Measurement Of Second Virial Coefficients Research Articles

The accurate measurement of second virial coefficients using self-interaction chromatography: Experimental considerations

Measurement of B22, the second virial coefficient, is an important technique for describing the solution behaviour of proteins, especially as it relates to precipitation, aggregation and crystallisation phenomena. This paper describes the best practise for calculating B22 values from self-interaction chromatograms (SIC) for aqueous protein solutions. Detailed analysis of SIC peak shapes for lysozyme shows that non-Gaussian peaks are commonly encountered for SIC, with typical peak asymmetries of 10%. This asymmetry reflects a non-linear chromatographic retention process, in this case heterogeneity of the protein–protein interactions. Therefore, it is important to use the centre of mass calculations for determining accurate retention volumes and thus B22 values. Empirical peak maximum chromatogram analysis, often reported in the literature, can result in errors of up to 50% in B22 values. A methodology is reported here for determining both the mean and the variance in B22 from SIC experiments, includes a correction for normal longitudinal peak broadening. The variance in B22 due to chemical effects is quantified statistically and is a measure of the heterogeneity of protein–protein interactions in solution. In the case of lysozyme, a wide range of B22 values are measured which can vary significantly from the average B22 values.

Self-interaction chromatography of proteins on a microfluidic monolith

A novel miniaturized system has been developed for measuring protein–protein interactions in solution with high efficiency and speed, and minimal use of protein. A chromatographic monolith synthesized in a capillary is used in the method to make interaction measurements by self-interaction chromatography (SIC) in a manner that, compared to column methods, is more efficient as well as more readily practicable even if only small amounts of protein are available. The microfluidic monolith requires much less protein for both column preparation and the chromatographic measurements than a conventional SIC system, and in addition offers improved mass transfer and hence higher chromatographic efficiency than for previous SIC miniaturization systems. Protein self-interactions for catalase as a model protein, quantified by measurement of second virial coefficients, B22, were determined by SIC and follow trends that are consistent with previously reported values. Different column derivatization conditions were studied in order to optimize the chromatographic behavior of the microfluidic system for SIC measurements. Chromatographic sensitivity can be further increased by using different column synthesis conditions.

Rotational excitation of NH3 and ND3 due to He atom collisions

Quantum close-coupling and coupled-states approximation scattering calculations for rotational energy transfer of rotationally excited NH3 and ND3 due to collisions with He are presented. Calculations were performed for collision energies between 10-5 and 10 000 cm-1 using the NH3-He potential of Hodges and Wheatley [J. Chem. Phys. 114, 8836 (2001)]. State-to-state and total quenching cross sections from some selected initial states are presented. Rate coefficients for ortho-NH3 for the quenching 10+→00+ transition were obtained on potentials scaled to reproduce measurements of second virial coefficients with the results showing strong sensitivity to the potential, especially at low temperatures. Significant isotope effects are found in quenching cross sections in the cold to ultracold regime particularly in the region dominated by quasi-bound resonances, ~0.1 to 10 cm-1. As ammonia has been translationally cooled via Stark deceleration methods, it is a good candidate for experimental study of such effects at cold temperatures. Comparison of rate coefficients with available theoretical results are also presented.

A simpler analysis for the measurement of second virial coefficients by self-interaction chromatography

We describe a thermodynamic approach that supports the adoption of a simplified procedure for the determination of protein second virial coefficients (B2) by self-interaction chromatography. Its major advantage over the original method is a decrease in the number of parameters to which magnitudes must be assigned for the determination of B2. Improved correlation of virial coefficients obtained by the chromatographic procedure with those obtained by light scattering is achieved by taking into account the twofold larger magnitudes of the former because of the experimental distinction between free and immobilized protein molecules in self-interaction chromatography.

Second virial coefficients of fluorinated methanes CH4−xFx(x = 0–4) and their binary mixtures

Download options Please wait... Supplementary files Tables DOC (922K) Article information DOI https://doi.org/10.1039/B204839F Article type Paper Submitted 17 May 2002 Accepted 16 Jul 2002 First published 12 Aug 2002 Download Citation Phys. Chem. Chem. Phys., 2002,4, 4444-4448 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Second virial coefficients of fluorinated methanes CH4−xFx (x = 0–4) and their binary mixtures J. A. Lamp, B. F. Schramm, S. M. Saad and S. A. El-Geubeily, Phys. Chem. Chem. Phys., 2002, 4, 4444 DOI: 10.1039/B204839F To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Joachim A. Lamp Bernhard F. Schramm Shokry M. Saad Samia A. El-Geubeily

Measurements of the Second Virial Coefficients of Some New Chlorofluorocarbons and of Their Binary Mixtures at Temperatures in the Range from 296 K to 475 K

AbstractWe present measurements of second virial coefficients of the chlorofluorocarbons R12 (CCl2F2), R22 (CHCIF2), R114 (CClF2—CClF2), R134a (CH2F—CF3), R142b (CH3—CClF2), R152a (CH3—CHF2) and of the binary mixtures R12/R22, R22/R114, R22/R142b, R22/R152a, and R134a/R152a in the temperature range from 296 K to 475 K. The data are combined with earlier measurements of the same systems at low temperatures (J. Chem. Thermodyn. 23, 281 (1991)) for a critical discussion on the basis of the Stockmayer intermolecular potential model.

Precise Measurements of Second Virial Coefficients of Simple Gases and Gas Mixtures in the Temperature Range Below 300 K

AbstractA new apparatus for measurements of second virial coefficients of gases or gas mixtures at room temperature is described. It was used to determine virial coefficients of He, H2, N2, CO2, NH3, and the interaction virial coefficient of Ar/NH3. Furthermore, low temperature interaction virial coefficients of Ar/NH3and H2/CO are reported and finally a critical revision of second virial coefficients of He, H2, Ar, N2, and CO at 77.3 K is presented. The virial coefficients are discussed in their relation to new intermolecular potentials.

Measurements of the second virial coefficients of some new chlorofluorocarbons and of their mixtures at temperatures in the range from 230 K to 300 K

We present measurements of second virial coefficients of the chlorofluorocarbons R114, R123, R142b, R152a, and of their mixtures with R22, in the temperature range from 300 K down to their normal boiling temperatures. In order to clarify some discrepancies with high-temperature values from the literature we discuss our results on the bases of the theorem of corresponding states and of the Stockmayer potential.

Second virial coefficients and intermolecular forces in the system C Cl 2F 2/CHClF 2

Measurements of second virial coefficients of freons R12(C Cl 2F 2) and R22 (CHClF 2) and their mixtures in the temperature range between 223 and 300 K are reported. From the virial coefficients Stockmayer potential parameters were determined that describe the data in the whole temperature range and fit viscosity data simultaneously.

Messungen des zweiten Virialkoeffizienten von Gasen und Gasmischungen bei Zimmertemperatur mit einer Expansionsapparatur

AbstractWe describe an expansion apparatus for measurements of second virial coefficients of pure gases and mixtures at room temperature. We present experimental data of CO, CO2, Xe, CH4, CF4 and of the binary mixtures Ne/Xe, Ar/N2, Ar/CO, Ar/CO2, and CH4/CF4.

Second virial coefficients of nitrogen at very low temperatures

Measurements of second virial coefficients of nitrogen at temperatures 77.3, 87.2 and 90.1 K are presented. The results agree well with recently published data by Pocock and Wormald.