The framework of percolation theory is used to analyze the hydration dependence of the capacitance measured for protein samples of pH 3-10, at frequencies from 10 kHz to 4 MHz. For all samples there is a critical value of the hydration at which the capacitance sharply increases with increase in hydration level. The threshold h(c) = 0.15 g of water per g of protein is independent of pH below pH 9 and shows no solvent deuterium isotope effect. The fractional coverage of the surface at h(c) is in close agreement with the prediction of theory for surface percolation. We view the protonic conduction process described here for low hydration and previously for high hydration as percolative proton transfer along threads of hydrogen-bonded water molecules. A principal element of the percolation picture, which explains the invariance of h(c) to change in pH and solvent, is the sudden appearance of long-range connectivity and infinite clusters at the threshold h(c). The relationship of the protonic conduction threshold to other features of protein hydration is described. The importance of percolative processes for enzyme catalysis and membrane transport is discussed.

Proton percolation on hydrated lysozyme powders / G., Careri; Giansanti, Andrea; J. A., Rupley. - In: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - ISSN 0027-8424. - STAMPA. - 83:18(1986), pp. 6810-6814.

Proton percolation on hydrated lysozyme powders.

GIANSANTI, Andrea;
1986

Abstract

The framework of percolation theory is used to analyze the hydration dependence of the capacitance measured for protein samples of pH 3-10, at frequencies from 10 kHz to 4 MHz. For all samples there is a critical value of the hydration at which the capacitance sharply increases with increase in hydration level. The threshold h(c) = 0.15 g of water per g of protein is independent of pH below pH 9 and shows no solvent deuterium isotope effect. The fractional coverage of the surface at h(c) is in close agreement with the prediction of theory for surface percolation. We view the protonic conduction process described here for low hydration and previously for high hydration as percolative proton transfer along threads of hydrogen-bonded water molecules. A principal element of the percolation picture, which explains the invariance of h(c) to change in pH and solvent, is the sudden appearance of long-range connectivity and infinite clusters at the threshold h(c). The relationship of the protonic conduction threshold to other features of protein hydration is described. The importance of percolative processes for enzyme catalysis and membrane transport is discussed.
1986
01 Pubblicazione su rivista::01a Articolo in rivista
Proton percolation on hydrated lysozyme powders / G., Careri; Giansanti, Andrea; J. A., Rupley. - In: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - ISSN 0027-8424. - STAMPA. - 83:18(1986), pp. 6810-6814.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/495782
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