Departments of Molecular Genetics, Biochemistry and Chemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada.
J Biomol NMR. 2013 Feb;55(2):211-8. doi: 10.1007/s10858-012-9694-6. Epub 2013 Jan 23.
An analytical expression is derived for the rotating frame relaxation rate, R(1ρ), of a spin exchanging between two sites with different transverse relaxation times. A number of limiting cases are examined, with the equation reducing to formulae derived previously under the assumption of equivalent relaxation rates at each site. The measurement of a pair off-resonance R(1ρ) values, with the carrier displaced equally on either side of the observed correlation, forms the basis of one of the approaches for obtaining signs of chemical shift differences, Δω, of exchanging nuclei. The results presented here establish that this method is relatively insensitive to differential transverse relaxation rates between the exchaning states, greatly simplifying the calculation of optimal parameters in R(1ρ) based experiments that are used for measurement of signs of Δω.
推导出了在两个横向弛豫时间不同的位点之间进行自旋交换的旋转框架弛豫率 R(1ρ)的解析表达式。 检查了许多极限情况，并且该方程简化为在每个位点的弛豫率相等的假设下以前推导的公式。 通过测量一对离共振 R(1ρ)值，其中载波在观察到的相关的任一侧等距移动，形成了获得交换核的化学位移差 Δω的符号的方法之一。 此处呈现的结果表明，该方法对交换状态之间的横向弛豫率差异相对不敏感，这极大地简化了基于 R(1ρ)的实验的最佳参数计算，该实验用于测量 Δω的符号。
