THE EFFECTS OF CLAY ON GLYCEROL/CARBOXYLIC ACID POLYMERIZATION: IMPLICATIONS OF MINERAL CONTROLS ON PREBIOTIC CHEMISTRY

Proto-enzymatic catalysis on early Earth is an important consideration in prebiotic chemistry research as it leads to the understanding of the emergence of the metabolic reaction networks, and, ultimately, complex life. Contemporary enzymes are composed of either organic or inorganic factors scaffolded by globular protein structure. In this study, I consider hyperbranched polyesters as a possible extant scaffold that is easier assembled than the peptide one. The goals of this project are to consider prebiotically plausible starting materials for such structure formation utilizing a subset of conditions for polymer synthesis involving the presence of mineral surfaces as well as temperature and hydration differentials. As likely candidates for the formation of hyperbranched polyesters on early Earth, reactions of glycerol with certain carboxylic acids (citric, tartaric, succinic, and fumaric) were studied. Two synthetic variants of the clay montmorillonite (KSF and K10) were introduced into the polymerization milieu to observe their effects in the process. To monitor polymer growth, their weights were taken at hourly intervals to ascertain water loss due to the condensation-dehydration reaction of the polyesterification. To characterize the resulting polymers’ structures, acid-base titrations were performed to estimate the number of acid groups esterified during the experiment. Size-exclusion chromatography coupled with mass spectrometry was also used to elucidate the polyester structure and degree of branching. The presence of the clays was found not to affect the number of ester bonds formed or the kinetics of the polymerization product. The addition of clay, however, favored the formation of certain polymer conformations. These preliminary results indicate a potential selective pressure that clay minerals introduce into the chemical evolution of the hyperbranched polyester enzyme scaffolds and thus the advent of complex life.