OF 2,4,6-TRINITROPHENYL-AMINO ACIDS AND -PEPTIDES*",
    year = "1960",
    journal = "The Journal of Biochemistry",
    abstract = "Journal Article ON THE PREPARATION AND PROPERTIES OF 2,4,6-TRINITROPHENYL-AMINO ACIDS AND -PEPTIDES Get access TSUNEO OKUYAMA, TSUNEO OKUYAMA Faculty of Science From the Department of Chemistry, Tokyo Metropolitan UniversityTokyo Search for other works by this author on: Oxford Academic PubMed Google Scholar KAZUO SATAKE KAZUO SATAKE Faculty of Science From the Department of Chemistry, Tokyo Metropolitan UniversityTokyo Search for other works by this author on: Oxford Academic PubMed Google Scholar The Journal of Biochemistry, Volume 47, Issue 4, 25 April 1960, Pages 454–466, https://doi.org/10.1093/oxfordjournals.jbchem.a127083 Published: 25 April 1960 Article history Received: 30 September 1959 Published: 25 April 1960",
    url = "https://doi.org/10.1093/oxfordjournals.jbchem.a127083",
    doi = "10.1093/oxfordjournals.jbchem.a127083",
    openalex = "W1877845887"
}

@article{doi101093oxfordjournalsjbchema127107,
    author = "Satake, Kazuo and Okuyama, Tsuneo and Ohashi, Mochihiko and Shinoda, Tomotaka",
    title = "THE SPECTROPHOTOMETRIC DETERMINATION OF AMINE, AMINO ACID AND PEPTIDE WITH 2,4,6- TRINITROBENZENE 1-SULFONIC ACID*",
    year = "1960",
    journal = "The Journal of Biochemistry",
    abstract = "Journal Article THE SPECTROPHOTOMETRIC DETERMINATION OF AMINE, AMINO ACID AND PEPTIDE WITH 2,4,6- TRINITROBENZENE 1-SULFONIC ACID Get access KAZUO SATAKE, KAZUO SATAKE Faculty of Science From the Department of Chemistry, Tokyo Metropolitan UniversityTokyo Search for other works by this author on: Oxford Academic PubMed Google Scholar TSUNEO OKUYAMA, TSUNEO OKUYAMA Faculty of Science From the Department of Chemistry, Tokyo Metropolitan UniversityTokyo Search for other works by this author on: Oxford Academic PubMed Google Scholar MOCHIHIKO OHASHI, MOCHIHIKO OHASHI Faculty of Science From the Department of Chemistry, Tokyo Metropolitan UniversityTokyo Search for other works by this author on: Oxford Academic PubMed Google Scholar TOMOTAKA SHINODA TOMOTAKA SHINODA Faculty of Science From the Department of Chemistry, Tokyo Metropolitan UniversityTokyo Search for other works by this author on: Oxford Academic PubMed Google Scholar The Journal of Biochemistry, Volume 47, Issue 5, 25 May 1960, Pages 654–660, https://doi.org/10.1093/oxfordjournals.jbchem.a127107 Published: 25 May 1960 Article history Received: 16 November 1959 Published: 25 May 1960",
    url = "https://doi.org/10.1093/oxfordjournals.jbchem.a127107",
    doi = "10.1093/oxfordjournals.jbchem.a127107",
    openalex = "W1772093770"
}

@article{fox1960thermal,
    author = "Fox, Sidney W. and Harada, Kaoru",
    title = "Thermal copolymerization of amino acids in the presence of phosphoric acid",
    year = "1960",
    journal = "Archives of Biochemistry and Biophysics",
    url = "https://doi.org/10.1016/0003-9861(60)90419-7",
    doi = "10.1016/0003-9861(60)90419-7",
    number = "2",
    pages = "281-285",
    volume = "86"
}

@book{fox1962the5,
    author = "Fox, S. W. and Harada, K. and Rohlfing, D. L",
    title = "The thermal copolymerization of -amino acids, in Stahmann, M. A., ed., Polyamino Acids, Polypeptides, and Proteins",
    year = "1962",
    publisher = "Madison, Wisconsin, University of Wisconsin Press, p. 47-54",
    note = "talkorigins\_source = {true}; raw\_reference = {Fox, S. W., Harada, K., and Rohlfing, D. L., 1962, The thermal copolymerization of -amino acids, in Stahmann, M. A., ed., Polyamino Acids, Polypeptides, and Proteins: Madison, Wisconsin, University of Wisconsin Press, p. 47-54.}"
}

@article{fox1963effects8,
    author = "Fox, S. W. and Yuyama, S",
    title = "Effects of the Gram stain on microspheres from thermal polyamino acids",
    year = "1963",
    journal = "Journal of Bacteriology, v. 85, p. 279-283",
    note = "talkorigins\_source = {true}; raw\_reference = {Fox, S. W., and Yuyama, S., 1963, Effects of the Gram stain on microspheres from thermal polyamino acids: Journal of Bacteriology, v. 85, p. 279-283.}"
}

@misc{fox1964thermal1,
    author = "Fox, S. W",
    title = "Thermal polymerization of amino acids and production of formed microparticles on lava",
    year = "1964",
    howpublished = "Nature, v. 201, p. 336-337",
    note = "talkorigins\_source = {true}; raw\_reference = {Fox, S. W., 1964, Thermal polymerization of amino acids and production of formed microparticles on lava: Nature, v. 201, p. 336-337.}"
}

@book{harada1965thermal10,
    author = "Harada, K. and Fox, S. W",
    title = "Thermal polycondensation of free amino acids with polyphosphatic acid, in Fox, S. W., ed., The Origins of Prebiological Systems",
    year = "1965",
    publisher = "New York, Academic Press, p. 289-308",
    note = "talkorigins\_source = {true}; raw\_reference = {Harada, K., and Fox, S. W., 1965, Thermal polycondensation of free amino acids with polyphosphatic acid, in Fox, S. W., ed., The Origins of Prebiological Systems: New York, Academic Press, p. 289-308.}"
}

@misc{fox1966simulation6,
    author = "Fox, S. W. and Joseph, D. and McCauley, R. J. and Windsor, C. R. and Yuyama, S",
    title = "Simulation of organismic morphology and behavior by synthetic poly--amino acids, in Brown, A. H., and Florkin, M., eds., Life Sciences and Space Research",
    year = "1966",
    howpublished = "Washington, D.C., Spartan Books, v. IV, p. 111-120",
    note = "talkorigins\_source = {true}; raw\_reference = {Fox, S. W., Joseph, D., McCauley, R. J., Windsor, C. R., and Yuyama, S., 1966, Simulation of organismic morphology and behavior by synthetic poly--amino acids, in Brown, A. H., and Florkin, M., eds., Life Sciences and Space Research: Washington, D.C., Spartan Books, v. IV, p. 111-120.}"
}

@misc{hayakawa1967copolymerization11,
    author = "Hayakawa, T. and Windsor, C. R. and Fox, S. W",
    title = "Copolymerization of the Leuchs anhydrides of the eighteen amino acids common to protein",
    year = "1967",
    howpublished = "Archives of Biochemistry and Biophysiology, v. 118, p. 265-272",
    note = "talkorigins\_source = {true}; raw\_reference = {Hayakawa, T., Windsor, C. R., and Fox, S. W., 1967, Copolymerization of the Leuchs anhydrides of the eighteen amino acids common to protein: Archives of Biochemistry and Biophysiology, v. 118, p. 265-272.}"
}

@misc{rohlfing1967the19,
    author = "Rohlfing, D. L",
    title = "The catalytic decarboxylation of oxaloacetic acid by thermally prepared poly--aminoacids",
    year = "1967",
    howpublished = "Archives of Biochemistry and Biophysiology, v. 118, p. 468-474",
    note = "talkorigins\_source = {true}; raw\_reference = {Rohlfing, D. L., 1967, The catalytic decarboxylation of oxaloacetic acid by thermally prepared poly--aminoacids: Archives of Biochemistry and Biophysiology, v. 118, p. 468-474.}"
}

@misc{rohlfing1967the21,
    author = "Rohlfing, D. L. and Fox, S. W",
    title = "The catalytic activity of thermal polyanhydro--amino acids for the hydrolysis of p-nitrophenyl acetate",
    year = "1967",
    howpublished = "Archives of Biochemistry and Biophysiology, v. 118, p. 127-132",
    note = "talkorigins\_source = {true}; raw\_reference = {Rohlfing, D. L., and Fox, S. W., 1967, The catalytic activity of thermal polyanhydro--amino acids for the hydrolysis of p-nitrophenyl acetate: Archives of Biochemistry and Biophysiology, v. 118, p. 127-132.}"
}

@misc{rohlfing1967thermal18,
    author = "Rohlfing, D. L",
    title = "Thermal poly--amino acids containing low proportions of aspartic acid",
    year = "1967",
    howpublished = "Nature, v. 216, p. 657-659",
    note = "talkorigins\_source = {true}; raw\_reference = {Rohlfing, D. L., 1967, Thermal poly--amino acids containing low proportions of aspartic acid: Nature, v. 216, p. 657-659.}"
}

