SPECTROFLUOROMETRIC STUDY OF THE PH EFFEC T ON THE COMPLEXATION OF CINCHONINE WITH BETA-LACTOGLOBULIN (BETA-LG)

pH effect on complex formation between beta-LG and cinchonine is studi ed by fluorescence spectroscopy in aqueous buffer solutions in the 5.8 5 - 8.2 pH range, where cinchonine is essentially a monocation. Specif ic interactions were observed with very close affinity constant values (between 17.10(3) and 23 x 10(3) M-1), throughout the investigated pH , except pH 8.2 where no significant complexation was noted. The latte r phenomenon may be due to a reversible structural evolution of the pr otein occurring at pH > 7.5.