Käiväräinen A I, Goryunov A S, Sukhanova G
Folia Biol (Praha). 1984;30(6):396-403.
The effects of solvent viscosity and temperature on the spin-spin relaxation rates 1/T2 of solvent water protons in metmyoglobin and methaemoglobin solutions in the temperature range of 5-50 degrees C have been studied. Solvent viscosity is altered by changing sucrose concentration from 0 to 25% by weight. The magnitude of the protein contribution to the observed relaxation rate 1/T2 decreases with rising solvent viscosity at low temperatures (less than 20 degrees) in contrast to high temperatures. It is shown to be due to the decrease in the rate of exchange of the water molecules from the paramagnetic site (Fe3+ion of heme) within heme cavity with those from the bulk solvent with the rise in solvent viscosity. This effect is interpreted by the dynamic model of protein behaviour in which exchange of the water with Fe3+ion of heme is governed partly by fluctuations of heme cavities between "closed" and "open" states. This approach enables us to estimate the frequency of fluctuations of heme cavities: 7 X 10(4) sec-1 for metmyoglobin and 3 X 10(3) sec-1 for methaemoglobin.
研究了在5-50摄氏度温度范围内，溶剂粘度和温度对高铁肌红蛋白和高铁血红蛋白溶液中溶剂水质子自旋-自旋弛豫率1/T2的影响。通过将蔗糖浓度从0重量%改变到25重量%来改变溶剂粘度。与高温相比，在低温（低于20摄氏度）下，蛋白质对观察到的弛豫率1/T2的贡献幅度随着溶剂粘度的升高而降低。结果表明，这是由于随着溶剂粘度的升高，血红素腔内顺磁位点（血红素的Fe3+离子）处的水分子与本体溶剂中的水分子之间的交换速率降低所致。这种效应通过蛋白质行为的动力学模型来解释，其中水与血红素的Fe3+离子的交换部分受血红素腔在“关闭”和“开放”状态之间波动的控制。这种方法使我们能够估计血红素腔的波动频率：高铁肌红蛋白为7×10(4)秒-1，高铁血红蛋白为3×10(3)秒-1。
