Studies On The Interactions Between PNP, SuDanⅢ And Bovine Serum Albumin By Spectroscopic Methods

Serum albumin is the most abundant protein in blood plasma, and the basic oflife which can bind with intrinsic and extrinsic small molecule substances, and as thecarrier protein, it can storage, transport and metabolism. By studying the interactionmechanism among serum albumin, small drug molecules, small organic moleculesdeeply, it can provide a wealth of information to systematic understand the structureof drugs and biochemistry, clinical medicine and pharmacokinetics, the result ishelpful to understand the drugs and small molecules absorption, distribution andexcretion, it has important reference value to study drug pharmacology and toxicity,and has important significance to further understanding the structure of the carrierprotein and develop new medicine better.Experiments has investigated the interaction mechanism between BSA and thetwo small molecule substances （PNP, SDⅢ） by several spectroscopic techniques, atthe same time also has studied the zone of action, binding sites and actionmechanism.The main results are as follows:Firstly, the interaction of PNP with BSA have been studied by fluorescencequenching technique in combination with UV-vis absorption, fourier transforminfrared （FT-IR）, circular dichroism （CD） spectroscopies and3D fluorecencespectroscopy under the simulative physiological conditions. The results showed thatthe quenching of BSA fluorescence by PNP was found to be a static quenchingprocess. Based on the experiments, the binding constants （Ka） were calculated to be3.310,2.375and2.153L·mol^-1at291,299, and307K, respectively. All of thebinding sites about1. According to the van’t Hoff equation, the thermodynamicparameters were estimated, which indicated that PNP interacted with BSA mainlythrough hydrogen bonds and Van der Waals interactions, and accompanied by weakelectrostatic interactions. The entropy reduce and the free energy recucing in thiscombining process proved it is a spontaneous procedure. The binding distance between BSA and PNP was calculated to be1.58nm according to the theory ofF rster. The displacement experiments pointed out that PNP could bind to the Site Iof BSA. Alteration of the protein structure in the presence of the PNP was confirmedby CD, FT-IR,3D fluorecence spectroscopy.Secondly, the interaction of SDⅢ with BSA have been studied by fluorescencequenching technique in combination with UV-vis absorption, fourier transforminfrared （FT-IR）, circular dichroism （CD） spectroscopies and3D fluorecencespectroscopy under the simulative physiological conditions. The results showed thatthe quenching of BSA fluorescence by SDⅢ was found to be a mainly staticquenching, accompanied dynamic quenching procedure. Based on the experiments,the binding constants （Ka） were calculated to be5.650×10³,2.240×10⁵and5.380×10⁵L·mol^-1at291,299, and307K, respectively. All of the binding sites about1.According to the van’t Hoff equation, the thermodynamic parameters were estimated,which indicated that SD Ⅲ interacted with BSA mainly through hydrophobicinteractions, and accompanied by weak electrostatic interactions. The entropyincrease and the free energy recucing in this combining process proved it is aspontaneous procedure. The binding distance between BSA and SDⅢ was calculatedto be1.50nm according to the theory of F rster. The displacement experimentspointed out that SDⅢ could bind to the Site I of BSA. Alteration of the secondaryprotein structure in the presence of the SDⅢ was confirmed by CD, FT-IR,3Dfluorecence spectroscopy.