Solutions of horse hemoglobin of varying concentrations (7.5-26.6 g of Hb/100 cc) were prepared from crystallized Hb. Measurements of the complex dielectric constant of these solutions were made in the frequency range of 1-1200 MHz. This dielectric behavior is described in terms of the dipolar nature of the molecule, the dipolar nature of side chains extending out from the surface, and by a relaxation of a shell of water bound to the surface. The amount of bound water leading to the most reasonable dielectric behavior is 0.2 ± 0.05 g/g of Hb. This bound water is characterized by a change of enthalpy of abou t7 kcal/mol and a characteristic frequency of 500-1000 MHz.
The dielectric constant and conductivity of lecithin and diacetyllecithin solutions were determined at several concentrations in solvents of differing dielectric constant and at frequencies from 0.5 to 250 MHz. These data were shown to fit the general formula e* = e " + (eo -)/{l + [/(///c)]1_"i> where e* is the complex dielectric constant, eo and are the lowand high-frequency dielectric constants, f is the frequency, fc is a generalized characteristic frequency, and a is a constant, 0 < a < 1. A linear dependence of the low-frequency dielectric constant on concentration was also found. These two results permitted a complete description of the data in terms of characteristic frequency and dielectric increment which are indices of molecular size and dipole length. The values for these parameters were consistent with the known structure of lecithin in high dielectric constant media (e > 30). However, the dielectric increment was found to decrease with decreasing solvent dielectric constant. This is interpreted as an increase in dipole-dipole interaction to produce small molecular aggregates.
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