Studies On The Interactions Between Drugs And Proteins In Physiological Solution By Spectral Methods

The reaction mechanism of small molecules with protein was studied by fluorescence Spectroscopy (FS) and UV Spectroscopy (UV) and circular dichroism (CD) spectrum. Those reactions quenched the fluorescence produced.Chapter one reviews the molecular spectrum for the reaction of medicine and protein and metal ions and the progress of fluorescence Spectroscopy in pharmaceutical analysis in recent years; The results and methods for study of reaction mechanism between small molecules with protein, 54 documents are quoted.Chapter two.The binding reactions of lomefloxacin-copper(II) complex (LMF-Cu) or LMF to bovine serum albumin (BSA) in physiological solution were investigated by multi-Spectroscopy. The binding constant, the number of binding sites and the binding distance between LMF-Cu or LMF and BSA were obtained by a fluorescence quenching method and according to the mechanism of Forster-type dipole-dipole non-radioactive energy transfer, respectively. Enthalpy and entropy changes for two systems were calculated to be-7.970 kJ mol^-1 and 47.438 J mol^-1 K^-1 for LMF-BSA,-12.469 kJ mol^-1 and 33.542 J mol^-1 K^-1 for LMF-Cu-BSA, respectively. The highly positive values observed for the entropy give evidence for a strong interaction. The values of AH and AS in two systems are similar, indicating that electrostatic interactions in two systems play major role.The effect of LMF-Cu or LMF on the conformation of BSA was also analyzed by synchronous fluorescence, three-dimensional fluorescence and circular dichroismspectra. The results showed that the presence of Cu ion in LMF-Cu can affect the conformation of BSA to some degree. All theresults revealed that the addition of copper ion promotes the interaction of lomefloxacin with bovine serum albumin.Chapter three:The interaction and thermodynamic characteristics of the ternary complex about human serum albumin-lomefloxacin-copper (II) system in physiological medium were investigated by multi-spectroscopy. The experimental results showed that LMF or LMF-Cu²⁺ can quench the fluorescence of HSA with a static quenching mechanism, indicating that HSA react with LMF or LMF-Cu²⁺. The apparent binding constant / number of binding sites were estimated as 4.924×105 L mol^-1/ 1.473 for HSA-LMF, 8.990×10⁴ L mol^-1/ 1.785 for HSA-LMF-Cu²⁺, 1.100×10⁵ L mol^-1/1.212 for LMF-Cu²⁺ and 3.379×10² L mol^-1 /0.726 for HSA-Cu²⁺, respectively. AH and AS for LMF-HSA system were calculated to be -2.189 kJ mol^-1 and 61.25 J mol^-1 K^-1, which indicated that electrostatic interactions plays a major role in the interaction; whileâ–³H andâ–³S for HSA-LMF-Cu²⁺ system were -7.401 kJ moL^-1 and 47.63 J mol^-1 K^-1, which indicated that electrostatic interaction is also a major action in the interaction. According to Forster theory, the distance were gave as 5.006 nm for HSA-LMF and 4.709 nm for HSA-LMF-Cu²⁺. Synchronous fluorescence spectra and circular dichroism of HSA in presence of lomefloxacin indicated that the conformations of human serum albumin have been changed.Chapter four: Fluorescence Spectroscopy in combination with circular dichroism and UV-Vis absorbance spectrum were employed to investigate the binding of thionine - bovine serum albumin system in physiological conditions. The experimental results showed that electrostatic interaction plays a major role in the interaction, thionine can quench the fluorescence of BSA with a static quenching mechanism. Synchronous fluorescence Spectroscopy and circular dichroism of BSA in presence of thionine indicated that the conformations of bovine serum albumin have been changed.