Further observations on the electrical properties of hemoglobin-bound water

Abstract

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.

Statistical Time Events in Enzymes: A Physical Assessmen

“…74 A possible explanation of these relaxations involves the relaxation of bound water in qualitative agreement with the results obtained in hydrated protein powders. 3 7 -3 9 However, the possibility exists that these relaxations originate from the displacement of protons which are fluctuating among the different sites, because of the Kirkwood-Schumaker effect.…”

Temperature effects on soil bulk dielectric permittivity measured by time domain reflectometry: A physical model

“…Although a detailed description of dielectric relaxation for each molecular layer of bound water may be feasible, critical information regarding these complex interactions with TDRmeasured composite waveforms (i.e., considering each molecular layer) are lacking, thereby limiting the applicability of such analysis. We have opted for an alternative approach whereby water layers having dielectric relaxation frequencies lower than a certain cutoff frequency (f*) are considered as bound water having lower dielectric permittivity than for bulk water [Bockris et al, 1966;Pennock and Schwan, 1969]. Thus the simplified modeling approach uses a single cutoff dielectric relaxation frequency to distinguish between bound and free (bulk) water.…”

Local Flexibility in Molecular Function Paradigm

“…Subnanosecond dynamics of proteins studied by NMR (3), nitroxide spin labeling (4), dielectric relaxation (5), and fluorescence experiments (1) have advanced such descriptive terms as "breathing" (6), "relaxation," "segmental motion," and "mobile defect" (7) to portray the conformational mobility of proteins in functionally competent states. The presence of substantial Ͼ1-Å breathing motions has been recognized in early NMR studies on the flipping of the buried aromatic residues in the pancreatic trypsin inhibitor (8).…”