Virta A, Komu M, Kormano M
Department of Diagnostic Radiology, University of Turku, Finland.
Magn Reson Med. 1997 Jan;37(1):53-7. doi: 10.1002/mrm.1910370109.
The effect of molecular weight, concentration, and structure on 1/T1rho, the rotating frame relaxation rate, was investigated for several proteins using the on-resonance spin-lock technique, for locking fields B1 < 200 microT. The measured values of 1/T1rho were fitted to a simple theoretical model to obtain the dispersion curves 1/T1rho(omega1) and the relaxation rate at zero B1 field, 1/T1rho(0). 1/T1rho was highly sensitive to the molecular weight, concentration, and structure of the protein. The amount of intra- and intermolecular hydrogen and disulfide bonds especially contributed to 1/T1rho. In all samples, 1/T1rho(0) was equal to 1/T2 measured at the main magnetic field Bo = 0.1 T, but at higher locking fields the dispersion curves monotonically decreased. The results of this work indicate that a model considering the effective correlation time of molecular motions as the main determinant for T1rho relaxation in protein solutions is not valid at very low B1 fields. The underlying mechanism for the relaxation rate 1/T1rho at B1 fields below 200 microT is discussed.
使用共振自旋锁定技术，在锁定场B1<200微特斯拉的条件下，研究了分子量、浓度和结构对几种蛋白质的旋转框架弛豫率1/T1rho的影响。将测得的1/T1rho值拟合到一个简单的理论模型中，以获得色散曲线1/T1rho(ω1)和零B1场下的弛豫率1/T1rho(0)。1/T1rho对蛋白质的分子量、浓度和结构高度敏感。分子内和分子间的氢键和二硫键数量尤其对1/T1rho有贡献。在所有样品中，1/T1rho(0)等于在主磁场Bo = 0.1 T下测得的1/T2，但在较高的锁定场下，色散曲线单调下降。这项工作的结果表明，在非常低的B1场下，将分子运动的有效相关时间作为蛋白质溶液中T1rho弛豫的主要决定因素的模型是无效的。讨论了B1场低于200微特斯拉时弛豫率1/T1rho的潜在机制。
