Rotational and translational water diffusion in the hemoglobin hydration shell: dielectric and proton nuclear relaxation measurements

Abstract

The dynamic properties of water in the hydration shell of hemoglobin have been studied by means of dielectric permittivity measurements and nuclear magnetic resonance spectroscopy. The temperature behavior of the complex permittivity of hemoglobin solutions has been measured at 3.02, 3.98, 8.59, and 10.80 GHz. At a temperature of 298 K the average rotational correlation time tau of water within a hydration shell of 0.5-nm thickness is determined from the activation parameters to be 68 +/- 10 ps, which is 8-fold the corresponding value of bulk water. Solvent proton magnetic relaxation induced by electron-nuclear dipole interaction between hemoglobin bound nitroxide spin labels and water protons is used to determine the translational diffusion coefficient D(T) of the hydration water. The temperature dependent relaxation behavior for Lamor frequencies between 3 and 90 MHz yields an average value D(298K) = (5 +/- 2) x 10(-10)m2 s-1, which is about one-fifth of the corresponding value of bulk water. The decrease of the water mobility in the hydration shell compared to the bulk is mainly due to an enhanced activation enthalpy.

Simplified Methods for Calculating Cerebral Metabolic Rate of Oxygen Based on 17O Magnetic Resonance Spectroscopic Imaging Measurement during a Short 17O2 Inhalation

“…Saturation transfer electron paramagnetic resonance studies have shown that the c value for rotational motion of the hemoglobin molecule is 8 × 10 −6 seconds when the hemoglobin molecule is encapsulated within the erythrocyte membrane (Cassoly, 1982). This is approximately 10 6 times slower than the rotational correlation time of bulk water (10 −12 − 10 −11 s) (Steinhoff et al, 1993 In the modified "complete model" for 17 O MR measurements (Fig. 1B), the vascular compartment of arteriole is replaced by artery because of the approximately identical H 2 17 O contents in arteriole and artery.…”

In vivo17O NMR approaches for brain study at high field

“…If the c value of 8.5 Â 10 À12 s for bulk water at 298 K is used, 3 then estimated 17 O T 2 and T 1 according to eqn (2) should be between 2.8 ms (for ¼ 0) and 2.1 ms (for ¼ 1). This estimation indicates that the 17 O relaxation times of water are extremely short, in the range of few milliseconds.…”

Hydration analysis of Pseudomonas aeruginosa cytochrome c551 upon acid unfolding by dielectric relaxation spectroscopy

“…Such hydration water with the lowered DR frequency is called looselybound water or constrained water. So far, studies on the constrained water of proteins in aqueous solution were carried out to understand thermodynamic stability and functions of proteins such as myoglobin, ribonuclease A, hemoglobin, horse heart cytochrome c, bovine serum albumin, ovalbumin and ubiquitin [13][14][15][16][17][18][19]. Our studies on aqueous actin filament solutions demonstrated the presence of the hypermobile water in addition to the constrained water [20,21].…”