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Protoenzymes: The Case of Hyperbranched Polymer-Scaffolded ZnS Nanocrystals

revised on 11.03.2020, 09:28 and posted on 11.03.2020, 09:43 by Irena Mamajanov, Melina Caudan, Tony Z. Jia

Enzymes could be described as small-molecule, metal, or cluster catalysts augmented by biopolymeric scaffolds. It is conceivable that early in chemical evolution, ancestral enzymes opted for simpler, easier to assemble scaffolds. Herein, we describe such possible protoenzymes: hyperbranched polymer-scaffolded metal-sulfide nanocrystals. Hyperbranched polyethyleneimine (HyPEI) and glycerol citrate polymer-supported ZnS nanocrystals (NCs) are formed in a simple, abiotically plausible process. Transmission electron microscopy (TEM) analyses of HyPEI-supported NCs reveals spherical particles with an average size of 10nm that undergo only a modest aggregation over a 14-day incubation. The polymer-supported ZnS NCs are shown to possess a high photocatalytic activity in an eosin B photodegradation assay, making them an attractive model for the study of the origin of life under the “Zn world” theory dominated by a photocatalytic proto-metabolic redox reaction network. The catalyst, however, could be easily adapted to apply broadly to different protoenzymatic systems.


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Tokyo Institute of Technology



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