Multimerization and Aggregation of Native-State Insulin: Effect of Zinc

详细信息    查看全文

• 作者：Yisheng Xu ; Yunfeng Yan ; Daniel Seeman ; Lianhong Sun ; Paul L. Dubin
• 刊名：Langmuir
• 出版年：2012
• 出版时间：January 10, 2012
• 年：2012
• 卷：28
• 期：1
• 页码：579-586
• 全文大小：911K
• 年卷期：v.28,no.1(January 10, 2012)
• ISSN：1520-5827

文摘

The aggregation of insulin is complicated by the coexistence of various multimers, especially in the presence of Zn²⁺. Most investigations of insulin multimerization tend to overlook aggregation kinetics, while studies of insulin aggregation generally pay little attention to multimerization. A clear understanding of the starting multimer state of insulin is necessary for the elucidation of its aggregation mechanism. In this work, the native-state aggregation of insulin as either the Zn鈥搃nsulin hexamer or the Zn-free dimer was studied by turbidimetry and dynamic light scattering, at low ionic strength and pH near pI. The two states were achieved by varying the Zn²⁺ content of insulin at low concentrations, in accordance with size-exclusion chromatography results and literature findings (Tantipolphan, R.; Romeijn, S.; Engelsman, J. d.; Torosantucci, R.; Rasmussen, T.; Jiskoot, W. J. Pharm. Biomed. 2010, 52, 195). The much greater aggregation rate and limiting turbidity (蟿_{鈭?/sub>) for the Zn鈥搃nsulin hexamer relative to the Zn-free dimer was explained by their different aggregation mechanisms. Sequential first-order kinetic regimes and the concentration dependence of 蟿鈭?/sub> for the Zn鈥搃nsulin hexamer indicate a nucleation and growth mechanism, as proposed by Wang and Kurganov (Wang, K.; Kurganov, B. I. Biophys. Chem. 2003, 106, 97). The pure second-order process for the Zn-free dimer suggests isodesmic aggregation, consistent with the literature. The aggregation behavior at an intermediate Zn²⁺ concentration appears to be the sum of the two processes.}