Conjugated & Membrane Proteins

Membrane proteins solubilized with detergent are particularly difficult to analyze by traditional techniques or even by mass spectroscopy because of the surfactant micelle surrounding the protein. Denaturing SDS-PAGE dissociates native oligomers and precludes their identification, while cross-linked mass spectroscopy can create oligomers that do not exist in solution.

Likewise, heavily glycosylated proteins cannot be represented by reference standards or common models for globular proteins, and so are not amenable to analysis by traditional techniques.

These challenges are met by multi-angle light scattering coupled with SEC (SEC-MALS) which can distinguish between a protein and its associated detergent or carbohydrate by combining data from three detectors downstream of SEC separation: UV, MALS and differential refractive index (dRI). ASTRA's Conjugate Analysis algorithm calculates the molar masses of both the proteinaceous component and the conjugated or micellar component. The true oligomeric or complexated state of the protein, as well as the degree of glycosylation, are determined unambiguously.