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A novel insulin-disubstituted Co(Ⅲ)protoporphyrin IX,CoPI,where I is insulin and CoP is Co(Ⅲ)protopor-phyrin IX,was prepared by covalently coupling the propionate groups on the porphyrin ring to the ε-amino groupsof B29-Lys on insulin via amide linkages.The FTIR spectra in the amide I region(1600—1700 cm~(-1))and circulardichroism study show that CoPI has a conformation similar to the insulin at pH 6.9,whereas it exhibits significantconformational changes in structure as compared with the insulin self at pH 8.2.The pH absorption titration indi-cates that the alkaline conditions(pH≥8.0)are required for the formation of complexes between the free CoP andthe insulin.The thermodynamic and kinetic data reveal that free CoP is bound to either the zinc-insulin or free insu-lin with a dissociation constant of(2.0±0.3)×10~(-5)or(2.2±0.3)×10~(-5)mol/L. 相似文献
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反相-高效液相色谱手性流动相添加剂法测定酸奶及含乳饮料中乳酸对映异构体 总被引:1,自引:0,他引:1
选取2,3,6-三甲基-β-环糊精(TM-β-CD)作为流动相手性添加剂,建立了采用反相高效液相色谱法分离酸奶及含乳饮料中乳酸异构体的方法。实验采用hypersil ODS2-C18(250×5.0mm,5μm)色谱柱,以0.5mmol/L PH2.5的TM-β-CD(含4.5mmol/L H2SO4)作为流动相,流速为1.0mL/min,紫外检测波长为210nm。实验考察了不同色谱柱、柱平衡时间、手性流动相添加剂浓度及pH值对分离效果的影响,并进一步研究了方法的线性范围、检出限、精密度及回收率。 相似文献
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