疏水表面上吸附态溶菌酶的DSC和FTIR研究

DSC and FTIR Study of Adsorbed Lysozyme on Hydrophobic Surface

联合差示扫描量热（DSC）和傅里叶变换红外吸收光谱（FTIR）分别研究了鸡蛋白溶菌酶（Lyz）在适度疏水吸附剂（PEG-600）表面上吸附和折叠时,不同盐（硫酸铵）浓度、表面覆盖度和变性剂（盐酸胍）浓度对无水环境的吸附态天然和变性溶菌酶构象变化及热稳定性的影响。研究发现：随着硫酸铵浓度和溶菌酶表面覆盖度的增加,吸附态天然和变性溶菌酶的吸热峰温度都逐渐降低,同时在较高温度下的微扰也增多。吸附发生后,α-螺旋结构减少,β-折叠和β-转角结构增多。在FTIR图谱中,吸附态变性溶菌酶在1400～1425cm^-1处的C—C拉伸振动峰和1650～1670cm^-1处的酰胺Ⅰ带特征峰都能明显观测到。但是,与之相比,相同条件下吸附态天然溶菌酶在1650～1670cm^-1处特征峰却几乎看不到。吸附态天然溶菌酶发生了结构丢失,表现得更加不稳定。

During a process of hen egg white lysozyme adsorption and folding on a moderately hydrophobic surface （PEG-600）, the effects of salt（（NH4）2SO4） concentrations, surface coverage and denaturant（guanidine hydrochloride,GuHCl） concentrations on thermal stability and the changes in the molecular conformation of adsorbed native and denatured lysozyme without aqueous solution were studied with a combination of differential scanning calorimetry （DSC） with FTIR spectroscopy. The results showed that temperature due to endothermic peaks was reduced and the disturbance increased at higher temperature with the increase in salt concentration and surface coverage of adsorbed protein. β-Sheet and β-Turn stucture increased while α-Helix structure decreased after the adsorption. The peaks corresponding to both C—C stretching frequency in 1 400-1 425 cm^-1 and amide I band frequency in 1 650-1 670 cm^-1 of adsorbed denatured lysozyme can be detected in FTIR spectra while that due to amide I band frequency of adsorbed native lysozyme almost can’t be observed. Adsorption resulted in structural loss of adsorbed native lysozyme, whose performance was less stable.