Solution behavior of synthetic silk peptides and modified recombinant silk proteins

Abstract

Spider dragline silk from Nephila clavipes possesses impressive mechanical properties derived in part from repetitive primary sequence containing polyalanine regions that self-assemble into crystalline beta-sheets. In the present study, we have sought to understand more details of redox responses related to conformational transitions of modified silk peptides and a recombinant protein containing encoded methionine triggers. Regardless of the position of the methionine trigger relative to the polyalanine domain, chemical oxidation was rapid and slight increases in the alpha-helical structure and decreases in the beta-sheet and random coil content were observed by CD and FTIR in the assembled silk-like peptides and the recombinant protein. CD results indicated that the decrease in beta-sheet and random coil conformations, coupled with the increase in helical content during oxidation, occurred during the first 30 min of the reaction. No further conformational changes occurred after this time and the response was independent of methionine trigger location relative to the penta-alanine domain. These results were confirmed with fluorescence studies. The design, processing and utility of these modified redox triggered silk-like peptides and proteins suggest a range of potential utility, from biomaterials to engineered surface coatings with chemically alterable secondary structure and, thus, properties.