The microenvironment at the surface of hen-egg-white lysozyme (HEWL) was examined by analyzing the change in pK_a of fluorescein isothiocyanate (FITC) upon binding to the N-terminus of HEWL. The result showed that the local pH at the HEWL surface is higher than the bulk pH. Furthermore, the data showed that the difference between the local and bulk pH becomes larger with decreasing pH, suggesting HEWL repels more protons at lower pH. Because the local pH affects the protonation states of functional amino-acids at the protein surface, the results provide the fundamental insight into the microenvironment at the protein surface.

中文翻译：

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鸡蛋清溶菌酶表面的局部pH

通过分析异硫氰酸荧光素（FITC）的p K _a与HEWL的N末端结合后的变化，检查了鸡蛋-白色溶菌酶（HEWL）表面的微环境。结果表明，HEWL表面的局部pH高于整体pH。此外，数据表明，随着pH值的降低，局部pH值与整体pH值之间的差异会变大，这表明HEWL在较低pH值下会排斥更多的质子。由于局部pH值会影响蛋白质表面功能氨基酸的质子化状态，因此该结果为深入了解蛋白质表面微环境提供了基础。