Jahnke W, Kessler H
Institut für Organische Chemie und Biochemie, TU München, Garching, Germany.
J Biomol NMR. 1994 Sep;4(5):735-40. doi: 10.1007/BF00404281.
Two alternative, general methods are presented that lead to enhanced signal intensity of rapidly exchanging protons. Both methods work by avoiding saturation of the water resonance, and are convenient to implement since they do not use any selective pulses. One method carefully chooses proton pulse phases and gradient strength and position in such a way that the water is realigned along the +z axis at the beginning of the acquisition time. An alternative method is proposed for cases where the pulse sequence does not allow such phase cycling. The latter uses radiation damping to bring water back to the +z axis 20-30 ms after acquisition. The methods are applied to the triple-resonance experiments HNCA, HNCO and HN(CO)CA. Both methods require pulsed B0 field gradients and can result in higher signal intensity by a factor of two or more.
本文介绍了两种通用的替代方法，可增强快速交换质子的信号强度。这两种方法均通过避免水共振饱和来实现，并且由于不使用任何选择性脉冲，因此易于实施。一种方法是精心选择质子脉冲相位、梯度强度和位置，使得在采集时间开始时水沿+z轴重新排列。对于脉冲序列不允许进行此类相位循环的情况，本文提出了另一种方法。后一种方法利用辐射阻尼在采集后20 - 30毫秒将水带回+z轴。这些方法应用于三共振实验HNCA、HNCO和HN(CO)CA。两种方法都需要脉冲B0场梯度，并且可以使信号强度提高两倍或更多。
