Preparation Of Realgar Nanoparticle And The Studies On Its Interaction With BSA Spectroscopic Studies On The Interaction Between Nicotine And BSA

PartⅠRealgar nanoparticle was prepared with mineral realger which was dissolved with NaOHor Na2S under the sealed condition and then precipitated by diluted hydrochloric acid. Realgarnanoparticles of 10nm diameter or so were obtained under the different surfactants whentemperature and pH were controlled . Studies implied that macromolecule polymer surfactants cankeep the realgar nanoparticles much more stable than the nonionic surfactants and then theanionic surfactants which followed by cationic surfactants. Temperature have to be kept low andpH were controlled between 3-6. Components of realgar nanoparticle were also determined byEDS and XPS. UV/vis spectra, fluorescence spectra and resonance scattering spectra were also employed tostudy the binding between realgar nanoparticle and BSA under different temperatures and pHs.UV spectro-scopy tracking experiment suggested the hysteretic effect exist in binding between 2广西师范大学硕士论文:血清白蛋白生物无机化学相关研究realgar nanoparticles and BSA which due to first order reaction both at pH7.4 and pH4.7.Fluorescence quenching spectra between realgar nanoparticles and BSA indicated static quenchingexist both at pH7.4 and pH4.7 and the quenching constant is more noticeable at pH7.4 than atpH4.7 while the binding constant was converse. Resonance scattering spectra revealed theencapsulating ratio of BSA]/[realgar nanoparticle] is three times at pH 4.7 as much as at pH7.4 .All the evidence showed it is all related with BSA coformations in different pHs. Thermodynamicparameters(?H?,?G?,?S?) of the combination of realgar nanoparticle and BSA were also givenwhich are: ?H?<0, ?G?>0 and ?S?<0.It concluded that the combination between BSA andrealgar nanoparticle is exothermal reaction and the realgar nanoparticle which bear withenormous surface energy overcomed the energy barrier of the hysteretic effect between BSA andnanoparticle through releasing stability energy after being encapsulated by BSA and the enormousconformational entropy was losed when BSA was absorbed to the surface of realgar nanoparticlewith specific conformation.Part Ⅱ Interaction between nicotine and BSA(i.e. bovine serum albumin) was investigated byfluorescence spectra and UV/vis spectra . The fluorescence spectra showed that BSA fluorescencequenched regularly with the addition of nicotine. The fluorescence quenching mechanism werealso studied in pH5.0,pH7.4 and pH11.0 by Stern-Volmer equation , indicating dynamicquenching(pH5.0) and static quenching(pH7.4 and pH11.0) respectively. Association constants(k)of nicotine and BSA in pH7.4 and pH11.0 in the temperatures of 20℃ and 37℃ were given byLineweaver-Buck equation, which are: k20℃=140.15L.mol-1, k37℃=131.83 L.mol-1(pH7.4) andk20℃= 141.76 L.mol-1 , k37℃=27.79L.mol-1 ( pH11.0), suggesting the association constant iseffected by temperature much more remarkably in pH7.4 than in pH11.0 because of the differentstates of nicotine in different pHs. The UV/vis exhibited the absorbance of BSA(210nm) to shift tored and decrease gradually with the addition of nicotine, reflecting the transition of secondarystructure of BSA, namely the helix of BSA become looser. UV/vis second derivative spectra andsynchronous spectra (?λ= λem-λex=15nm and ?λ= λem-λex =60nm) implied the change of themicrocircustance of aromatic amino residue of BSA(Trp, Tyr and Phe) from hydrophobicity tohydrophilicity in high concentration of nicotine.