SINGLE-STEP PURIFICATION OF A BACTERIALLY EXPRESSED ANTIBODY F-V FRAGMENT BY IMMOBILIZED METAL AFFINITY-CHROMATOGRAPHY IN THE PRESENCE OF BETAINE

A procedure was developed for the rapid isolation of an antibody F-v f ragment expressed in Escherichia coil via immobilized metal affinity c hromatography. Metal affinity was mediated by fusing hexahistidine tai ls to both the V-L and the V-H domain and was thus independent of the antigen-binding specificity. Unexpectedly, it was not possible to isol ate the F-V fragment with correct stoichiometric composition of the tw o variable domains under standard chromatographic conditions. Proper n on-covalent association of V-L and V-H was, however, maintained when u sing glycine betaine as electrolyte, thus permitting purification of t he intact F-v fragment to homogeneity in a single step.