Document Type

Student Paper

Publication Date

2015

Disciplines

Geochemistry | Geology | Polymer Chemistry

Description, Abstract, or Artist's Statement

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. Contemporary enzymes are comprised of either organic or inorganic factors scaffolded by globular protein structure whereas we 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 differential. 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 variants of the clay montmorillonite (KSF and K10) were introduced into the polymerization milieu to observe its 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, has been shown to favor the formation 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.

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