Dielectric behavior of water in biological solutions: Studies on myoglobin, human low‐density lipoprotein, and polyvinylpyrrolidone

Abstract

The dielectric behavior of the aqueous solutions of three widely differing macromolecules has been investigated: myoglobin, polyvinylpyrrolidone (PVP), and human serum low-density lipoprotein (LDL). It was not possible to interpret unambiguously the dielectric properties of the PVP solution in terms of water structure. The best interpretation of the dielectric data on the myoglobin and LDL solutions was that, in both cases, the macromolecule attracts a layer of water of hydration one or two water molecules in width. For LDL, this corresponds to a hydration factor of only 0.05 g/g, whereas for myoglobin the figure is nearer 0.6 g/g. With myoglobin, part of the water of hydration exhibits its dispersion at frequencies of a few GHz, and the rest disperses at lower frequencies, perhaps as low as 10-12 MHz. The approximate constancy of the width of the hydration shell for two molecules as dissimilar in size as LDL and myoglobin confirms that the proportion of water existing as water of hydration in a biological solution depends critically on the size of the macromolecules as well as on their concentration.

Modeling of dielectrophoretic transport of myoglobin molecules in microchannels

“…The thickness of the electrodes is assumed to be very small as compared to the height of channel, and hence neglected in the simulations. The dielectric properties of the myoglobin and aqueous solution considered for the analysis 48 are given as p = 83.5 o , m = 78.5 o , p = 0.01 S / m, and m = 0.065 S / m. Here 0 = 8.854ϫ 10 −12 C 2 N −1 m −2 is the permittivity of free space. The simulations are conducted at applied voltages of 1-100 V at different frequencies.…”

“…Myoglobin is a single chain globular protein of 153 amino acids containing heme ͑iron containing porphyrin͒ prosthetic group in the center, around which remaining apoprotein folds. [43][44][45][46][47][48][49] It has molecular weight of 16.7 kDa. [44][45][46]48 It is the primary oxygen carrying pigment of muscle tissues.…”

“…[43][44][45][46][47][48][49] It has molecular weight of 16.7 kDa. [44][45][46]48 It is the primary oxygen carrying pigment of muscle tissues. Myoglobin has isoelectric point at pH 8.5, 3 where it acts as a neutral particle.…”

“…Later, based on x-ray studies, myoglobin molecule represented as an oblate spheroid of axial ratio 2:1. 44 Further, Grant et al 48 modeled the myoglobin molecule as a spheroidal shape with radius of 1.53 nm surrounded by a uniform shell of bound water with thickness of 0.35 nm. To the best of authors' knowledge, there is no universally accepted exact shape of the myoglobin molecule due to its globular structure.…”

“…According to Grant et al, 48 the volume of myoglobin is 15.0025 nm 3 . Based on this volume, the geometry of the different shapes of myoglobin is modeled as ͑i͒ a = b = c = r = 1.53 nm ͑for sphere͒, ͑ii͒ a = b = 1.9276 nm, c = 0.9638 nm ͑for oblate spheroid͒, and ͑iii͒ a = 2.4287 nm and b = c = 1.2144 nm ͑for prolate spheroid͒.…”