Gibbons W A, Beyer C F, Dadok J, Sprecher R F, Wyssbrod H R
Biochemistry. 1975 Jan 28;14(2):420-9. doi: 10.1021/bi00673a032.
The cyclic decapeptide antibiotic tyrocidine A was studied by two relatively new methods, viz., correlation proton magnetic resonance (pmr) spectroscopy and double-resonance difference pmr spectroscopy. The correlation method of spectral accumulation provided pmr spectra of good resolution, and in addition the signal-to-noise ratio achieved per unit time of accumulation was much higher than that achieved by use of the conventional continuous wave (cw) method. Furthermore, when protonated solvents are used, the correlation mode of accumulation has a distinct advantage over pulse and fast Fourier transform (fft) methods currently in use. Double-resonance difference (drd) spectra of individual amino acid residues in tyrocidine A were obtained by the correlation method when the decoupling frequency was maintained at the center frequency of the appropriate C-alpha proton multiplet and at a level of power that totally decoupled vicinal C-alpha and C-beta protons; the resolution of these spectra was good, and the signal-to-noise ratio was high. The distinct patterns and spectral positions of the drd spectra were characteristic of the particular type of amino acid residue and, therefore, could be used as the basis for making assignments. Furthermore, the drd spectra revealed the spectral positions of individual C-alpha and C-beta proton transitions and therefore, upon spectral analysis, could provide the chemical shifts and coupling constants of these protons. Positions of transitions were revealed even though they were hidden by overlap in the corresponding conventional single- or double-resonance spectra.
采用两种相对较新的方法对环状十肽抗生素短杆菌酪肽A进行了研究，即关联质子磁共振（pmr）光谱法和双共振差分pmr光谱法。光谱累积的关联方法提供了高分辨率的pmr光谱，此外，单位累积时间内获得的信噪比远高于使用传统连续波（cw）方法所获得的信噪比。此外，当使用质子化溶剂时，累积的关联模式相对于目前使用的脉冲和快速傅里叶变换（fft）方法具有明显优势。当去耦频率保持在适当的C-α质子多重峰的中心频率，并处于完全去耦相邻C-α和C-β质子的功率水平时，通过关联方法获得了短杆菌酪肽A中各个氨基酸残基的双共振差分（drd）光谱；这些光谱分辨率良好，信噪比高。drd光谱独特的模式和光谱位置是特定类型氨基酸残基的特征，因此可作为进行归属的基础。此外，drd光谱揭示了各个C-α和C-β质子跃迁的光谱位置，因此，通过光谱分析，可以提供这些质子的化学位移和耦合常数。即使跃迁位置在相应的传统单共振或双共振光谱中因重叠而被隐藏，也能被揭示出来。
