【摘要】 蛋白质的初级结合水对于蛋白质分子的构象及热稳定性有着重要影响。将不同吸附水量的牛血清白蛋白样品密封入铝制挥发型样品盘中,用P/E DSC_-2型差示扫描量热计对蛋白样品的变性温度、变性焓及变性前后的比热变化等热力学参数进行测量。实验证明,随水含量增多变性温度T_D下降,当含水量R（克H₂O/克BSA）>0.24时T_D的下降渐微,当R=0.5时T_D通过最小值后又略有增大。变性焓ΔH_D也与水含量密切相关,当R<0.5时ΔH_D渐趋恒值,为200千卡/克分子。本实验还观察到在低含水量范围内0.02<R<0.24,除高温变性峰外尚有一低温峰,其峰温在0.02<R<0.07范围内随水合值增大而下降。与高温变性峰不同,此峰可逆。进一步的实验表明兔血清白蛋白及猪血清白蛋白在低含水量时亦有此前峰。实验还证实变性前后比热的改变ΔC_P与蛋白的含水量有关,当在0.02<R<0.24范围内时ΔC_P随水含量增大而下降,渐趋恒值为0.02卡/克·度。更多还原

【Abstract】 Calorimetric investigations on the thermal stability of hydrated BSA gave thefollowing results.The temperature,T_d,and the enthalpy change,H_d of denaturationat water contents below 0.5g/g(g of water per g of protein)showed strong dependenceon hydration.Below 0.5g/g water content,T_d increased gradually with decrease inwater content,when the water content is lower than 0.24g/g the increase becamemuch more marked.ΔH_d increased with increasing water content within the range0.02～0.12g/g,but decreased with increasing water content in the range 0.16～0.23g/g,then it again increased and reached a constant value of 200k-cal./mole at about0.5g/g.It is interesting to note that there was a low temperature peak in water co-ntent in the range between 0.02g/g to 0.24g/g.The transitional heat capacity cha-nge,ΔC_p,decreased with increasing water content in the range 0.02～0.24g/g.ΔC_preached a constant value of about 0.02cal./k.g.更多还原