The affinity process of cadmium ion and guanine ribonucleotide(GMP)was studied by isothermal titration calorimetry,focusing on the similarities and differences between different proportions of cadmium ion and GMP.The experimental results showed that:(1)the different concentration ratio of cadmium ion and GMP had a significant effect on the binding process,and the reaction was enthalpy driven exothermic reaction at low concentration ratio.At high concentration ratio,the reaction was endothermic.According to the ITC curve and OneSite model fitting results when the concentration ratio of cadmium ion to GMP was 20∶1,cadmium ion and GMP were close to the binding ratio of 1∶1,and the affinity K value was 1.21E 4±2.26E 3.(2)It was speculated that GMP and cadmium ion had two binding sites,one was exothermic binding site and the other was endothermic binding site.At low concentration ratio,only exothermic binding site occurred.When the concentration ratio reached a certain value,endothermic binding sites will be activated,and endothermic and exothermic binding will occur at the same time.Because the endothermic binding site was more powerful,the reaction may become endothermic.(3)Through the comparison of the reverse drop method and the positive drop method,under the same concentration,different drop adding methods will also have a greater impact on the combined results.The method adopted in this study can well analyze the affinity mechanism of metal cadmium ion and GMP from the macroscopic thermodynamic point of view,and the research results provided an important experimental basis and theoretical guidance for the screening of functional monomers in the subsequent preparation of cadmium ion imprinting.
维普
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