The interaction of monoclonal antibodies (mAbs) with lectin concanavalin A (ConA) in solution and the conditions under which protein binding occurs optimally were studied. By measuring the intrinsic fluorescence of tryptophan, we investigated the unfolding of the structural conformation of the mAb while changing parameters such as pH of the buffer, incubation temperature, and length of incubation time. Based on these measurements, a melting temperature (Tm) of 61 ° C and a denaturation time (tm) of approximately 60 minutes were determined. The formation of aggregates and the formation of a possible bond between mAb and ConA were investigated using the size exclusion chromatography method. No protein binding was detected. In order to completely expose the glycosidic residues on the mAb structure, we added DTT. However the reduction of disulfide bonds and consequently cleavage of the mAb on light and heavy chains most likely did not take part. We concluded that, the cause of aggregate formation, with the concomitant loss of the native form, and the absence of cleavage of the mAb by the addition of DTT, could possibly be the result of oxidative effect of the latter on the mAb. The effects could be triggered by the elevated temperature of mAb incubation. The likely pre-oxidation and consequent inadequacy of the DTT reagent was also demonstrated by detecting it at 280 nm. We also tried binding dextran and glycosylated BSA with ConA. In no case did the binding take place. Exclusion chromatography revealed that ConA, independently of the environmental factors, exists in the monomeric form which is biologically inactive.
|
