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Microwave dielectric studies on proteins, tissues, and heterogeneous suspensions
Author(s) -
Foster Kenneth R.,
Schepps Jonathan L.,
Epstein Benjamin R.
Publication year - 1982
Publication title -
bioelectromagnetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.435
H-Index - 81
eISSN - 1521-186X
pISSN - 0197-8462
DOI - 10.1002/bem.2250030108
Subject(s) - dielectric , relaxation (psychology) , bound water , microemulsion , conductivity , chemistry , microwave , viscosity , dielectric loss , solvent , materials science , thermodynamics , water of crystallization , permittivity , chemical physics , analytical chemistry (journal) , nuclear magnetic resonance , chromatography , organic chemistry , composite material , molecule , pulmonary surfactant , biochemistry , physics , psychology , social psychology , optoelectronics , quantum mechanics
We summarize the results of several of our recent studies on the dielectric properties of protein solutions, tissues, and nonionic microemulsions at microwave frequencies extending to 18 GHz. The data in all cases are analyzed using the Maxwell mixture theory to determine the dielectric properties of the suspending water and the amount and dielectric properties of the water of hydration associated with the suspended phase. The dielectric data from the protein solutions and tissues are broadly consistent with the results of previous studies at UHF frequencies; they indicate hydration values in the range of 0.4–0.6 g water/g protein. There is evidence of a dielectric relaxation process occurring at low‐GHz frequencies that can be attributed in part to dielectric relaxation of the “bound” water in the system. The remaining solvent water appears to have dielectric properties close to, if not precisely the same as, those of pure water. The average relaxation frequency of the suspending water in the microemulsions is reduced from that of pure water, evidently reflecting an average of that of the water of hydration (∼5–6 GHz) and that of pure water. This reduced average relaxation frequency implies an increased average viscosity of the water and (by Walden's rule) accounts for the unexpectedly low ionic conductivity of the preparations.