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用差示扫描量热计,在不同pH值的各种缓冲溶液内、在不同浓度的两种中性盐溶液内,研究了牛红细胞超氧化物歧化酶(SOD)的热变性过程.实验表明PIPES是一个不与SOD结合的缓冲剂;阴离子的结合或多或少地影响热变性过程,且对该酶的氧化形式的影响更显著。实验发现在不同的缓冲溶液内,在高于等电点的合适的pH值处,或者在浓度较高的中性盐溶液内,SOD能形成一种热稳定性较低的新构象。它受热后不可逆地转变成常见的高热稳定性的构象。依据无盐蒸馏水中得到的热力学参数,运用Ooi模型和热力学分析揭示出高值的纯构象变性焓△H_d~c是SOD高热稳定性的热力学原因。
Thermal denaturation of bovine erythrocyte superoxide dismutase (SOD) was studied by differential scanning calorimetry in different pH buffer solutions with different concentrations of two neutral salt solutions. PIPES is a buffer that does not bind to SOD; the binding of anions affects thermal denaturation more or less, and the effect on the oxidized form of the enzyme is more pronounced. It has been found experimentally that SOD can form a new thermosensitive new conformation in different buffer solutions, at a suitable pH above the isoelectric point or in more concentrated neutral salt solutions. It reverses irreversibly after heating into the common conformation of high thermal stability. Based on the thermodynamic parameters obtained from the salt-free distilled water, using the Ooi model and the thermodynamic analysis revealed that the high pure conformational enthalpy △ H_d ~ c is the thermodynamic cause of the high thermal stability of SOD.