Serine clusters studied by atmospheric pressure ionization mass spectrometry and their implications for the origin of biomolecule homochirality
Noncovalent interactions strongly influence the three-dimensional conformation of biomolecules, providing structural properties that allow the biochemical selectivity that underlies biological activity. Chirality plays a major role in biological systems; the high selectivity of biochemical reactions that drive processes necessary to sustain life requires homochiral biopolymers (composed of L-amino acids and D-sugars). A protein synthesized with a random composition of amino acid enantiomers could not have the specificity needed to function. The emergence of homochirality continues to be one of the most challenging topics associated with the origin of life. One possible scenario is that aggregates of amino acids might have been involved in a sequence of chemical events that led to chiral biomolecules in replicating systems, viz. to homochirogenesis. Noncovalent interactions between free amino acids have been studied by electrospray ionization mass spectrometry, revealing that clusters of free amino acids, particularly serine, exhibit a preference for homochirality. Serine is the amino acid of principal interest, since it forms magic number clusters composed of eight amino acid units, which have a remarkable preference for homochirality. These serine octamer clusters, (Ser8), react in enantioselective ways with other biomolecules. These observations have led to the hypothesis that serine octamers were responsible for the first chiral selection which was then passed via chemical reactions to other amino acids, saccharides, and peptides. The study suggests that (i) biomolecular homochirality may have originated from interactions between free amino acids, and (ii) the chiral choice of biopolymers (L-amino acids and D-sugars) may simply represent information written within the chemical structure of the individual residues.
Cooks, Purdue University.
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