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首页> 外文期刊>Biophysical Chemistry: An International Journal Devoted to the Physical Chemistry of Biological Phenomena >THERMAL ACCESS TO AMPLIFIED CHEMICAL POTENTIAL AND THE DETERMINATION OF EQUILIBRIUM CONSTANTS IN PROTEIN SOLUTIONS AT SUBFREEZING TEMPERATURES
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THERMAL ACCESS TO AMPLIFIED CHEMICAL POTENTIAL AND THE DETERMINATION OF EQUILIBRIUM CONSTANTS IN PROTEIN SOLUTIONS AT SUBFREEZING TEMPERATURES

机译：临界温度下蛋白质溶液中化学势的热通量及平衡常数的测定

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During rapid cooling of ferric heme protein solutions containing fluoride, locally concentrated ligand cannot fully equilibrate with heme before the temperature drops below 200 K and into the range where energy is insufficient for exchange with iron-bound water. When temperature is then jumped above 200 K, exchange of fluoride for bound water is activated. Between 200 and 240 K, further fluoride complex formation takes place over several minutes; its extent is measured along the kinetic curve by reimmersing the sample into liquid nitrogen and taking EPR spectra. Kinetic curves for replacement of iron-bound water by fluoride in horse aquo-ferrimyoglobin and human aquo-ferrihemoglobin, and corresponding equilibrium constants have been obtained at temperatures between 200 and 240 K. The reaction rates are affected by sucrose. Results indicate that the kinetics of exchange of fluoride for heme-bound water at subfreezing temperatures is protein specific and not diffusion-controlled, and is not affected by the phase transition of ice which takes place at subfreezing temperature. Free energy changes accompanying these reactions are largely continuous as the systems pass from above to below freezing. [References: 38]
机译：在快速冷却包含氟化物的铁血红素蛋白溶液期间，局部浓缩的配体无法在温度降至200 K以下并进入能量不足以与结合铁的水交换的温度范围之前与血红素完全平衡。然后，当温度跃升至200 K以上时，活化氟化物交换结合水。在200至240 K之间，数分钟内会进一步形成氟化物络合物。通过将样品重新浸入液氮中并获取EPR光谱，可沿动力学曲线测量其程度。在200-240 K之间的温度下获得了马水铁蛋白红蛋白和人水铁蛋白血红蛋白中氟化物置换铁结合水的动力学曲线，以及相应的平衡常数。反应速度受蔗糖的影响。结果表明，在亚冰点温度下，氟化物交换结合血红素的水的动力学是蛋白质特异性的，不受扩散控制，并且不受亚冰点温度下冰的相变影响。随着系统从上到下冻结，伴随这些反应的自由能变化在很大程度上是连续的。 [参考：38]

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