No abstract

The pharmacokinetics and pharmacodynamics of any drug will depend, largely, on the interaction that it has with human serum albumin (HSA), the most abundant plasma protein. The interaction between newly synthesized Pd(II) complexes, 2,2'-bipyridin octyl dithiocarbamato Pd(II) nitrate (Octpd), 2,2'-bipyridin butyl dithiocarbamato Pd(II) nitrate (ButPd), 2,2'-bipyridin ethyl dithiocarbamato Pd(II) nitrate (EtPd), antitumor components, with human serum albumin, a carrier protein, were studied at different temperatures of 27 and 37 degrees C by fluorescence spectroscopy, far UV circular dichroism (CD), and spectrophotometric and differential scanning calorimetry (DSC) techniques. By the analysis of fluorescence intensity, it was observed that Pd(II) complexes have strong abilities to quench the intrinsic fluorescence of HSA through a dynamic quenching procedure. The binding parameters were evaluated by the fluorescence quenching method. The thermodynamic parameters, including DeltaH degrees , DeltaS degrees , and DeltaG degrees , were calculated by the fluorescence quenching method and indicated that hydrophobic forces play a major role in the interaction of Pd(II) complexes with HSA. Far-UV-CD results represented that Pd(II) complexes induced a decrease in content of the alpha helical structure of protein. The binding of newly designed drugs (Pd(II) complexes) on the blood carrier protein of HSA resulted in significant alterations on the structure and conformation of protein via decreasing stability of HSA by decreasing the T(m), a red shift in maximum fluorescence intensity, a decrease in content of the alpha-helical structure, and the increase of the nonpolar or accessible hydrophobic surface of HSA to solvent.

The binding of curcumin (CUR) and diacetylcurcumin (DAC) to bovine beta-lactoglobulin (BLG) genetic variant B was investigated by fluorescence and circular dichroism techniques. The binding parameters including number of substantive binding sites and the binding constants have been evaluated by fluorescence quenching method. The distance (r) between donor (BLG) and acceptor (CUR and DAC) was obtained according to the Förster's theory of non-radiative energy transfer. The far-UV circular dichroism spectra were used to investigate the possible changes in the secondary structure of BLG in the presence of CUR and DAC and showed that these two ligands change the alpha-helix and random coil contents of this protein to some extent. The visible circular dichroism spectra indicated that the optical activity during the ligand binding was observed due to the induced-protein chirality. All of the achieved results suggested the important role of the phenolic OH group of CUR in the binding process resulted in more affinity of CUR than DAC for binding to BLG.