@misc{usdin1967inhibition23,
    author = "Usdin, V. R. and Mitz, M. A. and Killos, P. J",
    title = "Inhibition and reactivation of the catalytic activity of a thermal -amino acid copolymer",
    year = "1967",
    howpublished = "Archives of Biochemistry and Biophysiology, v. 122, p. 258-261",
    note = "talkorigins\_source = {true}; raw\_reference = {Usdin, V. R., Mitz, M. A., and Killos, P. J., 1967, Inhibition and reactivation of the catalytic activity of a thermal -amino acid copolymer: Archives of Biochemistry and Biophysiology, v. 122, p. 258-261.}"
}

@article{doi101016s0021925818944881,
    author = "Moore, Shannon J.",
    title = "Amino Acid Analysis: Aqueous Dimethyl Sulfoxide As Solvent for the Ninhydrin Reaction",
    year = "1968",
    journal = "Journal of Biological Chemistry",
    abstract = "Abstract Methyl Cellosolve (the monomethyl ether of ethylene glycol) has been widely used as the organic solvent in ninhydrin reagents for amino acid analysis; it has, however, properties that are disadvantageous in a reagent for everyday employment. The solvent is toxic and it is difficult to keep the ether peroxide-free. A continuing effort to arrive at a chemically preferable and relatively nontoxic substitute for methyl Cellosolve has led to experiments with dimethyl sulfoxide, which proves to be a better solvent for the reduced form of ninhydrin (hydrindantin) than is methyl Cellosolve. Dimethyl sulfoxide can replace the latter, volume for volume, in a ninhydrin reagent mixture that gives equal performance and has improved stability. The result is a ninhydrin-hydrindantin solution in 75\% dimethyl sulfoxide-25\% 4 m lithium acetate buffer at pH 5.2. This type of mixture, with appropriate hydrindantin concentrations, is recommended to replace methyl Cellosolve-containing reagents in the quantitative determination of amino acids by automatic analyzers and by the manual ninhydrin method.",
    url = "https://doi.org/10.1016/s0021-9258(18)94488-1",
    doi = "10.1016/s0021-9258(18)94488-1",
    openalex = "W1501912047",
    references = "doi101016s0021925818510346, doi101021ac60139a005"
}

@misc{fox1968melanocytestimulating7,
    author = "Fox, S. W. and Wang, C.-T",
    title = "Melanocyte-stimulating hormone activity on thermal properties of -amino acids",
    year = "1968",
    howpublished = "Science, v. 160, p. 547-548",
    note = "talkorigins\_source = {true}; raw\_reference = {Fox, S. W., and Wang, C.-T., 1968, Melanocyte-stimulating hormone activity on thermal properties of -amino acids: Science, v. 160, p. 547-548.}"
}

@misc{oshima1968the17,
    author = "Oshima, T",
    title = "The catalytic hydrolysis of phosphate ester bonds by thermal polymers of amino acids",
    year = "1968",
    howpublished = "Archives of Biochemistry and Biophysiology, v. 126, p. 478-485",
    note = "talkorigins\_source = {true}; raw\_reference = {Oshima, T., 1968, The catalytic hydrolysis of phosphate ester bonds by thermal polymers of amino acids: Archives of Biochemistry and Biophysiology, v. 126, p. 478-485.}"
}

@article{doi101073pnas622399,
    author = "Krampitz, Gottfried and Fox, Sidney W.",
    title = "THE CONDENSATION OF THE ADENYLATES OF THE AMINO ACIDS COMMON TO PROTEIN",
    year = "1969",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "Simultaneous formation of the adenylates of the 18 amino acids common to protein, followed by cocondensation, has yielded polymers containing all of those amino acids. The condensation occurred rapidly at room temperature above pH 7. The activated amino acids were reacted with thermally synthesized polyanhydro-alpha-amino acids to yield polymers of substantially increased size. The modified polyamino acids form micron-sized particles which demonstrate internal synthesis by growth and budding. These particles are stable over a wide range of pH. From thermal polyamino acids alone, answers have earlier been obtained, in principle, to questions of the primordial origin of enzymes, cellular structure, membranes, systematic anhydroamino acid sequences, and propagation of microsystems. Such a model is largely heterotrophic; the mixed adenylate condensation provides, in principle, a partial answer to the origin of syntheses of peptide bonds within protocellular structures.",
    url = "https://doi.org/10.1073/pnas.62.2.399",
    doi = "10.1073/pnas.62.2.399",
    openalex = "W2081308094",
    references = "doi101007bf02301336"
}

@article{doi101111j143210331969tb19632x,
    author = "Gros, Claude P. and Labouesse, Bernard",
    title = "Study of the Dansylation Reaction of Amino Acids, Peptides and Proteins",
    year = "1969",
    journal = "European Journal of Biochemistry",
    abstract = "The reaction rates between dansyl chloride and water, amino acids or peptides are studied as a function of pH and temperature. The rate of hydrolysis of dansyl chloride is constant and low up to pH 9.5 and above this pH it increases rapidly. The various reactive groups of amino acids and peptides react with dansyl chloride in their unprotonated form. It is shown that a compromise for optima conditions of dansylation (pH and temperature) may be found, taking into account the rate of hydrolysis and the pK of the group to be dansylated. A complete chromatographic separation on Silica gel G thin layer plates of dansyl amino acids is proposed using 4 solvents. The quantitative recovery of the separated derivatives is described. The study of the acid hydrolysis of dansylated proteins shows that the release of the dansyl derivatives from the peptide chain is faster than that of free amino acids; it also shows that the destruction of dansyl amino acids occurs rather rapidly. Therefore a hydrolysis time of 4 hours (110°) is suggested, except in the special cases of the release of dansyl valine, dansyl leucine or dansyl isoleucine which needs 18 hours of hydrolysis. For quantitative estimation of each dansyl derivative a correction factor is given, taking into account the loss during hydrolysis, the recovery from the plates and the individual fluorescence of any dansyl derivative as compared to the fluorescence of a reference compound. The general conditions described in this work require 1 nmole of material for qualitative determination of the N‐terminal amino acids, and 5–10 nmoles for their quantitative estimation. Some examples (α‐chymotrypsin, trypsinogen, ribonuclease, lysozyme, aspartokinase and triose phosphate dehydrogenase) illustrate the efficiency of the method.",
    url = "https://doi.org/10.1111/j.1432-1033.1969.tb19632.x",
    doi = "10.1111/j.1432-1033.1969.tb19632.x",
    openalex = "W1987484067"
}

@article{doi101172jci106017,
    author = "Felig, Philip and Owen, Oliver E. and Wahren, John and Cahill, George F.",
    title = "Amino acid metabolism during prolonged starvation",
    year = "1969",
    journal = "Journal of Clinical Investigation",
    abstract = "Plasma concentration, splanchnic and renal exchange, and urinary excretion of 20 amino acids were studied in obese subjects during prolonged (5-6 wk) starvation. Splanchnic amino acid uptake was also investigated in postabsorptive and briefly (36-48 hr) fasted subjects.A transient increase in plasma valine, leucine, isoleucine, methionine, and alpha-aminobutyrate was noted during the 1st wk of starvation. A delayed, progressive increase in glycine, threonine, and serine occurred after the 1st 5 days. 13 of the amino acids ultimately decreased in starvation, but the magnitude of this diminution was greatest for alanine which decreased most rapidly during the 1st week of fasting. In all subjects alanine was extracted by the splanchnic circulation to a greater extent than all other amino acids combined. Brief fasting resulted in an increased arterio-hepatic venous difference for alanine due to increased fractional extraction. After 5-6 wk of starvation, a marked falloff in splanchnic alanine uptake was attributable to the decreased arterial concentration. Prolonged fasting resulted in increased glycine utilization by the kidney and in net renal uptake of alanine. It is concluded that the marked decrease in plasma alanine is due to augmented and preferential splanchnic utilization of this amino acid in early starvation resulting in substrate depletion. Maintenance of the hypoalaninemia ultimately serves to diminish splanchnic uptake of this key glycogenic amino acid and is thus an important component of the regulatory mechanism whereby hepatic gluconeogenesis is diminished and protein catabolism is minimized in prolonged fasting. The altered renal extraction of glycine and alanine is not due to increased urinary excretion but may be secondary to the increased rate of renal gluconeogenesis observed in prolonged starvation.",
    url = "https://doi.org/10.1172/jci106017",
    doi = "10.1172/jci106017",
    openalex = "W2119975151",
    references = "doi101016s0021925818711794, doi101016s0021925818713471"
}

@incollection{rohlfing1969catalytic,
    author = "Rohlfing, Duane L. and Fox, Sidney W.",
    title = "Catalytic Activities of Thermal Polyanhydro-α-Amino Acids",
    year = "1969",
    booktitle = "Advances in Catalysis",
    url = "https://doi.org/10.1016/s0360-0564(08)60277-1",
    doi = "10.1016/s0360-0564(08)60277-1",
    openalex = "W1555925392",
    pages = "373-418",
    references = "doi1010160003986163902522, doi101016s0065323308606087, doi101021cr60203a005, doi101021ja00973a068, doi101021ja01030a050, doi101021ja01499a069, doi101021ja01544a027, doi1010382031362a0, doi1023072420646, doi105962bhltitle4528"
}

