Dielectric measurements of the complex permittivity of coacervate concentrations of two analogues of the polypentapeptide of elastin, (Xxx1-Pro2-Gly3-Val4-Gly 5)n, where Xxx is Val for the elastin polypentapeptide and Ile and Leu for the two analogues, were taken over the frequency range 1-1000 MHz and over the temperature range 0-60°C. Two relaxation processes were observed in each polypentapeptide. One relaxation has a frequency centered in the low megahertz frequency range, which has been attributed to a low-frequency librational mode within the polypeptide. The other relaxation is located near the gigahertz frequency range. The magnitude of the dielectric increment, Δ∈, of the librational mode of each polypentapeptide analogue increases with increasing temperature from near zero at 0°C to approximately 40 at 60°C, showing an inverse temperature transition to a more ordered structure. Conversely, the magnitudes of the dielectric increment of the high-frequency relaxation decrease with increasing temperature and differ in approximate proportion to the hydrophobicity of the pentamer for the polypentapeptide of elastin and the two analogues at temperatures below the inverse temperature transition. It is suggested that clathrate-like water surrounding hydrophobic side chains contributes to the high-frequency relaxation.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry