STRUCTURAL STUDY OF SOLID POLYPEPTIDES ON THE BASIS OF NMR CHEMICAL SHIFT TENSORS.

利用高分辨率固体核磁共振波谱技术研究固体多肽的结构对阐明生物体系中的蛋白质结构具有重要意义。本研究的目的是探讨^<13>C和^<15>N化学位移张量分量（δ ta_<11>, δ ta_<22>, δ ta_<33>）与固体多肽的氨基酸残基性质、氨基酸序列和构象等结构之间的相关性。为此，我们合成了一些α -螺旋八肽，选择性地含有^<15> n和^<13> c标记的氨基酸残基，并具有一系列明确的氨基酸序列，以及由^<15> n标记的氨基酸残基和其他氨基酸残基组成的共肽[Asp (OBzl) ^<**>， X] ^n和[Lys (Z) ^<**>, X] ^n （X: ^<15> n的自然丰度）。结果发现，相邻氨基酸序列效应可由^<15>N和^<13>C的化学位移张量来评价。特别是^<15>N和^<13>C化学位移张量的δ _<22>对于确定共肽和蛋白质的固态构象和局部氨基酸序列是非常有用的。因此，在^<15>N和^<13>C化学位移张量的基础上，分析固态下蛋白质的局部结构成为可能。

Structural studies of solid polypeptides using a high-resolution solid-state NMR spectroscopy is important to clarify the protein structure in biological systems.The purpose of this study is to explore the correlation between the ^<13>C and ^<15>N chemical shift tensor components (delta_<11>, delta_<22>, delta_<33>) and the structure of solid polypeprtides such as the nature of amino-acid residue, amino-acid sequence and conformation.For this, we have synthesized some alpha-helix octadecapeptides containing selectively ^<15>N-and ^<13>C-labeled amino acid residue and with a series of well-defined amino acid sequence, and copolypeptides [Asp (OBzl) ^<**>, X] ^n and [Lys (Z) ^<**>, X] ^n consisting of ^<15>N-labeled amino acid residue and other amino acid residue (X : natural abundance of ^<15>N). As a result, it was found that the neighboring amino-acid sequence effect can be evaluated from the ^<15>N and ^<13>C chemical shift tensors. Especially, the delta_<22> of the ^<15>N and ^<13>C chemical shift tensors may be very useful for the determination of the conformation and local amino acid sequence of copolypeptides and proteins in the solid state. Thus, it became possible to analyze the local structure of proteins in the solid state on the basis of the ^<15>N and ^<13>C chemical shift tensors.