ABSTRACT
HSA is the highly water-soluble plasma protein, which is the smallest and most abundant plasma protein in the human body. Oxazepam [O] and Flurazepam [F] include the most frequently prescribed sedative-hypnotic agents. [F] and [O] bind to human serum proteins more than 95%. Investigations show that HSA has an important role as a carrier for diazepins. The interaction of drugs with HSA, which may have important pharmacokinetics implications, has been extensively studied by several workers. The binding of two diazepins [Oxazepam [O] and Flurazepam [F]] to HSA was investigated by means of spectrophotometry. The binding isotherms for interaction of [F] and [O] with HSA at 25 °C shows the variation of v, the average of bound [O] and [F] per HSA molecule, versus log [D]. The corresponding Scatchard plots for these isotherms were driven. They coincide with usual shapes of Scatchard plots and can represent the existence of one binded set. The binding parameters, binding constant and binding capacity of these medicines were obtained from Hill equation. The binding constants of Flurazepam [F] and Oxazepam [O] were determined 0.6 +/- 0.1[xl0[5]] and 1.4 +/- 0.3 [xl0[5]] respectively. The binding capacity of [F] and [O] were computed 1 +/- 0.1 and 1.3 +/- 0.1, and the Hill constant [n[H]] was obtained 4.076 and 2.44 respectively. The results of this study show, spectrophotometry can be a simple and fast technique to determine the binding constant for some ligands.: These values show the binding affinity of [O]is more than [F], on the other hand, the cooperativity of [F]; is higher than [O]. With regards to the amount of K, binding affinity of [O] to HSA is more than [F]. These results can be justified by the amounts of partition coefficient of [O] and [F]
ABSTRACT
Surfactin, a crystalline peptide lipid surfactant produced by Bacillus subtilis, inhibits fibrin clot formation. Human Serum Albumin [HSA] is the most abundant protein in the circulatory system. Its principal function is to transport a great variety of metabolites and drugs such as anticoagulants. In the present work, the interaction of HAS with surfactin in solution as a function of concentration is reported. The structure of HSA at different pH values in the absence and presence of surfactin was investigated by fluorescence and circular dichroism [CD] spectroscopies. The different effects of surf actin upon binding to HSA are interpreted based on considerations of the expected changes in the vicinity of tryptophan residue W[214]. The results of fluorescence and CD showed that HSA partially unfolded at pH 3.0 and 10.0 in comparison with pH 7.0. At pH 7.0 and 10.0, surf actin at low concentrations caused a red shift of maximum emission and at high concentrations a blue shift of maximum emission, which should mean unfolding after partial folding. But, compare with other pH values [pH 7.0 and 10.0], in pH 3.0, surf actin does not have considerable effect. Stability of HSA obtained at pH 7.0 and 10.0. deltaG [H2O] was about 15 kJmol-1 at pH 7.0 and pH 10.0. Surfactin can denature HSA at very low concentration [0.01 mM]. This effect is very similar to synthetic anionic surfactants such as sodium dodecyl sulfate