ABSTRACT
When a detergent which preserves the activity of the protein has been found, chromatographic procedures have to be used to prepare a homogeneous solution. Solubilization of the protein with a detergent is necessary in order to prepare an aqueous solution of a single type of oligomer, as membrane proteins in the absence of detergents would form aggregates. When searching for a new detergent, it has to be taken into consideration that detergents usually bind to proteins by hydrophobic interaction, as the half-saturation concentration of detergent-to-protein binding is generally close to the CMC of the detergent. Microdialysis has the advantage of keeping the concentration of detergent and salt in the protein solution constant when increasing the concentration of the precipitating agent. A protein-detergent micelle might be considered in a rough approximation as a polymer molecule. Indeed, phase separation and crystallization of membrane proteins in Polyethylene glycol (PEG) solutions has similarities with the dextran-PEG system.
