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

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

“…(4) with m ϭ 4.4 and A ϭ 2.9 We have previously shown 8 that a similar dependence of the dielectric increment as a function of pH is evidenced both in the case of poly(␣-glutamate), where changes from randomly coiled (at f c ϭ 1) to rod-like helical structures (at f c ϭ 0) occur, and in the case of poly(␥-glutamate) where the polymer structure does not allow the formation of an helical structure. In Figure 4, the dielectric increments of poly-(glutamate) aqueous solutions are shown, compared with the values obtained by Mashimo et al 3,4,9 As can be seen, the apparent change of ⌬ with the fraction of the coiled part, according to the pH values, occurs even in poly(␥-glutamate) aqueous solutions, where to a decrease of pH it does not correspond any decrease of the coiled fraction in the polymer chain. A similar feature is found in the case of poly(lysine) (see Figure 2), where the dielectric increment of the three polymers of different chirality investigated varies with pH, independently of the possibility of the chain to assume a different configuration induced by pH.…”

“…This interpretation differs a somewhat from that proposed by Mashimo et al, 3,4,9 who assumed that the dynamics of side-chain motion could occur only when a repeating unit, carrying a polar ionizable group, belongs to a coiled section of the polymer chain, and that micro-Brownian motion or internal motion is prohibited in polymer chains that take helical structures. These authors 3,4,9 suggest that the intermediate observed dielectric dispersion, between that attributed to relaxation of bulk water and that involving counterions, could depend largely on the hydration water, being caused by orientational polarization of the bound water molecules in the vicinity of the polar groups. However, we have put forth the hypotheses that the dielectric dispersion could be essentially related to the progressive ionization of the charged groups that takes place upon changing the pH of the solution, rather than to a conformational transition from ␣-helix to random coil, induced by pH.…”

“…[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.…”

Globule-coil transition of denatured globular protein investigated by a microwave dielectric technique

“…As far as structural and dynamical studies are concerned, recently dielectric relaxation processes reflecting micro‐Brownian motions of polymer chains in aqueous solutions of poly (vinyl pyrrolidon) (PVP),26 poly(vinylmethylether) (PVME),27 and poly(gutamic acid) (PGA)28 were studied by dielectric relaxation measurements using time domain reflectometry (TDR) methods 29–32. Dielectric response functions obtained for chain motions are described by the Kohlrausch–Williams–Watts (KWW) type 33–36.…”

A method of measuring surface permittivity by microwave dielectric analysis

“…The devices are the same as that reported previously. 8,[11][12][13]18,19 Dielectric spectra of a water-Teflon system and a polyethylene-water system were measured by the TDR method in order to obtain the relationship between the cell design and the depth profile of permittivity.…”