Plural origins of molecular homochirality in our biota Part II. The relative stabilities of homochiral and mixed oligoribotides and peptides.
By computer simulations--molecular mechanics and molecular dynamics with the amber force field (Weiner et al, (1986), J. Comp. Chem. 7, 230-252)--we have determined the stabilities of oligoribotide strands built with D- and L-riboses, and of peptide chains with D- and L-amino acid residues. In particular, complementary double-chains of oligoribotides were studied, since they are an important feature of the growing mechanism of modern nucleic acids. Peptide chains on the other hand, grow without need of a template. We found that mixed oligoribotides are less stable than homochiral ones, and that this chiral effect is less noticeable in peptide chains. The results support the interpretation that L-riboses act as terminators to the template-assisted growth of oligo-r-GD (enantiometric cross-inhibition; Joyce et al., (1987), Proc. Natl. Acad. Sci. USA 84, 4398-4402). Based on this effect, a chemical pathway is proposed which could, under assumed prebiotic conditions, bypass the hindrance of homochiral growth.
Soares
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Departamento de Química Fundamental, Universidade Federal de Pernambuco, Brasil.
Lins
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Longo
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Garratt
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Ferreira
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D004247:DNA / Q000737:chemistry*; D004355:Drug Stability; D007536:Isomerism; D008957:Models, Genetic; D009690:Nucleic Acid Conformation; D009843:Oligoribonucleotides / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D012266:Ribose / Q000737:chemistry*; D013237:Stereoisomerism
D009843:Oligoribonucleotides; D010455:Peptides; D011506:Proteins; D012266:Ribose; D004247:DNA