基于固体核磁共振多次交叉极化的定量检测优化技术

The Improved Solid-state NMR Quantitative Method on the Bases of Multiple-cross Polarization Technique

多次交叉极化(multiCP)是一种耗时短、可行性高的固体核磁共振定量方法,近年来受到了广泛的关注.通过研究发现,multiCP实验参数的设置依赖于样品及基团的属性.对于样品属性差异较大的体系,其获取定量结果时的实验参数条件较苛刻.针对这一问题,本文结合LGCP(Lee-Goldburg cross polarization)技术,提出了一种multiCP的优化方案,命名为MLGCP-1.本文以L-丙氨酸、L-缬氨酸、L-丙氨酸/L-缬氨酸的混合物作为模型样品,并通过与multiCP进行对比,探讨MLGCP-1方法定量分析的可行性与优势.首先,通过对L-丙氨酸、L-缬氨酸样品基团比例的测量,发现MLGCP-1实现定量检测的参数—交叉极化接触时间(tp)范围较multiCP更宽,可由1.0~1.3 ms增至0.8~2.0 ms.此外,通过对L-缬氨酸、L-丙氨酸/L-缬氨酸中特定基团间积分比值的分析发现,MLGCP-1与multiCP相似,同样受到13C-1H交叉弛豫时间(TCH)差异度的影响.即TCH差异度越大,可定量的tp参数范围越小.但与multiCP相比,MLGCP-1对tp的宽容度更高.即对于相同的样品体系,MLGCP-1可定量的tp范围更宽.总之,与multiCP相比,MLGCP-1可实现定量表征的实验参数范围更宽,更适用于表征属性差异较大的样品体系.

Recently,multiple-cross polarization(multiCP)has attracted much interest owing to its favorable performance as a solid-state nuclear magnetic resonance quantitative method.Relating investigations revealed that the setup of multiCP parameters relies on the properties of the samples.Diverse types of samples require different parameters.To improve the tolerance to sample properties,an improved method named MLGCP-1 was proposed in this work,which employed LeeGoldburg cross polarization technique.L-alanine,L-valine and their mixtures were chosen as model samples to evaluate the performance of MLGCP-1 method.multiCP experiments were also conducted for comparison.Based on the test of molecular group ratio,it was revealed that the range of contact time tp of MLGCP-1 was larger than that of multiCP,which improved from 1.0~1.3 ms to 0.8~2.0 ms.Moreover,according to the study of L-valine and mixtures,it was revealed that the range of tp was influenced by the difference of cross relaxation time TCH.Large TCH difference limited tp range for quantification.This manner was in accordance with multiCP.However,the tp range of MLGCP-1 was markedly enlarged in comparison with multiCP,presenting higher tolerance to the sample properties.