Using Paramagnetism to Slow Down Nuclear Relaxation in Protein NMR
Using Paramagnetism to Slow Down Nuclear Relaxation in Protein NMR
复制标题
在蛋白质 NMR 中利用顺磁性减缓核弛豫
DOI：
10.1021/acs.jpclett.6b02417
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Orton H
中科院分区：
文献类型：
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作者：
Orton H
顺磁性金属离子加速核自旋弛豫;这种效应被广泛用于距离测量，称为顺磁性弛豫增强（PRE）。理论预测表明，在特殊情况下，也有可能实现核弛豫率的降低（负PRE）。如果在抗磁性状态下的核弛豫机制被金属离子引起的顺磁性弛豫机制抵消，则会发生这种情况。在这里，我们报告的第一个实验证据，这样的互相关效应。使用负载Tm 3+或Tb 3+的钙结合蛋白D9 k的均匀15 N标记的突变体，与抗磁性参考（负载Y3+的相同蛋白质）相比，观察到骨架15 N自旋的R1和R2弛豫速率降低。这种效应是由未成对电子自旋产生的各向异性偶极屏蔽对化学位移各向异性张量的补偿引起的。
Paramagnetic metal ions accelerate nuclear spin relaxation; this effect is widely used for distance measurement and called paramagnetic relaxation enhancement (PRE). Theoretical predictions established that, under special circumstances, it is also possible to achieve areductionin nuclear relaxation rates (negative PRE). This situation would occur if the mechanism of nuclear relaxation in the diamagnetic state is counterbalanced by a paramagnetic relaxation mechanism caused by the metal ion. Here we report the first experimental evidence for such a cross-correlation effect. Using a uniformly15N-labeled mutant of calbindin D9kloaded with either Tm3+or Tb3+, reducedR1andR2relaxation rates of backbone15N spins were observed compared with the diamagnetic reference (the same protein loaded with Y3+). The effect arises from the compensation of the chemical shift anisotropy tensor by the anisotropic dipolar shielding generated by the unpaired electron spin.