NITROXIDE SIDE CHAIN DYNAMICS IN SPIN LABELED HELIX FORMING PEPTIDE

进行了高频电子顺磁共振 在流体水溶液中的氮氧化物自旋标记的多肽。这个 肽，跟在单个字母序列之后 AC-(AAAAK)2CAAAKA-NH2与甲硫磺酸盐自旋反应 在半胱氨酸硫磺上贴上标签。高频的自旋灵敏度 EPR非常好，只需不到50毫微克的样品就可以 获得具有良好信噪比的光谱。的模拟 依赖于温度的光谱线型揭示了 含运动的氮氧化物N-0键的局部各向异性运动 各向异性，rl/，rll(=-N)在306K时接近2.6。 之前对刚性标记多肽的研究表明，自旋标记 正在重新调整其侧链系绳的方向。这项研究表明 对生物样品进行140 GHz电子顺磁共振的可行性 液体溶液。

High frequency electron paramagnetic resonance has been performed on a nitroxide spin labeled peptide in fluid aqueous solution. The peptide, which follows the single letter sequence Ac-(AAAAK)2CAAAKA-NH2 was reacted with the methanethiosulfonate spin label at the cystein sulfur. The spin sensitivity of high frequency EPR is excellent with less than fifty nanograms of sample required to obtain spectra with good signal-to-noise ratios. Simulation of the temperature-dependent spectral lineshapes reveals the existence of local anisotropic motion about the nitroxide N-0 bond with a motional anisotropy ,rl/,rll (=- N) approaching 2.6 at 306 K. Comparison with previous work on rigidly labeled peptides suggests that the spin label is reorienting about its side chain tether. The study demonstrated the feasibility of performing 140 GHz EPR on biological samples in fluid solution.