Sastry G M, Agmon N
Department of Physical Chemistry and the Fritz Haber Research Center, The Hebrew University, Jerusalem, Israel.
Biochemistry. 1997 Jun 10;36(23):7097-108. doi: 10.1021/bi9626057.
A quantitative model, which involves diffusion on a temperature-dependent potential, is utilized to analyze the time-dependence of geminate CO recombination to sperm whale myoglobin in a trehalose glass and the accompanying spectral shifts. Most of the recombination is inhomogeneous. This is due to higher geminate reactivity rather than slower protein relaxation. A fraction of the hemes undergoes relaxation with a concomitant increase in the barrier height for recombination. The activation energy for conformational diffusion (relaxation) is considerably lower than in glycerol/water. "Protein collapse", manifested in glycerol/water by a decrease in the equilibrium conformational separation between the bound and deoxy states, is completely prevented in trehalose. We postulate that the high internal viscosity in glycerol/water is due to dehydration of the heme pocket. Trehalose prevents the escape of the few vital internal water molecules and thus preserves the internal lability of the protein. This might be important in understanding the ability of trehalose to protect against the adverse effects of dehydration.
利用一个涉及在温度依赖势上扩散的定量模型，来分析在海藻糖玻璃中双分子CO与抹香鲸肌红蛋白重组的时间依赖性以及伴随的光谱位移。大部分重组是不均匀的。这是由于双分子反应活性较高而非蛋白质弛豫较慢。一部分血红素发生弛豫，同时重组的势垒高度增加。构象扩散（弛豫）的活化能比在甘油/水中低得多。在甘油/水中表现为结合态与脱氧态之间平衡构象间距减小的“蛋白质塌陷”，在海藻糖中完全被阻止。我们推测甘油/水中的高内粘度是由于血红素口袋脱水所致。海藻糖可防止少数关键内部水分子逸出，从而保持蛋白质的内部活性。这对于理解海藻糖防止脱水不利影响的能力可能很重要。
