Of the 3 main protein secondary structures, β-sheets have proven the hardest to model and study. Although a number of model systems have been explored for creating β-sheets, they have been plagued by problems of aggregation and insolubility. These problems can be traced to the flat, two-dimensional shapes of the existing models systems, which allow for the model β-sheets to associate either side to side, or above and below, or both. To prevent such aggregation and improve solubility, a model system that includes a 3-dimensional shape might be useful. Research has shown that 1 has a rigid conformation with the two alkyne ligands spaced 3.3 A apart, which is close to the spacing of the two peptide strands in a β-sheet. Current work has been exploring whether peptides appended to the two alkynes in the rigid, bimetallic ring 1 will associate with each other to form β-sheets, as indicated in 2. It has been found that placing a phenyl spacer between the alkynes and the peptides prevents the formation of intramolecular hydrogen bonds between the two peptides, but a methylene spacer does allow for this intramolecular hydrogen bonding. Whether the methylene spacer is attached to a primary amine or a carboxyl group does affect the nature of the hydrogen bonding. The conformations of these species have been explored using both spectroscopic and DFT experiments, and the data indicates that these molecules adopt a conformation that has the peptides in a β-sheet conformation with the ferrocene rings located above the nascent sheet. This gives the model a unique 3-dimensional shape. Details regarding the preparation and behavior of these novel bioorganometallic models for β-sheets will be detailed.

Using a rigid, organometallic ring system to nucleate β-sheets

ACS Fall 2020 Virtual Meeting

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