Tryptophan sidechain dynamics in hydrophobic oligopeptides determined by use of 13C nuclear magnetic resonance spectroscopy.
Tryptophan sidechain dynamics in hydrophobic oligopeptides determined by use of 13C nuclear magnetic resonance spectroscopy.
复制标题
使用 13C 核磁共振波谱测定疏水性寡肽中的色氨酸侧链动力学。
DOI：
10.1016/s0006-3495(88)82925-4
复制
发表时间：
1988
影响因子：
3.4
通讯作者：
Prendergast,FG
中科院分区：
文献类型：
--
作者：
Weaver,AJ;Kemple,MD;Prendergast,FG
合成了两个寡肽t-boc-LAWAL-OMe和t-boc-LALALW-OMe，目的是通过13 C核磁共振和荧光光谱研究色氨酸残基在疏水环境中的侧链动力学。在这两种肽中，色氨酸侧链在C δ 1位置富集超过95%的13 C。自旋-晶格弛豫时间（T1）和稳态核Overhauser效应（NOE）的数据，在50.3和75.4 MHz的CD 3 OD的两种肽，并在75.4 MHz的t-boc-LALALW-OMe在溶血卵磷脂-D2 O胶束。我们采用了G. Lipari和A. Szabo（1982，J. Am. 104：4546）来解释13 C-NMR数据。计算机生成的曲线的基础上获得的实验数据在一个单一的频率证明之间的关系的有效相关时间色氨酸侧链运动（τ e），广义序参数（σ）描述的运动限制的程度，和肽（τ m）的整体相关时间。假设主要是偶极松弛，最小二乘拟合的双频弛豫数据提供这些参数的值为两种肽。然而，化学位移各向异性（CSA）的贡献，也明确评估的数据分析，并示出扰动预测的西格玛，τ e，和τ m值，并减少在非线性最小二乘分析的数据中观察到的chi（2）值。由于CSA的吲哚环13 C δ 1原子的弛豫的贡献的不确定性，非线性最小二乘分析的弛豫数据进行了适当的弛豫方程中包含和不包含CSA项。忽略CSA，与t-boc-LALALW-OMe的1.28 ns相比，预测在20 ° C下CD 3 OD中t-boc-LAWAL-OMe的总体肽相关时间为0.69 ns。给定这些τ m值并考虑到T1和NOE数据中测量误差的影响，在该各向同性环境中t-boc-LAWAL-OMe的色氨酸残基的内部动力学由τ e值范围为70至112 ps和σ值范围为0.22至0.36来描述。类似地，对于t-boc-LALALW-OMe，δ 8小于或等于τ e小于或等于93 ps，并且0.09小于或等于σ小于或等于0.17。六肽中色氨酸残基的Ch-末端位置可以解释其低阶参数。（400字处截断摘要）
Two oligopeptides, t-boc-LAWAL-OMe and t-boc-LALALW-OMe, were synthesized for the purpose of examining the sidechain dynamics of the tryptophan residue in hydrophobic environments by 13C nuclear magnetic resonance and fluorescence spectroscopy. In both peptides, the tryptophan sidechain was greater than 95% enriched with 13C at the C delta 1 position. Spin-lattice relaxation time (T1) and steady-state nuclear Overhauser effect (NOE) data were obtained at 50.3 and 75.4 MHz for both peptides in CD3OD, and at 75.4 MHz for t-boc-LALALW-OMe in lysolecithin-D2O micelles. We have adapted the model-free approach of G. Lipari and A. Szabo (1982, J. Am. Chem. Soc. 104:4546) to interpret the 13C-NMR data. Computer-generated curves based on experimental data obtained at a single frequency demonstrate relationships between an effective correlation time for tryptophan sidechain motion (tau e), a generalized order parameter (sigma) describing the extent of motional restriction, and an overall correlation time for the peptide (tau m). Assuming predominantly dipolar relaxation, least-squares fits of the dual frequency relaxation data provide values for these parameters for both peptides. The contribution of chemical shift anisotropy (CSA), however, is also explicitly assessed in the data analysis, and is shown to perturb the predicted sigma, tau e, and tau m values and to decrease chi(2) values observed in nonlinear least-squares analysis of the data. Because of uncertainty in the contribution of CSA to the relaxation of the indole ring 13C delta 1 atom, nonlinear least-squares analysis of the relaxation data were performed with and without inclusion of a CSA term in the appropriate relaxation equations. Neglecting CSA, an overall peptide correlation time of 0.69 ns is predicted for t-boc-LAWAL-OMe in CD3OD at 20 degrees C compared with 1.28 ns for t-boc-LALALW-OMe. Given these tau m values and taking into account the effect of measurement error in the T1 and NOE data, the internal dynamics of the tryptophan residue of t-boc-LAWAL-OMe in this isotropic environment are described by a range of tau e values from 70 to 112 ps and sigma values between 0.22 and 0.36. Similarly, for t-boc-LALALW-OMe, 68 less than or equal to tau e less than or equal to 93 ps and 0.09 less than or equal to sigma less than or equal to 0.17. The Ch-terminal position of the tryptophan residue in the hexapeptide may account for its lower order parameter.(ABSTRACT TRUNCATED AT 400 WORDS)