@misc{rohlfing1969catalytic22,
    author = "Rohlfing, D. L. and Fox, S. W",
    title = "Catalytic activities of thermal polyanhydro--amino acids",
    year = "1969",
    howpublished = "Advances in Catalysis, v. 20, p. 373-418",
    note = "talkorigins\_source = {true}; raw\_reference = {Rohlfing, D. L., and Fox, S. W., 1969, Catalytic activities of thermal polyanhydro--amino acids: Advances in Catalysis, v. 20, p. 373-418.}"
}

@article{berlin1970synthesis,
    author = "Berlin, A.A. and Liogon'kii, B.I. and Shamrayev, G.M.",
    title = "Synthesis and studies of some polyamino amino acids",
    year = "1970",
    journal = "Polymer Science U.S.S.R.",
    url = "https://doi.org/10.1016/0032-3950(70)90405-3",
    doi = "10.1016/0032-3950(70)90405-3",
    number = "4",
    pages = "1067-1077",
    volume = "12"
}

@incollection{doi101007978146842019718,
    author = "Rohlfing, Duane L. and Fouche, Clarence E.",
    title = "Stereo-Enriched Poly-α-Amino Acids: Synthesis Under Postulated Prebiotic Conditions",
    year = "1972",
    url = "https://doi.org/10.1007/978-1-4684-2019-7\_18",
    doi = "10.1007/978-1-4684-2019-7\_18",
    openalex = "W1493183103",
    references = "doi1010079783662126417, doi101007bf00599584, doi1010160003986169900563, doi101016s0021925818711782, doi101021ja01499a069, doi101038205328a0, doi1010970000044119640100000017, doi1010970001069419690400000017, doi10120197814200703475, lemmon1970chemical"
}

@article{doi101111j143210331973tb03026x,
    author = "Goodwin, Graham H. and Sanders, Clive and Johns, Ernest W.",
    title = "A New Group of Chromatin‐Associated Proteins with a High Content of Acidic and Basic Amino Acids",
    year = "1973",
    journal = "European Journal of Biochemistry",
    abstract = "A new group of chromatin‐associated proteins having a high content of acidic and basic amino acids have been isolated from the 0.35 M NaCl‐extractable proteins from calf thymus. This new group, designated “high‐mobility group” proteins have been partially separated and some interesting new proteins identified. One such protein contains over 55\% acidic and basic amino acids.",
    url = "https://doi.org/10.1111/j.1432-1033.1973.tb03026.x",
    doi = "10.1111/j.1432-1033.1973.tb03026.x",
    openalex = "W1985009522",
    references = "doi101021ac60139a005"
}

@incollection{doi101007978940151118619,
    author = "Dose, Klaus",
    title = "Chemical and Catalytical Properties of Thermal Polymers of Amino Acids (Proteinoids)",
    year = "1974",
    url = "https://doi.org/10.1007/978-94-015-1118-6\_19",
    doi = "10.1007/978-94-015-1118-6\_19",
    openalex = "W4248178677",
    references = "doi101007978146842019718"
}

@article{doi101007bf00927028,
    author = "Dose, Klaus",
    title = "Chemical and catalytical properties of thermal polymers of amino acids (proteinoids)",
    year = "1974",
    journal = "Origins of Life and Evolution of Biospheres",
    url = "https://doi.org/10.1007/bf00927028",
    doi = "10.1007/bf00927028",
    openalex = "W2056519029",
    references = "doi101007978146842019718"
}

@article{doi101016s0021925819420139,
    author = "Fulks, Richard M. and Li, J B and Goldberg, Alfred L.",
    title = "Effects of insulin, glucose, and amino acids on protein turnover in rat diaphragm.",
    year = "1975",
    journal = "Journal of Biological Chemistry",
    abstract = "A simple method is described for measuring rates of protein synthesis and degradation in isolated rat diaphragm. Muscles incubated in Krebs-Ringer bicarbonate buffer showed a linear rate of synthesis for 3 hours. At the same time, the muscle released tyrosine and ninhydrin-positive material, primarily amino acids, at a linear rate. This release was not a nonspecific leakage of material from the intracellular pools, but reflected net protein degradation. Tyrosine was chosen for studies of protein turnover, since it rapidly equilibrates between intracellular pools and the medium, it can be measured fluorometrically, and it is neither synthesized nor degraded by this tissue. To follow protein degradation independently of synthesis, muscles were incubated in the presence of cycloheximide. Under these conditions, the amount of tyrosine in the intracellular pools was constant, while the muscle released tyrosine at a linear rate. This tyrosine release was used as a measure of degradation. This preparation was used to study the influence of various factors known to be important for muscle growth on protein synthesis and degradation. Similar effects were obtained with diaphragms of normal and fasted rats although the latter showed decreased synthesis and increased protein degradation. Insulin by itself not only stimulated synthesis but also inhibited protein degradation (even in the presence of cycloheximide). These two effects served to reduce the net release of tyrosine from muscle protein to comparable extents. Effects of insulin on synthesis and degradation were greater when glucose was also present in the medium. Glucose by itself inhibited protein degradation but in the absence of insulin glucose had no significant effect on synthesis. Nevertheless, glucose stimulated incorporation of radioactivive tyrosine into protein, but this effect was due to an increased intracellular specific activity. Unlike glucose neither beta-hydroxybutyrate or octanoic acid had any demonstrable effects on protein degradion. The addition of amino acids at plasma concentrations both promoted protein synthesis and inhibited degradation in the diaphragm. Five times normal plasma concentrations of the amino acids had larger effects. The three branched chain amino acids together stimulated synthesis and reduced degradation, while the remaining plasma amino acids did not affect either process significantly. Thus leucine, isoleucine, and valine appear responsible for the effects of plasma amino or isoleucine and valine together, also were able to inhibit protein degradation and promote synthesis.",
    url = "https://doi.org/10.1016/s0021-9258(19)42013-9",
    doi = "10.1016/s0021-9258(19)42013-9",
    openalex = "W1491317952",
    references = "doi101016s0021925818510346"
}

@phdthesis{hennen1975the13,
    author = "Hennen, G. and Plaquet, R. and Biserte, G",
    title = "The synthesis of amino acid polymers by thermal condensation at 105° without a catalyst",
    year = "1975",
    publisher = "Biochimie, v. 57, p. 1395-1396",
    note = "talkorigins\_source = {true}; raw\_reference = {Hennen, G., Plaquet, R., and Biserte, G., 1975, The synthesis of amino acid polymers by thermal condensation at 105° without a catalyst: Biochimie, v. 57, p. 1395-1396.}"
}

@misc{melius1975thermal14,
    author = "Melius, P. and Sheng, Y. Y.-P",
    title = "Thermal condensation of a mixture of six amino acids",
    year = "1975",
    howpublished = "Bioorganic Chemistry, v. 4, p. 385-391",
    note = "talkorigins\_source = {true}; raw\_reference = {Melius, P., and Sheng, Y. Y.-P., 1975, Thermal condensation of a mixture of six amino acids: Bioorganic Chemistry, v. 4, p. 385-391.}"
}

@article{doi1010160303264776900095,
    author = "Fouche, Clarence E. and Rohlfing, Duane L.",
    title = "Thermal polymerization of amino acids under various atmospheres or at low pressures",
    year = "1976",
    journal = "Biosystems",
    url = "https://doi.org/10.1016/0303-2647(76)90009-5",
    doi = "10.1016/0303-2647(76)90009-5",
    openalex = "W2050928133",
    references = "doi101007978146842019718"
}

@article{doi1010160303264776900162,
    author = "Rohlfing, Duane L. and McAlhaney, Walter W.",
    title = "The thermal polymerization of amino acids in the presence of sand",
    year = "1976",
    journal = "Biosystems",
    url = "https://doi.org/10.1016/0303-2647(76)90016-2",
    doi = "10.1016/0303-2647(76)90016-2",
    openalex = "W2003831880",
    references = "doi101007978146842019718"
}

@article{doi101016s0021925817336372,
    author = "Simpson, Robert J. and Neuberger, M R and Liu, T Y",
    title = "Complete amino acid analysis of proteins from a single hydrolysate.",
    year = "1976",
    journal = "Journal of Biological Chemistry",
    abstract = "An analytical procedure which affords the precise amino acid composition of a protein or a peptide from a single hydrolysate is described. This method utilizes 4 N methanesulfonic acid containing 0.2\% 3-(2-aminoethyl)indole, rather then 6N HCl as a catalyst for hydrolysis. The hydrolysis is carried out in vacuo (20 mu) at 115 degrees for 22 to 72 hours. Half-cystine is determined as S-sulfocysteine by treating the hydrolysate with dithiothreitol followed by an excess of tetrathionate. The values of all amino acids, including tryptophan and half-cystine, were close to the expected theoretical values for the proteins examined. The method has the advantage that the neutralized hydrolysate can be applied directly to an ion exchange column. Further, the method is capable of distinguishing between free sulfhydryl groups as S-carbosymethylcysteine and disulfides as S-sulfocysteine. A limitation of the procedure is that tryptophan remains sensitive to the presence of carbohydrate in the sample.",
    url = "https://doi.org/10.1016/s0021-9258(17)33637-2",
    doi = "10.1016/s0021-9258(17)33637-2",
    openalex = "W1574128379"
}

