title: Photosensitizing effect of cations on amino acids and peptides.
abstract: In connection with a study of the chemical evolution of abiogenically synthesized organic compounds on primitive Earth and the physical conditions of other planets, this paper reports the experimental results obtained by the photolysis of solutions of aliphatic amino acids (glycine, alanine, valine, leucine, n. leucine) and peptides in the atmosphere of the air, N2, Ar and CO2 in the presence of the most simple photocatalyzers-cations of sulphates. The evidence shows that the photochemical conversion of NH2 acids depends on the content of the atmosphere. The decay of NH2-group is most active in air. N2 and Ar exert no significant influence on deamination, whereas in the atmosphere of CO2 the formation of ammonia in valine, for example, was only 29 per cent of its total amount during photolysis in the air. Cu2+ and Fe2+ catalyzed while Al3+ inhibited the ammonia excretion. The formation of acetaldehyde during alanine photolysis was actually independent from the atmosphere of N2 and was inhibited in Ar and CO2. Oxydative processes inducing the formation of glyoxalic acid and formaldehyde were sharply inhibited in Ar, N2 and CO2. Under the influence of ultraviolet light of the decay of NH2-acids is also accompanied by the formation of new NH2-acids. The photosensitizing effect of cations induces a rupture of -CO-NH-bonds in peptides and, provided heavy radiation doses, prevents the formation of new NH2-acids. The longer the dipeptide chain, the more significant the quantum yield of its decomposition. The photolysis of dipeptides, leading to their decay, does not necessarily induce a hydrolytic rupture of -CO-NH-bonds resulting in the formation of three amino acids. The results obtained permit approaching problems concerning the effect of the gas content of the atmosphere and various cations (photocatalyzers) on photolytic conversion of abiogenically synthesized and biogenically significant substances, amino acids for example, at the action of ultraviolet light.
authors.affiliation: USSR.
authors.forename: N P
authors.initials: NP
authors.lastname: Bogdanova
authors.forename: M A
authors.initials: MA
authors.lastname: Khenokh
mesh_terms: D000388:Air; D000535:Aluminum; D000596:Amino Acids / Q000138:chemical synthesis* / Q000737:chemistry*; D001128:Argon; D001272:Atmosphere / Q000737:chemistry; D002245:Carbon Dioxide; D002412:Cations; D003300:Copper; D018559:Exobiology; D007501:Iron; D008345:Manganese; D009584:Nitrogen; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry*; D010777:Photochemistry; D010782:Photolysis; D015032:Zinc
chemical_list: D000596:Amino Acids; D002412:Cations; D010455:Peptides; D002245:Carbon Dioxide; D008345:Manganese; D001128:Argon; D003300:Copper; D000535:Aluminum; D007501:Iron; D015032:Zinc; D009584:Nitrogen