Serum Albumin With Drug Molecules Interact By Fluorescence

Serum albumin is the most abundant protein in plasma. It can bind with many intrinsic and extrinsic materials, and transfer them to various parts of the body. Therefore, the study of the interaction between serum albumin and drugs is a very important task inthe fields of life science and chemistry.Ofloxacin(OFLX) is a quinolone antibiotics. It has been extensively used in the clinic medicine. In this dissertation, fluorescence spectra of OFLX in near neutral conditions have been studied first, and using quinine bisulphate as a reference, fluorescence quantum yield of OFLX was measured to be 0.175. Based on this study, interaction between OFLX and bovine serum albumin (BSA) was studied. The results show that the fluorescence quenching effect of OFLX on BSA is because of a static energy transfer mechanism. The number of binding sites between OFLX and BSA was deduced to be 1, and the association constant at room temperature was determined to be K = 4.0 X 103 (mol/L)-1. Based on the Forster non-irradiation resonance energy transfer theory, the distance between OFLX and 212-trypyophane residue of BSA was calculated to be 3.69 nm. According to the thermodynamic parameters of the interaction, the main binding force between OFLX and BSA was considered to be Van der Waals force. Using the same method, interaction between OFLX and human serum albumin (HSA) has also been studied.Quinine is an early used drug to resist malaria, it is also an extensively used fluorescence reagent in analytical chemistry, biochemistry and medical science. But its detailed study of fluorescence spectra has not been found in the literature. In the work, fluorescence spectra and ultraviolet spectra of quinine were deeply studied. It was found that quinine existed in four fluorescence forms in different acidic and basic conditions, and produced different fluorescence spectra. In strong acidic conditions, namely pH<3.0, quinine mainly exists in H3L2+ form, the maximum excitation and the maximum emission wavelengths are 345 nm and 452 nm respectively. In weak acidic conditions and near neutral conditions, quinine mainly exists in H2L+ and HL forms, the maximum excitation and the maximum emission wavelengths are 331 nm and 384 nm respectively. In weak basic conditions, the maximum emission wavelength shifts to 382 nm, and the fluorescence intensity gradually descends, In strong basic conditions, quinine mainly exists in L' form, which has weak fluorescence. The interaction between quinine and BSA in different conditions has also been studied by fluorescence method, but unfortunately, no obvious evidence of fluorescence spectra was found to interpret t the interaction between quinine and BSA.