Ramadhar Timothy R, Amador Fernando, Ditty Michael J T, Power William P
Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1.
Magn Reson Chem. 2008 Jan;46(1):30-5. doi: 10.1002/mrc.2118.
The growing importance of solid-phase peptide synthesis (SPPS) has necessitated the development of spectroscopic experiments that can be used to obtain structural and conformational information on resin-bound peptides. Despite the utility of two-dimensional high-resolution magic angle spinning (HRMAS) NMR experiments that provide homonuclear shift correlations, experiments that provide heteronuclear shift correlations are necessary for complex conformational and structural elucidatory problems. Here we report the optimization and implementation of non-gradient inverse NMR experiments for acquiring the 1H-13C shift correlations of resin-bound peptides. The use of non-gradient experiments is advantageous as many magic angle spinning (MAS) probes do not possess gradient coils. An HRMAS BIRD-HMQC experiment with a reduced 1JCH constant has proven very suitable for obtaining one-bond correlations. Long-range correlations can be interpolated by using a non-gradient HRMAS CT-HMBC-1 experiment where the resulting data is processed with forward linear prediction. It has been shown that removing the effects of 1H-1H J-modulation is crucial in order to view cross peaks that correspond to long-range correlations. Additionally, both experiments prove extremely useful over routine one-dimensional 13C HRMAS experiments for extracting carbon chemical shift data. The non-gradient HRMAS BIRD-HMQC and CT-HMBC-1 experiments can be used to assist in conformational analysis and to identify and deconvolute situations where accidental equivalence and seemingly correlated isochronous signals arise.
固相肽合成（SPPS）的重要性日益增加，因此有必要开发光谱实验，用于获取树脂结合肽的结构和构象信息。尽管二维高分辨率魔角旋转（HRMAS）核磁共振实验可提供同核位移相关性，但对于复杂的构象和结构解析问题，提供异核位移相关性的实验是必要的。在此，我们报告了用于获取树脂结合肽的1H-13C位移相关性的非梯度反向核磁共振实验的优化和实施。使用非梯度实验具有优势，因为许多魔角旋转（MAS）探头不具备梯度线圈。具有降低的1JCH常数的HRMAS BIRD-HMQC实验已被证明非常适合获得一键相关性。通过使用非梯度HRMAS CT-HMBC-1实验可以内插远程相关性，其中所得数据采用正向线性预测进行处理。已经表明，去除1H-1H J调制的影响对于观察对应于远程相关性的交叉峰至关重要。此外，这两个实验在提取碳化学位移数据方面比常规一维13C HRMAS实验非常有用。非梯度HRMAS BIRD-HMQC和CT-HMBC-1实验可用于辅助构象分析，并识别和反卷积出现意外等价和看似相关的等时信号的情况。
