Blum H, Leigh J S, Ohnishi T
Biochim Biophys Acta. 1980 Nov 20;626(1):31-40. doi: 10.1016/0005-2795(80)90194-4.
The progressive power saturation of the electron paramagnetic resonance of horse heart cytochrome c and solubilized bovine heart cytochrome oxidase has been monitored at low temperature in the presence of the relaxing agent, dysprosium. The saturation of the EPR signal of cytochrome c is relieved even at 6 K. With increasing temperature the effect is enhanced as the relaxation time of the dysprosium becomes shorter; however, the intrinsic spin-lattice relaxation time, T1, for cytochrome c decreases even more rapidly with increasing temperature. T1 for cytochrome c can be described by an intrinsic component, a component which is proportional to the concentration of dysprosium and a third component due to local binding which is independent of dysprosium concentration. The cytochrome a component of cytochrome oxidase is also affected by dysprosium. In the presence of cytochrome oxidase, T1 for cytochrome c is almost unaffected by dysprosium, indicating that access to the cytochrome c heme is blocked by the binding of c to oxidase. Based on the concentration-dependent effect of dysprosium on the lifetime of cytochrome c, it is possible to make distance estimates from the EPR active center to Dy3+. Dysprosium is therefore useful for determining the spatial relationships among paramagnetic enzyme components in a quantitative way.
在低温下，于弛豫剂镝存在的情况下，监测了马心细胞色素c和可溶牛心细胞色素氧化酶的电子顺磁共振的渐进功率饱和情况。即使在6 K时，细胞色素c的EPR信号饱和也会减轻。随着温度升高，由于镝的弛豫时间变短，这种效应会增强；然而，细胞色素c的固有自旋晶格弛豫时间T1随着温度升高下降得更快。细胞色素c的T1可以由一个固有成分、一个与镝浓度成正比的成分以及由于局部结合产生的第三个与镝浓度无关的成分来描述。细胞色素氧化酶的细胞色素a成分也受到镝的影响。在细胞色素氧化酶存在的情况下，细胞色素c的T1几乎不受镝的影响，这表明细胞色素c血红素与氧化酶的结合阻止了对其的接近。基于镝对细胞色素c寿命的浓度依赖性效应，可以从EPR活性中心到Dy3+进行距离估计。因此，镝对于以定量方式确定顺磁性酶成分之间的空间关系很有用。