@phdthesis{rohlfing1976thermal20,
    author = "Rohlfing, D. L",
    title = "Thermal polyamino acids",
    year = "1976",
    publisher = "synthesis at less than 100° C: Science, v. 193, p. 68-70",
    note = "talkorigins\_source = {true}; raw\_reference = {Rohlfing, D. L., 1976, Thermal polyamino acids: synthesis at less than 100° C: Science, v. 193, p. 68-70.}"
}

@article{nakashima1977a16,
    author = "Nakashima, T. and Jungck, J. R. and Fox, S. W. and Lederer, E. and Das, B. C",
    title = "A test for randomness in peptides isolated from a thermal polyamino acid",
    year = "1977",
    journal = "International Journal of Quantum Chemistry, v. QBS4, p. 65-72",
    note = "talkorigins\_source = {true}; raw\_reference = {Nakashima, T., Jungck, J. R., Fox, S. W., Lederer, E., and Das, B. C., 1977, A test for randomness in peptides isolated from a thermal polyamino acid: International Journal of Quantum Chemistry, v. QBS4, p. 65-72.}"
}

@misc{grote1978effect9,
    author = "Grote, J. R. and Syren, R. M. and Fox, S. W",
    title = "Effect of product from heated amino acids on conductance in lipid bilayer membrenes and nonaqueous solvents",
    year = "1978",
    howpublished = "BioSystems, v. 10, p. 287-292",
    note = "talkorigins\_source = {true}; raw\_reference = {Grote, J. R., Syren, R. M., and Fox, S. W., 1978, Effect of product from heated amino acids on conductance in lipid bilayer membrenes and nonaqueous solvents: BioSystems, v. 10, p. 287-292.}"
}

@article{doi1010160303264779900194,
    author = "Harada, Kaoru and Matsuyama, Masayo",
    title = "Polycondensation of thermal precursors of amino acids and characterization of constituent amino acids",
    year = "1979",
    journal = "Biosystems",
    url = "https://doi.org/10.1016/0303-2647(79)90019-4",
    doi = "10.1016/0303-2647(79)90019-4",
    openalex = "W2021291270",
    references = "doi101007bf02165821"
}

@article{fox1980response2,
    author = "Fox, S. W",
    title = "Response to repeated statements on temperatures required for polycondensation of amino acids",
    year = "1980",
    journal = "Journal of Molecular Evolution, v. 15, p. 539",
    note = "talkorigins\_source = {true}; raw\_reference = {Fox, S. W., 1980, Response to repeated statements on temperatures required for polycondensation of amino acids: Journal of Molecular Evolution, v. 15, p. 539.}"
}

@phdthesis{nakashima1980synthesis15,
    author = "Nakashima, T. and Fox, S. W",
    title = "Synthesis of peptides from amino acids and ATP with lysine-rich protenoid",
    year = "1980",
    publisher = "Journal of Molecular Evolution, v. 15, p. 161-168",
    note = "talkorigins\_source = {true}; raw\_reference = {Nakashima, T., and Fox, S. W., 1980, Synthesis of peptides from amino acids and ATP with lysine-rich protenoid: Journal of Molecular Evolution, v. 15, p. 161-168.}"
}

@article{doi1010160303264781900551,
    author = "Hartmann, Jürgen and Brand, M. Christel and Dose, Klaus",
    title = "Formation of specific amino acid sequences during thermal polymerization of amino acids",
    year = "1981",
    journal = "Biosystems",
    url = "https://doi.org/10.1016/0303-2647(81)90055-1",
    doi = "10.1016/0303-2647(81)90055-1",
    openalex = "W2054632312",
    references = "doi101007978146842019718"
}

@article{doi10108001483918108059956,
    author = "Jones, Barry and Pääbo, Svante and Stein, Stanley J.",
    title = "Amino Acid Analysis and Enzymatic Sequence Determination of Peptides by an Improved o -Phthaldialdehyde Precolumn Labeling Procedure",
    year = "1981",
    journal = "Journal of Liquid Chromatography",
    abstract = "Abstract Primary amino acids react with o-phthaldialdehyde in the presence of mercaptans to form intensely fluorescent derivatives. By the use of reverse-phase high-performance liquid chromatography, a mixture containing 26 of these derivatives was efficiently resolved with an analysis time of less than 35 minutes. The quantitation of the individual amino acids was reproducible with an average relative deviation of ± 1.4\% and had a detection limit of approximately 50 femtomoles. Improvements in the stability and fluorescence response of lysine and hydroxylysine were obtained by the incorporation of sodium dodecyl sulfate in the derivatizing medium. Applications of the chromatography system involving the amino acid analysis of peptides after either acid or enzymatic hydrolysis are presented. Methods for the sequence analysis of picomole quantities of peptides by time course hydrolysis with exopeptidases were also developed, which employed the above separation procedure for the identification and quantification of the released amino acids.",
    url = "https://doi.org/10.1080/01483918108059956",
    doi = "10.1080/01483918108059956",
    openalex = "W2023822557",
    references = "doi101021ac50047a019"
}

@misc{fox1981amino4,
    author = "Fox, S. W. and Harada, K. and Hare, P. E",
    title = "Amino acids from the Moon",
    year = "1981",
    howpublished = "Notes on meteorites: Subcellular Biochemistry, v. 8, p. 357-373",
    note = "talkorigins\_source = {true}; raw\_reference = {Fox, S. W., Harada, K., and Hare, P. E., 1981, Amino acids from the Moon: Notes on meteorites: Subcellular Biochemistry, v. 8, p. 357-373.}"
}

@misc{heinz1981the12,
    author = "Heinz, B. and Ried, W",
    title = "The formation of chromophores through amino acids thermolysis and their possible role as prebiotic photoreceptors",
    year = "1981",
    howpublished = "BioSystems, v. 14, p. 33-40",
    note = "talkorigins\_source = {true}; raw\_reference = {Heinz, B., and Ried, W., 1981, The formation of chromophores through amino acids thermolysis and their possible role as prebiotic photoreceptors: BioSystems, v. 14, p. 33-40.}"
}

@article{doi1010161044030594800162,
    author = "Eng, Jimmy K. and McCormack, Ashley L. and Yates, John R.",
    title = "An approach to correlate tandem mass spectral data of peptides with amino acid sequences in a protein database",
    year = "1994",
    journal = "Journal of the American Society for Mass Spectrometry",
    abstract = "A method to correlate the uninterpreted tandem mass spectra of peptides produced under low energy (10-50 eV) collision conditions with amino acid sequences in the Genpept database has been developed. In this method the protein database is searched to identify linear amino acid sequences within a mass tolerance of ±1 u of the precursor ion molecular weight A cross-correlation function is then used to provide a measurement of similarity between the mass-to-charge ratios for the fragment ions predicted from amino acid sequences obtained from the database and the fragment ions observed in the tandem mass spectrum. In general, a difference greater than 0.1 between the normalized cross-correlation functions of the first- and second-ranked search results indicates a successful match between sequence and spectrum. Searches of species-specific protein databases with tandem mass spectra acquired from peptides obtained from the enzymatically digested total proteins of E. coli and S. cerevisiae cells allowed matching of the spectra to amino acid sequences within proteins of these organisms. The approach described in this manuscript provides a convenient method to interpret tandem mass spectra with known sequences in a protein database.",
    url = "https://doi.org/10.1016/1044-0305(94)80016-2",
    doi = "10.1016/1044-0305(94)80016-2",
    openalex = "W2026465178",
    references = "doi101126science2675315, openalexw2282054059"
}

