Protein binding of a series of rifamycins to bovine serum albumin as measured by the "two-phase partition" technique.

A "two-phase partition technique" was developed and improved so as to be useful for the study of the interaction of proteins with low-molecular-weight ligands. The technique permits the macromolecule to be present almost entirely in one of the two aqueous phases without the aid of any physical solid interface, which is particularly useful in studies of lipophilic ligands. Compared with the other two-phase systems set up for binding studies, that used in this work takes advantage of the use of a more suitable medium, which permits a better protein partition even at very low ionic strengths. As an example of its usefulness the measurement of the binding parameters of a series of rifamycins to bovine serum albumin is reported.