Cyanamide mediated syntheses under plausible primitive earth conditions

Abstract

Peptides were formed in yields of 5%, 17% and 66%, respectively, when aqueous solutions of glycine, isoleucine or phenylalanine were dried and heated for 24 h at 90 degrees C with adenosine 5'-triphosphate, 4-amino-5-imidazolecarboxamide and cyanamide. Glycine and L-phenylalanine produced mixtures of di-, tri- and tetrapeptides, while L-isoleucine gave only the dipeptide in detectable quantities. The dipeptides of L-isoleucine and L-phenylalanine were identified by mass spectrometry and enzymatic and enzymatic degradation.

Diketopiperazine-mediated peptide formation in aqueous solution

“…A number of experiments concerning prebiotic peptide formation have been performed under various conditions with amino acids, though some of which seem to have been possible only at special areas on the primitive Earth, or by the use of amino acid derivatives or activated amino acids (Harada and Fox, 1958;Fox and Harada, 1960;Guidry, 1960, 1961;Paecht-Horowitz and Katchalsky, 1967;Lewinsohn et al, 1967;Sawai and Orgel, 1975;Nooner et al, 1977;Orgel, 1978, 1979a, b;White and Erickson, 1980;Yanagawa et al, 1984;Yanagawa and Kojima, 1985). However, it seems more likely to us that the chemical evolution might have taken place in the primitive oceans as a more universal place where peptides were formed from amino acids with an aid of various condensing agents and were accumulated gradually against their hydrolysis under mild conditions.…”

Cyanamide mediated syntheses of peptides containing histidine and hydrophobic amino acids

“…A portion of the putative peptides of the various reactions, isolated by TLC as described in 2.2, together with appropriate standards were hydrolyzed with Carboxypeptidase A by a modification of the procedure used by Nooner et al (1977): 0.1 ml of an 0.2 mmole lithium chloride solution of Caxboxypeptidase A (1 unit) was added to 1 ml of 0.03 mmole Tris buffer (pH 7.5) containing 0.5 mmoles sodium chloride and 0.2 -0.5 #mole peptide. The mixture was incubated at 22°C for 16 to 24 h, evaporated under nitrogen to 100 #1 and an aliquot analyzed by TLC.…”

“…In addition, hydrolysis of cyanamide is relatively slow; an aqueous solution of cyanamide (pH 6.8) was unchanged after five days of heating at 65°C (Halmann 1968). Also, the best yields of peptides in cyanamide mediated synthesis occur by evaporation of aqueous reaction mixtures and heating at moderate temperatures (Nooner et al 1977). Therefore, a primeval evaporating pond model could have served as the means by which cyanamide participated in prebiotic condensation reactions under plausible primitive Earth conditions.…”

“…Cynamide has been used under mild aqueous conditions to achieve peptide synthesis (Ponnamperuma and Peterson 1965;Halmann 1968) but with low yields. It has been found to be more effective under evaporating conditions at moderate temperatures Nooner et al 1977) in promoting peptide synthesis. It has also been used in a variety of other possible prebiotic condensation reactions, such as the synthesis of deoxythymidine oligonucleotides , the synthesis of acylglycerols (Eichberg et al 1977), the synthesis of phosphatidic acids , and the phosphorylation of nucleosides with apatite (Schwartz 1972).…”

“…Therefore, a primeval evaporating pond model could have served as the means by which cyanamide participated in prebiotic condensation reactions under plausible primitive Earth conditions. Previous work in this laboratory Nooner et al 1977) has shown that a system of 4-amino-5-imidazole carboxamide (AICA), adenosine 5'-triphosphate (ATP), amino acid, and cyanamide will condense amino acids to peptides. This was also observed if ATP was omitted.…”