@article{doi1023071940891,
    author = "Kielland, Knut",
    title = "Amino Acid Absorption by Arctic Plants: Implications for Plant Nutrition and Nitrogen Cycling",
    year = "1994",
    journal = "Ecology",
    abstract = "Recent studies of nitrogen (N) cycling in arctic tundra have indicated that inorganic N supplied to plants by mineralization is not sufficient to meet the annual requirement of N by many tundra species. Whereas N mineralization is slow in tundra soils and concentrations of inorganic N are low, these soils have large stocks of both structural and soluble organic N. In light of these observations, kinetics of absorption of three amino acids (glycine, aspartic acid, and glutamic acid) were measured in dominant vascular plant species of the four major ecosystems types in arctic Alaska and compared with concentrations of free amino acids in soils. Absorption rates were measured on roots using 1 4 C—labeled substrates. Concentrations of free amino acids in soil were measured on water—extracted samples by high pressure liquid chromatography. All species had higher capacity (V m a x) for ammonium uptake (measured using methylamine as an ammonium analogue) than for any amino acid. However, at concentrations observed in the field, uptake rates estimated for amino acids were similar to (glycine) or less than (aspartic and glutamic acids) that for ammonium. On the basis of these comparisons, uptake rates of the three amino acids together may account for between 10 and 82\% of the total N uptake in the field, depending on species and community. Deciduous shrubs had higher uptake rates than the more slowly growing evergreen shrubs, suggesting that new growth created a sink that strongly influenced capacity for amino acid uptake. In general, ectomycorrhizal species had higher amino acid uptake than did non—mycorrhizal species. In species that were sampled from more than one community, amino acid uptake rates were highest in the community where a given amino acid was most abundant in the soil. The results indicate that, in arctic tundra, plants short—circuit the mineralization step of decomposition by directly absorbing amino acids. This implies that in the organic soils of these tundra systems (1) inorganic nitrogen is an inadequate measure of plant—available soil nitrogen, (2) mineralization rates underestimate nitrogen supply rates to plants, (3) the large differences among species in capacities to absorb different forms of N provide ample basis for niche differentiation of what was previously considered a single resource, and (4) by short—circuiting N mineralization, plants accelerate N turnover and effectively exert greater control over N cycling than has been previously recognized.",
    url = "https://doi.org/10.2307/1940891",
    doi = "10.2307/1940891",
    openalex = "W2069065722",
    references = "doi101021ac50047a019, openalexw1558206756"
}

@article{doi101126science2815377670,
    author = "Huber, Claudia and Wächtershäuser, Günter",
    title = "Peptides by Activation of Amino Acids with CO on (Ni,Fe)S Surfaces: Implications for the Origin of Life",
    year = "1998",
    journal = "Science",
    abstract = "In experiments modeling volcanic or hydrothermal settings amino acids were converted into their peptides by use of coprecipitated (Ni,Fe)S and CO in conjunction with H2S (or CH3SH) as a catalyst and condensation agent at 100 degreesC and pH 7 to 10 under anaerobic, aqueous conditions. These results demonstrate that amino acids can be activated under geochemically relevant conditions. They support a thermophilic origin of life and an early appearance of peptides in the evolution of a primordial metabolism.",
    url = "https://doi.org/10.1126/science.281.5377.670",
    doi = "10.1126/science.281.5377.670",
    openalex = "W2166068250",
    references = "doi101016s0047248478800529"
}

@article{doi101021ac990976y,
    author = "Soga, Tomoyoshi and Heiger, David N.",
    title = "Amino Acid Analysis by Capillary Electrophoresis Electrospray Ionization Mass Spectrometry",
    year = "2000",
    journal = "Analytical Chemistry",
    abstract = "A method for the determination of underivatized amino acids based on capillary electrophoresis coupled to electrospray ionization mass spectrometry (CE-ESI-MS) is described. To analyze free amino acids simultaneously a low acidic pH condition was used to confer positive charge on whole amino acids. The choice of the electrolyte and its concentration influenced resolution and peak shape of the amino acids, and 1 M formic acid was selected as the optimal electrolyte. Meanwhile, the sheath liquid composition had a significant effect on sensitivity and the highest sensitivity was obtained when 5 mM ammonium acetate in 50\% (v/v) methanol-water was used. Protonated amino acids were roughly separated by CE and selectively detected by a quadrupole mass spectrometer with a sheath flow electrospray ionization interface. Under the optimized conditions, 19 free amino acids normally found in proteins and several physiological amino acids were well determined in less than 17 min. The detection limits for basic amino acids were between 0.3 and 1.1 mumol/L and for acidic and low molecular weight amino acids were less than 6.0 mumol/L with pressure injection of 50 mbar for 3 s (3 nL) at a signal-to-noise ratio of 3. This method is simple, rapid, and selective compared with conventional techniques and could be readily applied to the analysis of free amino acids in soy sauce.",
    url = "https://doi.org/10.1021/ac990976y",
    doi = "10.1021/ac990976y",
    openalex = "W1995888001",
    references = "doi1010160003269784903075, doi101016s0021925819777916"
}

@article{doi101074mcpm200025mcp200,
    author = "Ong, Shao‐En and Blagoev, Blagoy and Kratchmarova, Irina and Kristensen, Dan Bach and Steen, Hanno and Pandey, Akhilesh and Mann, Matthias",
    title = "Stable Isotope Labeling by Amino Acids in Cell Culture, SILAC, as a Simple and Accurate Approach to Expression Proteomics",
    year = "2002",
    journal = "Molecular \& Cellular Proteomics",
    abstract = "Quantitative proteomics has traditionally been performed by two-dimensional gel electrophoresis, but recently, mass spectrometric methods based on stable isotope quantitation have shown great promise for the simultaneous and automated identification and quantitation of complex protein mixtures. Here we describe a method, termed SILAC, for stable isotope labeling by amino acids in cell culture, for the in vivo incorporation of specific amino acids into all mammalian proteins. Mammalian cell lines are grown in media lacking a standard essential amino acid but supplemented with a non-radioactive, isotopically labeled form of that amino acid, in this case deuterated leucine (Leu-d3). We find that growth of cells maintained in these media is no different from growth in normal media as evidenced by cell morphology, doubling time, and ability to differentiate. Complete incorporation of Leu-d3 occurred after five doublings in the cell lines and proteins studied. Protein populations from experimental and control samples are mixed directly after harvesting, and mass spectrometric identification is straightforward as every leucine-containing peptide incorporates either all normal leucine or all Leu-d3. We have applied this technique to the relative quantitation of changes in protein expression during the process of muscle cell differentiation. Proteins that were found to be up-regulated during this process include glyceraldehyde-3-phosphate dehydrogenase, fibronectin, and pyruvate kinase M2. SILAC is a simple, inexpensive, and accurate procedure that can be used as a quantitative proteomic approach in any cell culture system.",
    url = "https://doi.org/10.1074/mcp.m200025-mcp200",
    doi = "10.1074/mcp.m200025-mcp200",
    openalex = "W2140946052",
    references = "doi101002sici15222683200004012161037aidelps103730co2v, doi101016s0021925819414968, doi101021ac00096a002, doi101021ac950914h, doi10103813690, doi101038379466a0, doi10103886783, doi101038nbt1001946, doi101073pnas96126591, doi101083jcb1423873"
}

@article{doi101021ie020733n,
    author = "Sato, Nobuaki and Quitain, Armando T. and Kang, Kilyoon and Daimon, Hiroyuki and Fujie, Koichi",
    title = "Reaction Kinetics of Amino Acid Decomposition in High-Temperature and High-Pressure Water",
    year = "2004",
    journal = "Industrial \& Engineering Chemistry Research",
    abstract = "Decomposition behavior of five selected amino acids in high-temperature and high-pressure water was studied using a continuous-flow tubular reactor. The reaction was carried out in the temperature range of 200−340 °C at a pressure of 20 MPa. Alanine and its derivatives leucine, phenylalanine, serine, and aspartic acid were used as model amino acids. The effect of temperature on reaction products, pathway, and rate was determined as a function of reaction time. Alanine decomposed into lactic acid and pyruvic acid, then finally mineralized to carbon dioxide with an activation energy of 154 [kJ/mol] at 20 MPa. The degradation rate decreased in the following order: aspartic acid, serine, phenylalanine, leucine, and alanine. The general reaction network of amino acids under hydrothermal conditions takes two main paths: deamination to produce ammonia and organic acids, and decarboxylation to produce carbonic acid and amines. Deamination was the predominant reaction in the decomposition of aspartic acid, an acidic amino acid. Production of glycine and alanine from serine, an oxy amino acid, was also observed.",
    url = "https://doi.org/10.1021/ie020733n",
    doi = "10.1021/ie020733n",
    openalex = "W2003949804"
}

@incollection{bhushan2008amino,
    author = "Bhushan, Ravi",
    title = "Amino Acids",
    year = "2008",
    booktitle = "Chromatographic Science Series",
    url = "https://doi.org/10.1201/9781420046786.ch13",
    doi = "10.1201/9781420046786.ch13",
    openalex = "W4214921230"
}

@article{doi101073pnas1019191108,
    author = "Parker, Eric T. and Cleaves, Henderson James and Dworkin, Jason P. and Glavin, D. P. and Callahan, Michael P. and Aubrey, A. D. and Lazcano, Antonio and Bada, Jeffrey L.",
    title = "Primordial synthesis of amines and amino acids in a 1958 Miller H 2 S-rich spark discharge experiment",
    year = "2011",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "Archived samples from a previously unreported 1958 Stanley Miller electric discharge experiment containing hydrogen sulfide (H(2)S) were recently discovered and analyzed using high-performance liquid chromatography and time-of-flight mass spectrometry. We report here the detection and quantification of primary amine-containing compounds in the original sample residues, which were produced via spark discharge using a gaseous mixture of H(2)S, CH(4), NH(3), and CO(2). A total of 23 amino acids and 4 amines, including 7 organosulfur compounds, were detected in these samples. The major amino acids with chiral centers are racemic within the accuracy of the measurements, indicating that they are not contaminants introduced during sample storage. This experiment marks the first synthesis of sulfur amino acids from spark discharge experiments designed to imitate primordial environments. The relative yield of some amino acids, in particular the isomers of aminobutyric acid, are the highest ever found in a spark discharge experiment. The simulated primordial conditions used by Miller may serve as a model for early volcanic plume chemistry and provide insight to the possible roles such plumes may have played in abiotic organic synthesis. Additionally, the overall abundances of the synthesized amino acids in the presence of H(2)S are very similar to the abundances found in some carbonaceous meteorites, suggesting that H(2)S may have played an important role in prebiotic reactions in early solar system environments.",
    url = "https://doi.org/10.1073/pnas.1019191108",
    doi = "10.1073/pnas.1019191108",
    openalex = "W2135893268",
    references = "doi101126science1161527"
}

