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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >CO Rebinding Kinetics to Myoglobin- and R-State-Hemoglobin-Doped Silica Gels in the Presence of Glycerol
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CO Rebinding Kinetics to Myoglobin- and R-State-Hemoglobin-Doped Silica Gels in the Presence of Glycerol

机译：CO在甘油存在下对肌红蛋白和R-状态-血红蛋白掺杂的硅胶凝胶的重新结合动力学

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摘要

This study characterizes the CO rebinding kinetics after photodissociation of horse heart myoglobin (Mb) and human R-state hemoglobin (Hb) encapsulated in wet silica gels, in the presence of various concentrations of glycerol. The geminate yield for HbCO is scarcely affected by the gel matrix, indicating that the proteincan fluctuate as in a homogeneous solution. On the contrary, the geminate yield for gel-embedded MbCO is much higher than that in solution, suggesting that the gel matrix inhibits the movements of the protein. The geminate yield for both proteins increases substantially with the addition of glycerol to the bathing solution. The observed kinetics could be rationalized using a simple three-state model. Rate constants have been modeled using a modified Kramers equation, which indicated that the gel exerts an internal friction on the elementary rate constants. The rate constant for geminate rebinding, k_(CA), is essentially viscosity independent below approx 20 cP for both proteins. The internal friction for the ligand escape rate, k_(CS), is much smaller and is found to be negligible for HbCO and approx5 cP for MbCO. The activation barrier for k_(CS) increases with glycerol concentration in response to increased viscosity and reduced ligand solubility. The rate k_(SC) showed a complex behavior that reflects the opposing effects of viscosity and activity arising from molecular confinement and crowding. Accordingly, the corresponding activation barriers show a biphasic behavior, with a minimum at approx =40% glycerol for HbCO and at approx =75% glycerol for MbCO. The results highlight the potential of silica gel encapsulation for in vitro studies aimed to reproduce the crowded and confined environment experienced by proteins in vivo. The diverse response to encapsulation of Mb and Hb could actually reflect physiologically relevant functional properties escaping detection in the diluted solutions normally used for biophysical investigations.
机译：这项研究的特点是在各种浓度的甘油存在下，马心肌红蛋白（Mb）和封装在湿硅胶中的人R-状态血红蛋白（Hb）光解后，CO的重新结合动力学。 HbCO的发芽率几乎不受凝胶基质的影响，表明该蛋白可以像在均匀溶液中一样波动。相反，嵌入凝胶的MbCO的发芽率要比溶液中的发芽率高得多，这表明凝胶基质抑制了蛋白质的运动。随着甘油向浴液中的添加，两种蛋白质的发芽率都显着提高。可以使用简单的三态模型使观察到的动力学合理化。速率常数已使用改良的Kramers方程建模，该方程式表明凝胶对基本速率常数产生内摩擦。两种蛋白质的双联体重新结合的速率常数k_（CA）本质上是粘度无关的。配体逸出速率k_（CS）的内摩擦小得多，发现对于HbCO而言是微不足道的，而对于MbCO而言约为5 cP。响应于粘度增加和配体溶解度降低，k_（CS）的活化势垒随甘油浓度的增加而增加。速率k_（SC）显示出复杂的行为，反映了分子限制和拥挤引起的粘度和活性的相反作用。因此，相应的活化势垒表现出两相行为，对于HbCO，最低约为甘油的约40％，对于MbCO，最低约为甘油的约75％。结果突出了硅胶封装在体外研究中的潜力，该研究旨在重现体内蛋白质所经历的拥挤和密闭环境。对Mb和Hb封装的不同反应实际上可以反映生理相关的功能特性，从而避免了通常用于生物物理研究的稀释溶液中的检测。

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