Chemical Evolution: An Approach Involving Molecular Interactions

The processes by which the first self-replicating systems arose through different stages from a milieu of racemic mixtures of biomolecules, obtained through prebiotic organic synthesis, constitute the least understood link in the evolutionary history of the biosphere. An approach primarily involving molecular interactions observed in crystals, towards understanding these processes is discussed. Amino acids and peptides have a strong intrinsic propensity to arrange themselves in such a way as to bring the main chain amino and carboxylate groups into periodic hydrogen bonded proximity. The geometrical condition for the nonenzymatic condensation is satisfied in these arrangements. It appears that chiral separation could be achieved in favourable cases through molecular interactions. The primitive molecular assemblies which gave rise to early self-replicating systems could have been similar in nature to the self-assembly systems, generated by noncovalent interactions, which occur at the lowest levels in the organisational heirarchy of present day organisms. Thus, the study of biologically significant non-covalent interactions, including specific ones, is important for understanding not only the present biosystems but also the primitive biomolecular assemblies. In addition to their probable relevance to prebiotic phenomena, the investigations discussed here have led to results which are of intrinsic interest in relation to biornolecular aggregation and interactions