@article{doi101039c3cs60345h,
    author = "Lundberg, Helena and Tinnis, Fredrik and Selander, Nicklas and Adolfsson, Hans",
    title = "Catalytic amide formation from non-activated carboxylic acids and amines",
    year = "2014",
    journal = "Chemical Society Reviews",
    abstract = "The amide functionality is found in a wide variety of biological and synthetic structures such as proteins, polymers, pesticides and pharmaceuticals. Due to the fact that synthetic amides are still mainly produced by the aid of coupling reagents with poor atom-economy, the direct catalytic formation of amides from carboxylic acids and amines has become a field of emerging importance. A general, efficient and selective catalytic method for this transformation would meet well with the increasing demands for green chemistry procedures. This review covers catalytic and synthetically relevant methods for direct condensation of carboxylic acids and amines. A comprehensive overview of homogeneous and heterogeneous catalytic methods is presented, covering biocatalysts, Lewis acid catalysts based on boron and metals as well an assortment of other types of catalysts.",
    url = "https://doi.org/10.1039/c3cs60345h",
    doi = "10.1039/c3cs60345h",
    openalex = "W2092526937",
    references = "doi101016jprogpolymsci200705010"
}

@article{doi101007s1114401509727,
    author = "Maciejowska, Anna and Godziek, Agnieszka and Sajewicz, Mieczysław and Kowalska, Teresa",
    title = "Investigation of spontaneous non-linear peptidization dynamics and mechanism with selected α-amino acid pairs",
    year = "2015",
    journal = "Reaction Kinetics Mechanisms and Catalysis",
    abstract = "The goal of this study was to provide experimental evidence on the dynamics and mechanism of spontaneous oscillatory peptidization in an abiotic system with three α-amino acid pairs (L-Met-L-Ser, L-His-L-Thr, and L-Cys-L-Phg), and to discuss these data in the context of an earlier established theoretical model. For each individual α-amino acid in a monocomponent and binary system, the dynamics of peptidization was traced with aid of the high performance liquid chromatograph with the evaporative light scattering detector. As an auxiliary technique, mass spectrometry (MS) was employed to scrutinize structures of the resulting peptides. With L-Met-L-Ser and L-His-L-Thr, the dynamics of one amino acid (L-Met and L-Thr, respectively) dominated over that of its counterpart. With L-Cys-L-Phg, no such predominance of the dynamics of one α-amino acid over that of its counterpart was observed. Mass spectrometric results confirmed the formation of heteropeptides with each investigated α-amino acid pair. With L-Met-L-Ser, L-His-L-Thr, and L-Cys-L-Phg, synchronization of the oscillatory behavior in the binary systems was observed, witnessing to mutual cross-catalysis of the two counterparts, assumed by case 4 of the theoretical model.",
    url = "https://doi.org/10.1007/s11144-015-0972-7",
    doi = "10.1007/s11144-015-0972-7",
    openalex = "W2303754601",
    references = "doi101556jpc282015210"
}

@article{liu2016catalytic,
    author = "Liu, Guangyi and Wright, Mark M. and Zhao, Qingliang and Brown, Robert C. and Wang, Kaige and Xue, Yuan",
    title = "Catalytic pyrolysis of amino acids: Comparison of aliphatic amino acid and cyclic amino acid",
    year = "2016",
    journal = "Energy Conversion and Management",
    url = "https://doi.org/10.1016/j.enconman.2016.01.024",
    doi = "10.1016/j.enconman.2016.01.024",
    openalex = "W2286125981",
    pages = "220-225",
    volume = "112",
    references = "doi101016jbiombioe200909012, doi101016jbiortech201411050, doi101016jenconman200903001, doi101016jjaap200311004, doi101016jjcat200912013, doi101016jwatres200607030, doi101021ef0502397, doi101039c1ee01230d, doi101039c3gc41288a, doi10108001614949208020306"
}

@article{doi101007s111440171221z,
    author = "Godziek, Agnieszka and Łągiewka, Anna and Kowalska, Teresa and Sajewicz, Mieczysław",
    title = "The influence of heavy water as a solvent on the spontaneous oscillatory reactions of α-amino acids",
    year = "2017",
    journal = "Reaction Kinetics Mechanisms and Catalysis",
    abstract = "In our earlier investigations, we have discovered that α-amino acids dissolved in water or aqueous-organic solvents undergo spontaneous oscillatory chiral inversion and oscillatory peptidization in parallel, and the dynamics of these processes strongly depends on the chemical structure of a given amino acid, physicochemical characteristics of a solvent used, ambient temperature, etc. The aim of this study was to perform a preliminary reconnaissance on the possible impact of D2O on the dynamics of spontaneous behavior of the selected test α-amino acids (L-Phe, L-His, L-Pro and L-Cys) stored at 25 ± 0.5 °C for the period of 1 week. As the measuring techniques, turbidimetry in continuous registration mode and mass spectrometry were employed. For the sake of comparison, the analogous results were presented for the discussed α-amino acids dissolved in the aqueous organic solvents and originally published elsewhere. Based on a comparison of the turbidimetric fingerprints, the dynamics of the turbidity changes in heavy water have proved rather moderate. Mass spectrometric results provided a confirmatory evidence witnessing to rather negligible peptide yields in heavy water. Thus, turbidimetric and mass spectrometric data have served as complementary proofs of a considerable hampering of spontaneous peptidization of α-amino acids in D2O.",
    url = "https://doi.org/10.1007/s11144-017-1221-z",
    doi = "10.1007/s11144-017-1221-z",
    openalex = "W2734465939",
    references = "doi101556jpc282015210"
}

@article{doi101021acssuschemeng6b03140,
    author = "Verduyckt, Jasper and Coeck, Robin and Vos, Dirk De",
    title = "Ru-Catalyzed Hydrogenation–Decarbonylation of Amino Acids to Bio-based Primary Amines",
    year = "2017",
    journal = "ACS Sustainable Chemistry \& Engineering",
    abstract = "Amino acids are considered to be a valuable renewable resource for the production of bio-based chemicals. Here, the Ru-catalyzed hydrogenation–decarbonylation toward primary amines is presented. In contrast to the direct Pd-catalyzed decarboxylation, this catalytic system operates at much lower temperatures, safeguarding the stability of the primary amines. Moreover, instead of producing CO2, the cleaved carbon is released as CH4, which can be recycled for other applications (e.g., energy purposes). After a general catalyst screening, the Ru-based system is optimized for the model reaction of l-valine in water, resulting in isobutylamine yields of up to 87\%. Stronger acidity in the aqueous solution improves the stability of isobutylamine, but simultaneously promotes the parallel formation of 2-amino-3-methylbutane, which is the most important side product. This tradeoff is controlled by adding an appropriate amount of H3PO4. Besides pH, the other reaction parameters are also screened: H2 pressure, temperature, and catalyst-to-substrate ratio. Kinetic profiles are recorded to gain a thorough understanding of the reaction network and the product stability. Finally, the stability and broad applicability of the Ru/C catalyst are demonstrated.",
    url = "https://doi.org/10.1021/acssuschemeng.6b03140",
    doi = "10.1021/acssuschemeng.6b03140",
    openalex = "W2591150531",
    references = "doi101016jgca2006061558"
}

@article{doi101021acsearthspacechem0c00183,
    author = "Bedoin, Lise and Alvès, Sandra and Lambert, Jean‐François",
    title = "Origins of Life and Molecular Information: Selectivity in Mineral Surface-Induced Prebiotic Amino Acid Polymerization",
    year = "2020",
    journal = "ACS Earth and Space Chemistry",
    abstract = "In current living matter, biopolymers follow specific sequences that give them special properties, such as the sequence of amino acids (AAs) in proteins and peptides. A major challenge for the elucidation of the origins of life lies in understanding how, for example, nonrandom polypeptides have been selected among all the possible ones. While many investigations established plausible prebiotic polymerization pathways, surprisingly, only a few attempted to study the selectivity of these processes. We studied a mineral surface polymerization scenario based on moderate thermal activation of leucine + glutamic acid mixtures on silica. Oligopeptides up to octamers were quantitatively formed in a “clean” prebiotic reaction and analyzed by high-resolution mass spectrometry and Fourier transform ion cyclotron resonance spectrometry for unambiguous molecular assignments. Nontrivial oligomerization selectivities are evidenced in both stoichiometric compositions and AA sequences, while comparable selectivities are not observed in other polymerization scenarios. This must therefore be due to specific catalytic reaction pathways occurring on the SiO2 surface. A statistical measure of information contained in oligopeptide distributions is proposed. It could be used to follow the evolution of potentially meaningful complexity in biopolymers from the mineral to the biochemical world.",
    url = "https://doi.org/10.1021/acsearthspacechem.0c00183",
    doi = "10.1021/acsearthspacechem.0c00183",
    openalex = "W3087299006",
    references = "doi101002anie201503792, doi101002bies10192, doi101002bms1200111109, doi101002j153873051948tb01338x, doi101002mas10008, doi101002sici1098278719981711aidmas130co2k, doi101007s1108400891283, doi101073pnas1019191108, doi101126science1173046528, doi101126science663639, fox1960thermal"
}

