arXiv subjects

D. Buzatu

Publications and source records attributed to D. Buzatu.

3 recordsLinked to original sources

arXiv2004

Conductivity and Viscosity Measurements for Binary Lysozyme Chloride Aqueous Solution and Ternary Lysozyme-Salt-Water Solution

We use the conductimetric method, adequate to electrolytes, to determine the lysozyme charge in lys-water and ternary lys-salt-water systems. We measured also the viscosities for the above binary and ternary systems in the same conditions at pH$=4.5$ and T$=298$ K, measurements that allow us to see any effect of viscosity on cations mobilities and implicitly on the lysozyme charge. The method is illustrated for the lysozyme chloride aqueous solution system at 25$^o$ C, using the data reported here for pH$=4.5$ at 0.15, 0.6, 0.8, 1., 1.5, 2., 2.5, 3., 3.5 mM (mg/mL) lysozyme chloride concentrations. The method was also applied to ternary lys-salt-water systems in the same conditions at pH$=4.5$ and T$=25^o$ C. Ternary conductivities are reported for a mean concentration 0.6 mM of lysozyme chloride in all systems and a mean concentration 0.01, 0.025, 0.05, 0.1, 0.175, 0.2, 0.5, 0.7, 0.9, 1.2, 1.3 and 1.4 M for NaCl; 0.005, 0.01, 0.05, 0.1, 0.175, 0.2, 0.5, 0.7, 0.9, 1.2, 1.3, 1.4 and 1.5 M for KCl; 0.005, 0.01, 0.05, 0.1, 0.175, 0.2, 0.5, 0.7, 1.2, 1.3, 1.4, 1.5, 1.6 and 1.7 M for NH$_4$Cl.

physics.chem-ph↗

arXiv2004

Measurements of Multicomponent Diffusion Coefficients for Lysozyme Chloride in Water and Aqueous Na$_2$SO$_4$

This paper presents a diffusion experimental study for ternary lysozyme-Na$_2$SO$_4$-water system, from moderate precipitant concentrations into the supersaturated region and provides a complete set of four diffusion coefficients. These data are important in order to provide accurate models of protein diffusion with applications in growth of protein crystals for X-ray diffraction studies. All three-component mutual-diffusion experiments reported here were performed by Rayleigh interferometry at pH$=4.5$, T$=25^o$ C and at a mean lysozyme concentration (average of top and bottom solution concentrations) of 0.6 mM (8.6 mg/mL). Four experiments, with different combinations of protein and Na$_2$SO$_4$ concentration differences, were performed at each of five mean Na$_2$SO$_4$ concentrations (0.1, 0.25, 0.5, 0.65 and 0.8 M), for a total of 20 experiments. In addition, we have measured dynamic light-scattering diffusion coefficients of the ternary system lysozyme chloride-Na$_2$SO$_4$-water.

physics.chem-ph↗

arXiv2004

Extraction of Thermodynamic Data from Ternary Diffusion Coefficients of Lysozyme Chloride in Water and Aqueous Na$_2$SO$_4$

This paper presents, for ternary lysozyme-Na$_2$SO$_4$-water system, the thermodynamic data extracted from the measured values of four ternary diffusion coefficients and the Onsager reciprocal relations. The calculation for derivatives of solute chemical potentials with respect to solute molar concentrations was made using the method presented in \cite{1}. This method is applicable to systems in which the molar concentration of one solute is very small compared to that of the other, like in our case. The approach is illustrated for the lysozyme chloride-Na$_2$SO$_4$-water system at 25$^o$ C, pH 4.5 and at 0.6 mM (8.6 mg/mL) lysozyme chloride and 0.1, 0.25, 0.5, 0.65, and 0.8 M Na$_2$SO$_4$ concentrations. The calculated solute chemical potential derivatives were used to compute the protein cation charge approximately. We also compute the diffusion Onsager coefficients $(L_{ij})_o$ for each composition at pH 4.5.

physics.chem-ph↗