Characterization of Globular Protein Solutions by Dynamic Light Scattering, Electrophoretic Mobility, and Viscosity Measurements

Abstract

In this work, physicochemical properties of two globular proteinsbovine serum albumin (BSA) having a molecular weight of 67 kDa and human serum albumin (HSA) having a molecular weight of 69 kDawere characterized. The bulk characteristics of these proteins involved the diffusion coefficient (hydrodynamic radius), electrophoretic mobility, and dynamic viscosity as a function of protein solution concentration for various pH values. The hydrodynamic radius data suggested an association of protein molecules, most probably forming compact dimers. Using the hydrodynamic diameter and the electropheretic mobility data allowed the determination of the number of uncompensated (electrokinetic) charges on protein surfaces. The electrophoretic mobility data were converted to zeta potential values, which allowed one to determine the isoelectric point (iep) of these proteins. It was found to be at pH 5.1 for both proteins, in accordance with previous experimental data and theoretical estimations derived from amino acid composition and p K values. To determine further the stability of protein solutions, dynamic viscosity measurements were carried out as a function of their bulk volume concentration for various pH values. The intrinsic viscosity derived from these measurements was interpreted in terms of the Brenner model, which is applicable to hard spheroidal particles. It was found that the experimental values of the intrinsic viscosity of these proteins were in good agreement with this model when assuming protein dimensions of 9.5 x 5 x 5 nm3 (prolate spheroid). The possibility of forming linear aggregates of association degree higher than 2 was excluded by these measurements. It was concluded that the combination of dynamic viscosity and dynamic light scattering can be exploited as a convenient tool for detecting not only the onset of protein aggregation in suspensions but also the form and composition of these aggregates.

Taylor Dispersion of Inorganic Nanoparticles and Comparison to Dynamic Light Scattering and Transmission Electron Microscopy

“…In contrast, the values from TDA were obtained without any difficulty, even in the presence of large dust particles, which agrees with previously reported literature values from Jachimska et al and confirms that the instrumentation used in this study is comparable to previously performed studies [9,10,30]. DLS is usually performed using a given laser wavelength, while the TDA measurements rely on selective wavelength detection.…”

“…Colloid and Interface Science Communications 22 (2018) [29][30][31][32][33] mean that the obtained results from TEM, TDA and DLS cannot be compared, on the contrary, yet the reader should keep in mind that the values are obtained by different techniques based on different models and assumptions. With this in mind, we show both results obtained via cumulant and CONTIN analysis for DLS measurements [29].…”

“…Colloid and Interface Science Communications 22 (2018) [29][30][31][32][33] are the mean values gathered from the instruments, with the corresponding standard deviations representing the instrumental reproducibility. Concerning the averages gathered by DLS, these are intensityweighted values.…”

The effect of protein concentration on the viscosity of a recombinant albumin solution formulation

“…43 The tted intrinsic viscosity value of $6.9 agreed with the reported aspect ratio of albumin, known to be a prolate ellipsoid. 8,15,40 Altogether, these observations along with those previously made from the Ross-Minton model, point to a difficulty in prediction of solution viscosity of concentrations > 350 mg mL À1 (see Fig. 6 (green line) and 7A (blue line)).…”

Tuning direct current streaming dielectrophoresis of proteins

“…64). Assuming that l eo found previously for PDMS/glass channels 62 is in the same order of magnitude (10 À8 m 2 /Vs) as l ep for proteins, 65 two scenarios are possible. First, the protein has a positive charge; as a consequence EOF and electrophoresis act in the same direction.…”