Conformational Switching Between 310, α and ∏-helical States in a 12 Amino Acid Long Peptide Studied by Time-resolved Fluorescence and CD Spectroscopy
(English)Article in journal (Refereed) In press
We have measured the end-to-end distance of a small peptide using time-resolved fluorescence energy transfer experiments and CD spectroscopy at various concentrations of TFE. The peptide comprises tryptophan as the donor and nitrotyrosine as the acceptor. The results show that the peptide is to a large degree helical even in the absence of TFE, and that addition of TFE to the solutions favors short, α-helical structures. Because of the nanosecond time resolution in the time-resolved fluorescence experiments, we are able to resolve four groups of donor–acceptor distances. The distances themselves do not change much with addition of TFE, however, the populations of the subgroups changes with TFE concentration. We assign the four resolvable distances to be, in decreasing length order, two forms of elongated, 310-helical structures, π-helical, and α-helical structures. The presence of multiple helical forms is supported by the fact that at least three components are needed to describe the change in CD upon addition of TFE. As we are observing the peptide under equilibrium conditions, the results tell that the peptide is at all TFE concentrations undergoing length changes, which are also accompanied by changes in hydration/solvent exposure. Addition of TFE does not appear to change the peptide structures, but changes the energy landscape in favor of short, α-helical structures.
Time-resolved fluorescence spectroscopy, CD spectroscopy, conformational dynamics
IdentifiersURN: urn:nbn:se:uu:diva-109392OAI: oai:DiVA.org:uu-109392DiVA: diva2:272259