Study On The Interactions Of Drug To Proteins And DNA

The interactions of silymarin with bovine serum albumin （BSA） and lysozyme（LYS） were investigated in physiological buffer （pH=7.4） by fluorescence spectroscopyand UV-vis absorption spectroscopy. The mechanism study indicated that silymarincould strongly quench the intrinsic fluorescence of BSA （LYS） through static quenchingprocedures. At291K, the values of the binding constant KAwere4.20×10⁴and4.71×10⁴L mol1for silymarin-BSA and silymarin-LYS, respectively. Usingthermodynamic equations, the conclusion that hydrophobic and electrostatic forcesplayed an important role in stabilizing complex of silymarin-BSA or silymarin-LYS wasobtained. The effects of Cu²⁺, Mg²⁺, Ca²⁺, Fe²⁺and Fe³⁺on the binding were also studiedat291K. The distances r0between donor and acceptor were calculated to be3.36and2.71nm for silymarin-BSA and silymarin-LYS, respectively. Synchronous fluorescencespectra showed that the conformation of BSA and LYS were changed by silymarin.Clenbuterol interacting with bovine serum albumin （BSA） or lysozyme （LYS） inphysiological buffer （pH7.4） was investigated by the fluorescence spectroscopy andUV–vis absorption spectroscopy. The results indicated that clenbuterol quenched theintrinsic fluorescence of BSA and LYS via a static quenching procedure. The bindingconstants of clenbuterol with BSA and LYS decreased with increasing temperature. Thevalues of ΔH and ΔS implied that hydrophobic and electrostatic interaction played amajor role in stabilizing the complex of clenbuterol-BSA and clenbuterol-LYS. In thepresence of Fe²⁺, Fe³⁺, Cu²⁺, Mg²⁺, Ca²⁺, or Zn²⁺, the binding constants of clenbuterol toBSA or LYS had no significant differences. The distances between the donor （BSA orLYS） and acceptor （clenbuterol） were2.61and2.19nm for clenbuterol-BSA andclenbuterol-LYS respectively. Furthermore, synchronous fluorescence spectrometry was used to analyze the conformational changes of BSA and LYS.THPP interacting with BSA or LYS was investigated by the fluorescencespectroscopy and UV-vis absorption spectroscopy. The results indicated that THPPquenched the intrinsic fluorescence of BSA and LYS via a dynamic quenchingprocedure. KAand n were obtained with increasing temperature. In the presence of Fe²⁺,Fe³⁺, Cu²⁺, Mg²⁺, Ca²⁺, or Zn²⁺metal ions, the binding constants of THPP to BSA orLYS had no significant differences. The distances between the donor and acceptor werecaculated for THPP-BSA and THPP-LYS.Salbutamol interacting with deoxyribonucleic acid （DNA） was examined byfluorescence, UV absorption, viscosity measurements, and DNA melting techniques.The binding constants KAand binding sites n were obtained at different temperatures byfluorescence quenching. The Stern-Volmer plots showed that the quenching offluorescence of salbutamol by DNA was a static quenching. To probe the binding mode,various analytical methods were performed and the results were as follows:hyperchromic effect was shown in the absorption spectra of salbutamol upon addition ofDNA; There was no appreciable increase in melting temperature of DNA whensalbutamol was presented in DNA solution; the fluorescence intensity ofsalbutamol–DNA decrease with the increasing ionic strength; the relative viscosity ofDNA did not change in the presence of salbutamol; the binding constant of salbutamolwith double strand DNA （dsDNA） was much higher than that of it with single strandDNA （ssDNA）. All these results indicated that the binding mode of salbutamol to DNAshould be groove binding. The thermodynamic parameters suggested that hydrogenbond or van der Waals force might play an important role in salbutamol binding toDNA. The binding distance between the acceptor and donor was3.70nm.