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

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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.