Fourier Transform Infrared Spectroscopy (FTIR) was used to study the effects of a disordered peptide, GVTA, on the structure of VTAV, a peptide capable of forming beta sheets and aggregating. Protein aggregation is associated with neurodegenerative diseases such as Parkinson’s disease. GVTA and VTAV are peptides found within residues 71-82 of the natively unfolded protein alpha-Synuclein, a protein whose aggregation is associated with the onset of Parkinson’s disease. These residues are of interest because their deletion from the full-length alpha-Synuclein has been shown to prevent misfolding. Previous work in our lab has shown that GVTA is able to disrupt beta sheet formation in VTAV when both samples have a concentration of 0.1 M.<br/>Here we present data where the 1:1 concentration ratio between GVTA and VTAV is maintained but the concentrations of the two peptides is varied. The data was fit to the sum of four pseudo-Voigt bands to quantify the amount of beta sheet present at each concentration. As the concentration in the mixture increases, the percent beta sheet decreases indicting that the peptides have become more disordered in spite of the fact that GVTA still only represents 50% of the total amount of peptide in the mixture. This is surprising, as one might expect that the beta sheets in VTAV would be more stable at higher concentrations where inter-peptide interactions would be more prevalent.<br/>Further experiments mixed 0.1M VTAV and varying concentrations of GVTA are studied in a series of temperature dependent experiments to evaluate the effectiveness of GVTA at disrupting beta sheet. Mathematical averages of the two peptides in isolation are compared to experimental mixtures using Microcal Origin, to determine the effects of interaction between the two peptides. As the concentration of GVTA decreases relative to the concentration of VTAV, GVTA becomes less effective at preventing beta sheet formation.<br/>To determine whether the disaggregation was the result of macromolecular crowding, or due to a specific interaction between the two peptides, we compared the mixture of VTAV and GVTA to a mixture of VTAV and Ficoll, a compound commonly used as a “crowding agent”. Our experimental results with Ficoll mixtures match the mathematical average, indicating crowding alone cannot prevent beta sheet formation in VTAV.

Effects of a small peptide on VTAV aggregation

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.