Cynthia N. Oliver

Using empirical phase diagrams to understand the role of intramolecular dynamics in immunoglobulin G stability

Understanding the relationship between protein dynamics and stability is of paramount importance to the fields of biology and pharmaceutics. Clarifying this relationship is complicated by the large amount of experimental data that must be generated and analyzed if motions that exist over the wide range of timescales are to be included. To address this issue, we propose an approach that utilizes a multidimensional vector-based empirical phase diagram (EPD) to analyze a set of dynamic results acquired across a temperature-pH perturbation plane. This approach is applied to a humanized immunoglobulin G1 (IgG1), a protein of major biological and pharmaceutical importance whose dynamic nature is linked to its multiple biological roles. Static and dynamic measurements are used to characterize the IgG and to construct both static and dynamic EPDs. Between pH 5 and 8, a single, pH-dependent transition is observed that corresponds to thermal unfolding of the IgG. Under more acidic conditions, evidence exists for the formation of a more compact, aggregation resistant state of the immunoglobulin, known as A-form. The dynamics-based EPD presents a considerably more detailed pattern of apparent phase transitions over the temperature-pH plane. The utility and potential applications of this approach are discussed.

Reversed-phase high-performance liquid chromatography of virus-like particles

A quantitative reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed to detect the L1 subunit protein from virus-like particles (VLPs) of human papillomavirus (HPV). The method utilizes heat treatment with a buffer consisting of 50 mM Tris, pH 8.0 containing 8 M guanidine-HCl and 10% 2-mercaptoethanol to dissociate the VLPs into monomeric L1. Following dissociation, the sample is injected onto a C4 or C8 column. The L1 protein is eluted as a single, clearly resolved peak. Elution conditions have been optimized to enhance the separation of L1 from other contaminants. Based on spike recovery studies and sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis this method is suitable for quantitation of various partially purified in-process samples and can be used to facilitate purification process development.