PEPTIDE STRUCTURE & DYNAMICS

了解肽结构和动力学非常有趣 在化学和生物学中。 EPR方法已被用于排序 双标记肽中侧链之间的距离，从而 揭示局部折叠几何形状。 最近，位点特异性旋转的EPR 标记肽已被证明是一种出色的探针 位置相关的动力学。 尽管这些 EPR 实验 大大增加了我们对肽运动的理解，许多 重要的细节仍未解决。 特别是传统的9 GHz EPR 频谱对各向异性不是特别敏感 自旋标签运动。 本地标签的全面描述 为了澄清该条款的解释，有必要动议 位置相关的动力学并有助于确定 双标签实验中的距离。 高频 EPR 已 经证明比 9 GHz 频谱对运动更敏感 短相关时间下的各向异性。 我们获得了高 基于丙氨酸的 3K-11 螺旋肽的频率 EPR 谱图 温度从 275-305 K。 3K- I I 螺旋肽，如下所示， 在半胱氨酸上用甲硫代磺酸盐 (MTSSL) 自旋进行标记 标签。 Ac-AAAAKAAAAKCAAAKA-NH2 高频 EPR 谱图显示 对运动各向异性比低频频谱更敏感 但仍然可以根据以下内容进行简单的线形分析 运动线变窄理论。 实验模拟 使用不同的自旋各向异性运动模型的光谱 附着在肽主链上的标签链正在进行中。

Understanding peptide structure and dynamics is of great interest in chemistry and biology. EPR methods have been used to rank distances between side chains in doubly labeled peptides, thereby revealing local folding geometry. Recently, EPR of site-specific spin labeled peptides has been shown to be an excellent probe of-position-dependent dynamics. Although these EPR experiments have added considerably to our understanding of peptide motions, many important details remain unresolved. In particular, conventional 9 GHz EPR spectra are not particularly sensitive to the anisotropy of the spin label motion. Thorough characterization of the local label motion is necessary in order to clarify the interpretation of the position-dependent dynamics and to aid in the determination of distances in double label experiments. High frequency EPR has been demonstrated to be more sensitive than 9 GHz spectra to motional anisotropy at short correlation times. We have obtained high frequency EPR spectra of the alanine based 3K- 11 helical peptide at temperatures from 275-305 K. The 3K- I I helical peptide, shown below, is labeled at the cysteine with a methanethiosulfonate (MTSSL) spin label. Ac-AAAAKAAAAKCAAAKA-NH2 The high frequency EPR spectra exhibit greater sensitivity to motional anisotropy than low frequency spectra but remain amenable to simple line shape analysis according to motional line narrowing theory. Simulations of the experimental spectra using different models for the anisotropic motion of the spin label chain attached to the peptide backbone are in progress.