Electrostriction in Polyelectrolyte Solutions

The role played by electrostriction at biological polyelectrolytes, such as proteins and nucleic acids, has already been considered long ago. Cohn and Edsall (1943) concluded that due to the charged groups that ovalbumin contains, electrostriction reduces its specific volume by 2.43 % relative to the value calculated from its amino acid content (McMeekin and Maeshall 1952). The specific volume of rabbit myosin, rabbit tropomyosin, and Pinna tropomyosin (three muscle proteins) in water measured by Kay (1960) indicated a volume contraction by 0.028, 0.040, and 0.030 cm g respectively. These volume reductions were ascribed to electrostriction and were proportional to the number of charged groups (Mauzerall et al. 2002) in the proteins 270, 376, and315perl05g. 

Mauzerall et al. employed pulsed photoacoustic measurements on the proteins involved in bacterial photosynthesis and applied the Drude-Nernst equation to estimate 

However, they used the compressibility kt of the protein rather than that of water, ktw that the equation requires. The calculated electrostriction of — 0.030 nm /pair of ions is compatible with an assumed compressibility of 0.170 GPa (that of water is 0.453 GPa ) and a relative permittivity in the immediate vicinity of the protein of4 l. 

The charges on the walls of ion channels (see Sect. 5.3.3) and the ions passing through them also cause electrostriction of the water, as discussed by several authors 

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