סמינר בכימיה אורגנית: Chemical evolution: How did Chemistry Become Biology?

Abstract:

A long-standing challenge in origins of life research is to find plausible prebiotic routes for the formation of primordial polymers. Although the synthesis of various amino acids by prebiotic reactions is now generally accepted, their subsequent oligomerization into peptides is more difficult to explain. Recently, simplified routes for prebiotic peptide formation have been reported, which involve subjecting a mixture of amino acids together with either hydroxy acids or mercapto acids, to repetitive wet-dry cycles. It has been proposed that the resulting proto-peptides, containing both ester or thioester and amide linkages, might have constituted part of the primordial proto-peptide population. Today’s proteins can assemble into complex architectures. These assemblies increase the kinetic stability and attenuate hydrolysis rates. Hence, assembly could play a significant role in the synthesis-hydrolysis cycles and provide an advantage for the accumulation of assembled molecular species over others.

In our recent investigation we tested the hypothesis that assembly of proto-polymers could have contributed to the selection of certain building blocks over others during chemical evolution. We subjected mixtures of various building blocks, including amino acids, hydroxy acids, fatty acids and mercapto acids to continuous drying. Product mixtures were characterized by various methods including liquid chromatography mass spectrometry, electron microscopy, dynamic light scattering, and nuclear magnetic resonance spectroscopy. Our analysis of proto-polymer length, monomer composition, and assemblies reveals a structural shift that coincides with polymeric nature. Moreover, we observe that chemical evolution demonstrates stringent selection based on both kinetic and thermodynamic landscapes. Our results can shed new light on the way in which chemical evolution operates at the very fundamental level and guide future experiments of chemical evolution towards generation of functional polymers.