A periodic system of chiral structures in molecular biology

Abstract

A systemic regularity of molecular biology is considered: the tendency towards alternating of the sense of chirality of intramolecular structural levels of DNA and proteins, namely, D–L–D–L for DNA and L–D–L–D for proteins, is observable starting from the level of asymmetric carbon in deoxyribose and amino acids. Helicity is a special case of chirality. In intermolecular interactions, the sense of chirality of the highest intramolecular structural level directly involved in the interaction prevails in each of the participants. The interaction of molecules of the same nature (protein–protein, DNA–RNA, tRNA–mRNA, and ribozymes) mainly occurs in the case of the same sense of chirality, either L–L or D–D, and for molecules of different types (DNA–protein, tRNA–amino acids, and enzyme–substrate), in the case of different senses of chirality, either D–L or L–D. An alternating sense of the chiral hierarchy of conjugated levels of macromolecular structures in proteins and nucleic acids is of general biological importance: it determines the discreteness of levels, serves as a tool of folding, and provides a structural basis for “preferred collective” (or “macroscopic mechanical”) degrees of freedom in the design of macromolecular machines, as well as being one of the mechanisms of blockwise/saltatory development of the evolutionary process. A new fundamental concept is proposed: the homochirality of primary structures of DNA and proteins determines the amount of the entropic component of the free energy, which is used in the processes of folding and molecular rearrangements.