Photometric Method Study On The Reaction Mechanism Of Small Organic Molecules With Proteins

This dissertation studies the reaction mechanism of some organic molecules, Alizarin red, acidic phenolsulfonphthaleins, Aesculin and Aesculetin with protein. Those reaction accord with Langmuir equation, quenched the fluorescence produced,at the same time content of Aesculin in cortex was directly mensurated , which did not separate by TLC. The detail as following Chapter one: The results and methods for study of reaction mechanism between small organic molecules with protein were reviewed with 55 references. Chapter two: The microphase absorption—spectral correction (MPASC) technique is described and applied to the study of the interaction of Alizarin red (ARS) with two proteins : bovine serum albumin (BSA) and human serum albumin (HSA) at pH 4.3 Britton―Robinson buffer solution . The results show that the absorption ratios of ARS to proteins are N_ARS-BSA = 9∶1,N_ARS-HAS = 7∶1,the absorption constants are K_ARS-BSA = 3.346×10⁴,K_ARS-HAS = 4.483×10⁴ respectively and the real molar absorptivities are measured to be ε_BSA-ARS(537 nm) = 2.517×10⁴ L·mol^-1·cm^-1,ε_HSA-ARS(519 nm) = 2.051 ×10⁴ L·mol^-1 ·cm^-1 . The detection limits are 19 mg·L^-1 for BSA , and 23 mg·L^-1 for HSA.The aggregation of ARS in protein has been applied to the analysis of samples with satisfactory results. Chapter three: The reactions between HSA and acidic phenolsulfonphthaleins including phenol red, cresol red, chlorophenl red, bromocresol purple and m-cresol purple have been investigated by the means of fluorescence. The experiments showed that all of the selected acidic phenolsulfonphthaleins strongly quenched the fluorescence produced by HSA, and this fluorescence quenching could be interpreted in terms of statistic quenching. From the calculation results of binding constants K for these dyes at various temperatures, it could be found that the increase in the functional groups numbers of dyes molecules resulted in an increase in K, while the increase in reaction temperature led to a decrease in K. The interactions between dyes and HSA were attributed to static-electricity gravitation which was confirmed by the calculation results of enthalpy and entropy for these reactions. According to...