On the dielectric properties of poly(glutamic acid) in aqueous solution in the frequency range 107-1010 Hz

Abstract

The permittivity spectra of aqueous poly(g1utamic acid) and adenosine triphosphate solutions have been measured by the dielectric time domain spectroscopy technique in the frequency range of 20 MHz to 5 GHz. No evidence of a reported dispersion in the 100-MHz region due to side-group motions in poly-(glutamic acid) was found. It is demonstrated experimentally and shown theoretically that the premature truncation of time domain line shapes may introduce seeming dispersions, the frequency region of which will depend on the time window used. IntroductionDielectric spectroscopy is well established as a tool for studying proteins in solution.lP2 The &dispersion observed in the megahertz range has been attributed to molecular reorientation, and the dipole moment can be calculated from the corresponding dielectric increment. In addition, the dielectric relaxation times give information on the structure, the physical dimensions of the proteins being related to this relaxation time.As model system for proteins, synthetic polypeptides have been intensively studied by using different physical techniques. The dielectric dispersion due to side-chain motion in polypeptides in dioxane solution has been investigated by the dielectric time domain spectroscopy (TDS) m e t h~d .~,~ Relaxation times in the range 0.02-0.5

Dielectric study on molecular motions of poly(glutamic acid) in aqueous solution over a frequency range of 105-1010 Hz

“…If the polymer is a rodlike polymer, we get ( |, (0) |"(0) = µ"2( cos2 0)0|,(í;n) (11) where 0 is the angle between the helical axis and the parallel component of each dipole. In the case of PGA, it changes from the randomly coiled polymer at fc = 1 to the rodlike polymer at /c = 0, and its fraction of the coiled part changes accordingly with the pH value.…”

High-frequency dielectric study of side-chain dynamics in poly(lysine) aqueous solutions

“…[1][2][3][4] Dielectric spectroscopy in the high-frequency region (up to some GHz) has been extensively used to characterize the dielectric relaxation due to dipolar orientational polarization associated the with side-chain dynamics. [5][6][7] In an our recent work, 8 we have investigated the high-frequency dielectric properties of two different polypeptides [poly(␣-glutamate) and poly(␥-glutamate)] in aqueous solutions, and the observed dielectric dispersion, located at about 50 -100 MHz, has been attributed to the micro-Brownian motion of the side-chain groups along the chain of these polymers.…”

Dielectric Relaxation of Binary Mixtures of Glycerol with Three Monohydric Alcohols

“…On the other hand, looking from the complementary side, the fall in the normalized relaxation strengths of two of the B components, namely nB and rB (Fig. 3), indicates a structure breaking effect of Gly on these self-associating mono-alcohols, an explanation which has similarly been given for the addition of diols to normal alcohols [2]. A tendency to form hetero-complexes with a molar A : B ratio of about 1.3 may be inferred from the plots.…”