Dr Jean-Luc Brousseau from the separations systems team at Malvern Instruments has recorded a downloadable presentation that helps illustrate the importance of specific analytical details when characterizing protein or polymer solutions. In "On the overlooked second virial coefficient" he explains the reasons why and how protein and polymer scientists can improve characterization results by measuring the 2nd virial coefficient, using either static light scattering or gel permeation chromatography/size exclusion chromatography (GPC/SEC). Improved results can then be used to optimize solubility and stability in a final product. This insightful and easy to follow presentation is freely available for download at: http://www.malvern.com/secondvirialcoefficient  

The second virial coefficient (A2) accounts for molecule-to-molecule interactions and is required for accuracy when measuring concentrated solutions of macromolecules. Closely correlated with sample solubility, a positive 2nd virial coefficient (A2) result suggests an easily solvated sample, whereas a negative result indicates a preference for molecule-molecule contact. The A2 parameter can therefore reveal details about the quality of the solvent and provide insight into stability and coating behaviours of polymers, or stability and crystallization behaviours in proteins. 

Dependent on pH, temperature and other parameters, A2 can be measured using static light scattering in batch or flow using GPC/SEC. Systems from Malvern Instruments' Zetasizer light scattering range and Viscotek GPC/SEC range, are therefore well suited to measuring A2 in either protein or polymer samples. The new presentation is the latest addition to a comprehensive applications library that can be found at: www.malvern.com