@article{doi103390sym12122046,
    author = "Zaia, Dimas Augusto Morozin and Zaia, Cássia Thaïs Bussamra Vieira",
    title = "A Few Experimental Suggestions Using Minerals to Obtain Peptides with a High Concentration of L-Amino Acids and Protein Amino Acids",
    year = "2020",
    journal = "Symmetry",
    abstract = "The peptides/proteins of all living beings on our planet are mostly made up of 19 L-amino acids and glycine, an achiral amino acid. Arising from endogenous and exogenous sources, the seas of the prebiotic Earth could have contained a huge diversity of biomolecules (including amino acids), and precursors of biomolecules. Thus, how were these amino acids selected from the huge number of available amino acids and other molecules? What were the peptides of prebiotic Earth made up of? How were these peptides synthesized? Minerals have been considered for this task, since they can preconcentrate amino acids from dilute solutions, catalyze their polymerization, and even make the chiral selection of them. However, until now, this problem has only been studied in compartmentalized experiments. There are separate experiments showing that minerals preconcentrate amino acids by adsorption or catalyze their polymerization, or separate L-amino acids from D-amino acids. Based on the [GADV]-protein world hypothesis, as well as the relative abundance of amino acids on prebiotic Earth obtained by Zaia, several experiments are suggested. The main goal of these experiments is to show that using minerals it is possible, at least, to obtain peptides whose composition includes a high quantity of L-amino acids and protein amino acids (PAAs). These experiments should be performed using hydrothermal environments and wet/dry cycles. In addition, for hydrothermal environment experiments, it is very important to use one of the suggested artificial seawaters, and for wet/dry environments, it is important to perform the experiments in distilled water and diluted salt solutions. Finally, from these experiments, we suggest that, without an RNA world or even a pre genetic world, a small peptide set could emerge that better resembles modern proteins.",
    url = "https://doi.org/10.3390/sym12122046",
    doi = "10.3390/sym12122046",
    openalex = "W3111091408",
    references = "doi101021acsearthspacechem0c00183"
}

@article{doi101002marc202100615,
    author = "Leiske, Meike N. and Kempe, Kristian",
    title = "A Guideline for the Synthesis of Amino‐Acid‐Functionalized Monomers and Their Polymerizations",
    year = "2021",
    journal = "Macromolecular Rapid Communications",
    abstract = "Amino acids have emerged as a sustainable source for the design of functional polymers. Besides their wide availability, especially their high degree of biocompatibility makes them appealing for a broad range of applications in the biomedical research field. In addition to these favorable characteristics, the versatility of reactive functional groups in amino acids (i.e., carboxylic acids, amines, thiols, and hydroxyl groups) makes them suitable starting materials for various polymerization approaches, which include step- and chain-growth reactions. This review aims to provide an overview of strategies to incorporate amino acids into polymers. To this end, it focuses on the preparation of polymerizable monomers from amino acids, which yield main chain or side chain-functionalized polymers. Furthermore, postpolymerization modification approaches for polymer side chain functionalization are discussed. Amino acids are presented as a versatile platform for the development of polymers with tailored properties.",
    url = "https://doi.org/10.1002/marc.202100615",
    doi = "10.1002/marc.202100615",
    openalex = "W3213271036",
    references = "doi103390nano11051119"
}

@article{doi103390nano11051119,
    author = "Thompson, Marisa and Scholz, Carmen",
    title = "Highly Branched Polymers Based on Poly(amino acid)s for Biomedical Application",
    year = "2021",
    journal = "Nanomaterials",
    abstract = "Polymers consisting of amino acid building blocks continue to receive consideration for biomedical applications. Since poly(amino acid)s are built from natural amino acids, the same building blocks proteins are made of, they are biocompatible, biodegradable and their degradation products are metabolizable. Some amino acids display a unique asymmetrical AB2 structure, which facilitates their ability to form branched structures. This review compares the three forms of highly branched polymeric structures: structurally highly organized dendrimers, dendrigrafts and the less organized, but readily synthesizable hyperbranched polymers. Their syntheses are reviewed and compared, methods of synthesis modulations are considered and variations on their traditional syntheses are shown. The potential use of highly branched polymers in the realm of biomedical applications is discussed, specifically their applications as delivery vehicles for genes and drugs and their use as antiviral compounds. Of the twenty essential amino acids, L-lysine, L-glutamic acid, and L-aspartic acid are asymmetrical AB2 molecules, but the bulk of the research into highly branched poly(amino acid)s has focused on the polycationic poly(L-lysine) with a lesser extent on poly(L-glutamic acid). Hence, the majority of potential applications lies in delivery systems for nucleic acids and this review examines and compares how these three types of highly branched polymers function as non-viral gene delivery vectors. When considering drug delivery systems, the small size of these highly branched polymers is advantageous for the delivery of inhalable drug. Even though highly branched polymers, in particular dendrimers, have been studied for more than 40 years for the delivery of genes and drugs, they have not translated in large scale into the clinic except for promising antiviral applications that have been commercialized.",
    url = "https://doi.org/10.3390/nano11051119",
    doi = "10.3390/nano11051119",
    openalex = "W3157707026",
    references = "doi101016jbiomaterials201803046, doi101016jprogpolymsci200705010, doi101021ar200094a, doi101021bc015525a, doi101021ja00167a094, doi101021ja01856a062, doi101021ma971197r, doi101021mp050023q, doi101146annurevmatsci062910100429, fox1958thermal"
}

@article{doi101002cplu202300642,
    author = "Samrout, Ola El and Berlier, Gloria and Lambert, Jean‐François",
    title = "Amino Acid Polymerization on Silica Surfaces",
    year = "2024",
    journal = "ChemPlusChem",
    abstract = "The polymerization of unactivated amino acids (AAs) is an important topic because of its applications in various fields including industrial medicinal chemistry and prebiotic chemistry. Silica as a promoter for this reaction, is of great interest owing to its large abundance and low cost. The amide/peptide bond synthesis on silica has been largely demonstrated but suffers from a lack of knowledge regarding its reaction mechanism, the key parameters, and surface features that influence AA adsorption and reactivity, the selectivity of the reaction product, the role of water in the reaction, etc. The present review addresses these problems by summarizing experimental and modeling results from the literature and attempts to rationalize some apparent divergences in published results. After briefly presenting the main types of silica surface sites and other relevant macroscopic features, we discuss the different deposition procedures of AAs, whose importance is often neglected. We address the possible AA adsorption mechanisms including covalent grafting and H-bonding and show that they are highly dependent on silanol types and density. We then consider how the adsorption mechanisms determine the occurrence and outcome of AA condensation (formation of cyclic dimers or of long linear chains), and outline some recent results that suggest significant polymerization selectivity in systems containing several AAs, as well as the formation of specific elements of secondary structure in the growing polypeptide chains.",
    url = "https://doi.org/10.1002/cplu.202300642",
    doi = "10.1002/cplu.202300642",
    openalex = "W4390919132",
    references = "doi101021acsearthspacechem0c00183"
}

@article{doi101016jgca202402020,
    author = "Millman, Emily and Chatterjee, Anamika and Parker, Kimberly M. and Catalano, Jeffrey G.",
    title = "Cation exchange to montmorillonite induces selective adsorption of amino acids",
    year = "2024",
    journal = "Geochimica et Cosmochimica Acta",
    abstract = "Concentrating simple organic molecules, such as amino acids, in the adsorbed phase could have been an early step in prebiotic evolution towards more complex bio-macromolecules on the early Earth. Smectite clay minerals represent potential selective sorbents for prebiotic molecules because of their negative structural charge and high surface area. This study evaluated the adsorption behavior of amino acids to montmorillonite, a well-characterized smectite, at varying pH and fluid compositions. At both pH 5 and 7 in a sodium chloride fluid, amino acids with basic sidechains (L-arginine and L-lysine), which are primarily cationic under these conditions, were selectively adsorbed to montmorillonite with Langmuir constants much greater than amino acids that were predominantly zwitterionic or anionic in solution. On average, the Langmuir constants for the cationic amino acids were 30 (pH 5) and 50 (pH 7) times greater than the constants for zwitterionic amino acids and 120 (pH 5) and 80 (pH 7) times greater than the constants for L-glutamic acid. Under the same pH conditions in a magnesium chloride solution, the adsorption of L-arginine and L-lysine was substantially inhibited with Langmuir constants ∼ 10 times smaller. These observations suggest that cation exchange is the dominant adsorption mechanism for amino acids on montmorillonite. X-ray diffraction and infrared spectroscopy indicate that L-arginine and L-lysine enter the smectite interlayer where the protonated amino sidechain has the strongest interactions with the mineral surface, further supporting adsorption driven primarily through electrostatic interactions. Therefore, smectites on the early Earth may have selectively concentrated cationic amino acids, providing a potential template for the polymerization of α-amine linked peptides.",
    url = "https://doi.org/10.1016/j.gca.2024.02.020",
    doi = "10.1016/j.gca.2024.02.020",
    openalex = "W4392373186",
    references = "doi101021acsearthspacechem0c00183"
}

