Elastin-like Peptide in Confinement: FT-IR and NMR T 1 Relaxation Data

Abstract

Abstract We employed FT-IR and NMR experiments to investigate the influence of a cell-mimicking crowding environment on the structure and dynamics of an elastin-like peptide (ELP) with the sequence GVG(VPGVG)3, which – due to a high number of hydrophobic amino acid side chains – exhibits an inverse temperature transition (ITT). As simplified crowding agent, we used 30 wt% Ficoll. The FT-IR data revealed the well-known broad ITT above ~25°C, as observed by the decrease of the relative population of random coil structures and the concomitant increase of type II β-turns. Interestingly, the addition of Ficoll leads to a destabilizing effect of type II β-turn structures. This is in contrast to the expected excluded-volume effect of the macromolecular crowder, but can be explained by weak interactions of the peptide with the polysaccharide chains of the crowding agent. Further, the crowding agent leads to the onset of a reversal of the folding transition at high temperatures. The full assignment of the ELP allowed for a residue-specific investigation of the dynamic behavior of ELP by NMR. Due to a strong change of microscopic viscosity between native/buffered conditions and crowded conditions, relaxation data remain inconclusive with respect to the observation of an ITT. Hence, no quantitative details in terms of internal conformational changes can be obtained. However, temperature dependent differences in the 13C relaxation behavior between core and terminal parts of the peptide indicate temperature induced changes in the internal dynamics with generally higher internal mobility at chain ends: This is in full agreement with FT-IR data. In harmony with the FT-IR analysis, macromolecular crowding does not lead to significant changes in the relaxation behavior.