Thermoelectric effects and dielectric polarisation in biopolymers

Eley, D. D.; Lockhart, N.C.; Richardson, C. N.

doi:10.1039/f19797500323

Cited by 24 publications

(7 citation statements)

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“…The possible motion of the whole NaDNA backbone, or part of it, and the previously reported dominance of long range motions of electrons and holes (Eley et al 1979) have been not observed in the results presented. This statement is supported by the following arguments:…”

Section: Discussioncontrasting

confidence: 53%

“…In contrast, some uncertainties seem to exist in analogous research on nucleic acid materials, * Correspondence to: J. Laud~t owing to the remarkable complexity of the system. Eley et al (1979) interpreted the Arrhenius temperature dependence of the d.c. conductivity (also with an exponential hydration dependence) as the intrinsic conductivity with electrons and holes as majority charge carriers. They observed protonic conductivity on samples with a water content higher than 25 wt%.…”

Section: Introductionmentioning

confidence: 99%

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Dielectric study of charge motion in DNA

Laudat

Laudát

1992

Eur Biophys J

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Abstract. The d.c. conductivity and daelectric properties of solid low-humidity NaDNA layers have been examined over frequency and temperature ranges up to 105 Hz and 80-330 K respectively. The results presented are basically consistent with a model in which the majority charge carriers are protons (H30 +, OH-) moving on the surface of a NaDNA chain in the neighbourhood of the phosphate groups. The increasing hydration also increases the mobility of counterions (Na +) and their contribution to a d. c. conductivity. The Arrhenius d. c. conductivity seems to be limited by electrochemical processes on the electrodes. Low-frequency dispersion is also caused by this effect. The local and long-range motion of charge carriers is limited below temperatures of a dipolar thermally stimulated depolarization current (TSDC) peak observed in the range 165-255 K. The amplitude and position of the peak depend strongly on the water content in the sample.

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Section: Discussioncontrasting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Dielectric study of charge motion in DNA

Laudat

Laudát

1992

Eur Biophys J

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“…Dielectric measurements (72,(89)(90)(91)(92) in the frequency range 10-4 Hz to I MHz fo r various po\ycrystalline proteins have revealed two dielectric dispersions, designated as the Q-and IX-dispersions shown in Figure 6. These dispersions move to higher frequencies as the protein hydration increases.…”

Section: Proton Conduction Effe Ctsmentioning

confidence: 99%

Protein-Water Interactions Determined by Dielectric Methods

Pethig

1992

Annu. Rev. Phys. Chem.

296

254

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KEY WORDS: dipole moment, enzymic activity, hydration, hydrogen bonds, orientational relaxation time, proton percolation INTRODUCTIONIn one of the earliest reports of the physicochemical properties of a protein, Sorensen (1) asked "Does crystallised egg-albumin contain water?" Fol lowing a detailed compositional analysis, he found that such samples contain about 0.22 g water per g water-free egg-albumin. In later work, he gives the water content of crystallized hemoglobin as 0.35 gjg (2). We now know that protein molecules can have from 0.20 to 0.70 g strongly associated (bound) water per g protein, and through modern x-ray and neutron diffraction studies, we have for some proteins a detailed knowledge of the location and bonding of much of this water (3-5). By using the latest high-resolution NMR techniques, we can even identify individual molecules of hydration water and characterize their binding sites on the protein molecule (6). Thus, in general and as a convenient method of classification, two kinds of water molecules associated with proteins have been identified: internal water and peripheral water. The internal water molecules, which form an integral part of a protein structure, diminish local charge-charge inter actions and reduce destabilizing effects that arise from otherwise unbonded proton donors and acceptors (7,8). These molecules exchange with bulk water in time scales ranging from tens of seconds to months (9, 10). As a rough gauge of the upper limit of internal water, we can consider the small 177 0066-426Xj92jll01-0l77$ 02.00 Annu. Rev. Phys. Chem. 1992.43:177-205. Downloaded from www.annualreviews.org by University of Sydney on 09/17/13. For personal use only.Quick links to online content Further ANNUAL REVIEWS 178 PETHIG enzyme pancreatic trypsin inhibitor (mol wt 6700), which contains fo ur internal waters (8). As this represents a hydration content of 1.07 wt%, we can conclude that most of the water bound to proteins is associated with the protein surface. Such hydration shells of peripheral water do not freeze upon cooling (11). And, although distinct nonrandom distributions of water molecules occur at the polar side-chains, consistent with the expected stereochemistry of the potential hydrogen-bonding sites (5), there is no evidence fo r the existence of extensive ice-like fo rmations of water molecules around protein molecules. Klotz (12) proposed that water might form clathrate-type structures around hydrophobic groups at protein sur faces. Evidence for this is found for the small, hydrophobic plant protein crambin, in which a cluster of pentagonal arrays, made up of 16 hydrogen bonded water molecules, sits at a hydrophobic intermolecular cleft (13).Of the approximately 90 water molecules per crambin molecule, 73 have been located (14), and all of them contribute to an ordered hydrogen bonded network around the protein surface. From NMR studies (6, and references cited therein), it appears that protein hydration is more dis ordered in solution than has been indicated from single crystal...

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“…Dielectric relaxation studies of hydrated protein powders have been reviewed by several workers. ,,− Different low-frequency relaxation processes (designated as Ω- and α-relaxations) have been studied as a function of hydration of the protein powders. To explain the relaxation process, a model-based percolation theory has been advanced. , These studies indicate that water acts as a plasticizer for the protein molecules…”

Section: A Dielectric Relaxation Of Aqueous Protein Solutionsmentioning

confidence: 99%