@article{doi101021acsmacromol4c00614,
    author = "Carboni, Davide and Cadeddu, M and Stagi, Luigi and Anedda, Roberto and Menduti, Luigi and Cola, Luisa De and Malfatti, Luca and Innocenzi, Plinio",
    title = "Structural Insights into Low-Temperature Copolymerization of Thermodegradable Amino Acids Mediated by Pyroglutamic Acid",
    year = "2024",
    journal = "Macromolecules",
    abstract = "The demand for biocompatible multifunctional systems for bioimaging is driving the interest in new-generation fluorescent peptide based on nonaromatic amino acids such as l-glutamic acid and l-alanine. In general, due to the high melting points characterizing the zwitterionic structures of amino acids, their thermal polymerization is performed at temperatures between 200 and 300 °C. However, in this range of temperatures, most of the amino acids tend to decompose rather than undergo polymerization. The present work shows how to obtain nonaromatic fluorescent peptides at temperatures as low as 160 °C by copolymerizing l-glutamic acid with other high-melting amino acids, such as l-alanine, l-valine, and l-leucine. The low-temperature conversion of l-glutamic acid into pyroglutamic acid and its copolymerization with another amino acid were fully characterized by infrared and NMR spectroscopies, MS spectrometry, and thermal analysis. The reaction is mediated by the in situ transformation of l-glutamic acid into pyroglutamic acid, which acts simultaneously as an inomer, initiator + monomer, as well as a dispersing agent, allowing copolymerization with another amino acid. The resulting peptides exhibit fluorescent emission in the visible range typical of PGA derivatives, but they also possess a different polar nature that is inherited by the side chain of the second amino acid.",
    url = "https://doi.org/10.1021/acs.macromol.4c00614",
    doi = "10.1021/acs.macromol.4c00614",
    openalex = "W4401903566",
    references = "doi1010160003986160904185"
}

@article{doi101038s42004024012646,
    author = "Šponer, Judit E. and Coulon, Rémi and Otyepka, Michal and Šponer, Jiřı́ and Siegle, Alexander F. and Trapp, Oliver and Ślepokura, Katarzyna and Zdráhal, Zbyněk and Šedo, Ondřej",
    title = "Phosphoric acid salts of amino acids as a source of oligopeptides on the early Earth",
    year = "2024",
    journal = "Communications Chemistry",
    abstract = "Because of their unique proton-conductivity, chains of phosphoric acid molecules are excellent proton-transfer catalysts. Here we demonstrate that this property could have been exploited for the prebiotic synthesis of the first oligopeptide sequences on our planet. Our results suggest that drying highly diluted solutions containing amino acids (like glycine, histidine and arginine) and phosphates in comparable concentrations at elevated temperatures (ca. 80 °C) in an acidic environment could lead to the accumulation of amino acid:phosphoric acid crystalline salts. Subsequent heating of these materials at 100 °C for 1-3 days results in the formation of oligoglycines consisting of up to 24 monomeric units, while arginine and histidine form shorter oligomers (up to trimers) only. Overall, our results suggest that combining the catalytic effect of phosphate chains with the crystalline order present in amino acid:phosphoric acid salts represents a viable solution that could be utilized to generate the first oligopeptide sequences in a mild acidic hydrothermal field scenario. Further, we propose that crystallization could help overcoming cyclic oligomer formation that is a generally known bottleneck of prebiotic polymerization processes preventing further chain growth.",
    url = "https://doi.org/10.1038/s42004-024-01264-6",
    doi = "10.1038/s42004-024-01264-6",
    openalex = "W4401814404",
    references = "doi101002anie201503792, doi101007bf02165821, doi1010160022024887902314, doi101017s0885715614000840, doi101021acschemrev9b00664, doi101021cr5001496, doi101021ja01544a027, doi101038nchem1329, doi101089ast20192045, doi101107s2052520616003954, doi101126science1102722, fox1958thermal, fox1960thermal"
}

@article{doi101039d4nr04481a,
    author = "Yuan, Huilin and Jiang, Mingxia and Fang, Huapan and Tian, Huayu",
    title = "Recent advances in poly(amino acids), polypeptides, and their derivatives in drug delivery",
    year = "2024",
    journal = "Nanoscale",
    abstract = "Poly(amino acids), polypeptides, and their derivatives have demonstrated significant potential as biodegradable biomaterials in the field of drug delivery. As degradable drug carriers, they can effectively load or conjugate drug molecules including small molecule drugs, nucleic acids, peptides, and protein-based drugs, enhancing the stability and targeting of the drugs in vivo. This strategy ultimately facilitates precise drug delivery and controlled release, thereby improving therapeutic efficacy and reducing side effects within the body. This review systematically describes the structural characteristics and preparation methods of poly(amino acids) and polypeptides, summarizes the advantages of poly(amino acids), polypeptides, and their derivatives in drug delivery, and detailedly introduces the latest advancements in this area. The review also discusses current challenges and opportunities associated with poly(amino acids), peptides, and their derivatives, and offers insights into the future directions for these biodegradable materials. This review aims to provide valuable references for scientific research and clinical translation of biodegradable biomaterials based on poly(amino acids) and peptides.",
    url = "https://doi.org/10.1039/d4nr04481a",
    doi = "10.1039/d4nr04481a",
    openalex = "W4405478575",
    references = "doi103390nano11051119, doi103390pharmaceutics15112641"
}

@article{doi101021acsoprd5c00433,
    author = "Mohammadi, Milad and Swist, Nicole and Rasmussen, Jon H. and Pawlas, Jan",
    title = "Ene and Epoxide Impurities in Fluorenylmethoxycarbonyl (Fmoc) α-Substituted Amino Acids: Causes of Formation, Reactivity, and Means of Minimization",
    year = "2026",
    journal = "Organic Process Research \& Development",
    abstract = "Carpino’s invention of fluorenylmethoxycarbonyl (Fmoc) as a base-labile amino protecting group (PG) (J. Am. Chem. Soc. 1970, 92, 5748) has transformed peptide chemistry in a manner so profound that only Merrifield’s solid-phase peptide synthesis (J. Am. Chem. Soc. 1963, 85, 2149) does not pale in its comparison. In fact, Fmoc is the most important PG in peptide chemistry with no viable alternatives in sight, enabling the assembly of a staggering variety of peptides including blockbuster therapeutics. Here, we report that α-Fmoc amino acids (Fmoc-AA-OHs) are susceptible to undergo formation of impurities differing from parent compounds by −2 and +14 Da, respectively. Based on tandem mass spectrometry (MSMS) analyses, we propose that these byproducts are ene and epoxide alterations of the Fmoc group, situated adjacent to the fluorene core of Fmoc. The generality of these Fmoc-ene/-epoxide byproducts was exemplified by detecting them in five Fmoc-AA-OHs by liquid chromatography high-resolution mass spectrometry (LC-HRMS), while based on the dependence of the rate of Fmoc-ene/-epoxide formation on temperature, air, and iron, we propose storage and handling protocols aimed at keeping the content of ene/epoxide Fmoc alterations to a minimum. Finally, we report that Fmoc-ene/-epoxide alterations are stable toward the coupling additive ethyl cyanohydroxyiminoacetate (Oxyma) and the Fmoc removal base piperidine, whereas exposure to the standard cleavage reagent trifluoroacetic acid (TFA) results in a breakdown of the Fmoc-ene/-epoxide moieties. Notably, exposure to TFA in the presence of triisopropylsilane (TIS)/H2O/dithiothreitol (DTT) as scavengers leaves the Fmoc-ene alteration unscathed, whereas Fmoc-epoxide is ring-opened to the corresponding alcohol, suggesting that whether Fmoc-ene/-epoxide peptide truncations will remain unaltered will depend on synthesis and cleavage protocols used. As peptide drugs are subject to stringent quality requirements, varying the content of Fmoc-ene/-epoxide impurities coupled with synthesis/cleavage protocols impacting Fmoc alterations in a varying manner may pose challenges during downstream processing, warranting that due care is paid to the formation and reactivity of Fmoc-ene/-epoxide alterations.",
    url = "https://doi.org/10.1021/acs.oprd.5c00433",
    doi = "10.1021/acs.oprd.5c00433",
    openalex = "W7128503732",
    references = "doi101038s42004024012646"
}