Dielectric Relaxation Sudies on Analogues of the Polypentapeptide of Elastin

Article abstract of DOI:10.1021/j100313a053

Dielectric measurements of the complex permittivity of coacervate concentrations of two analogues of the polypentapeptide of elastin, (Xxx¹-Pro²-Gly³-Val⁴-Gly⁵)m 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 degC.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_ε, of the librational mode of each polypetapeptide analogue increases with increasing temperature from near zero at 0 degC to approximately 40 at 60 degC, 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 clathare-like water surrounding hydrophobic side chains contributes to the high-frequency relaxation.