Gao X, Wong T C
Department of Chemistry, University of Missouri, Columbia, MO 65211, USA.
Biopolymers. 2001 Jan;58(1):20-32. doi: 10.1002/1097-0282(200101)58:1<20::AID-BIP30>3.0.CO;2-3.
Three adrenocorticotropin hormone (ACTH) fragments (1-10, 1-24, and 11-24) have been studied in water and in sodium dodecylsulfate (SDS) and dodecylphosphocholine (DPC) micelles by nuclear magnetic resonance spectroscopy. The trans-cis isomerism at all three proline sites (at positions 12, 19, and 24) was found in the 11-24 segment of the peptide. The population of the cis isomers changes with the environment of the peptide. Specifically, the presence of the DPC micelle does not affect the trans-cis equilibrium in the 11-24 segment from that in water. In contrast, the presence of the SDS micelles decreases the population of the cis isomer at Pro(24), but increases its population at Pro(12) and Pro(19). The effect of SDS micelles on the trans-cis equilibrium at these proline sites was discussed. Intermolecular nuclear Overhauser effect (NOE) correlations between the ACTH peptides and the micelles were observed. These correlations occurred only in the 1-10 segment of the peptides, and the hydrophobic side chains contributed most to the intermolecular NOE. The intermolecular NOE pattern corroborates the suggestion that the 1-10 segment of the ACTH peptides bind to these micelles via a surface-binding mode, with most of the interactions coming from the insertion of the hydrophobic side chains.
通过核磁共振光谱法，对三种促肾上腺皮质激素（ACTH）片段（1-10、1-24和11-24）在水以及十二烷基硫酸钠（SDS）和十二烷基磷酰胆碱（DPC）胶束中的情况进行了研究。在该肽段的11-24片段中，发现了所有三个脯氨酸位点（第12、19和24位）的反式-顺式异构现象。顺式异构体的比例随肽段所处环境而变化。具体而言，DPC胶束的存在并不影响11-24片段在水中的反式-顺式平衡。相反，SDS胶束的存在会降低Pro(24)处顺式异构体的比例，但会增加Pro(12)和Pro(19)处顺式异构体的比例。讨论了SDS胶束对这些脯氨酸位点反式-顺式平衡的影响。观察到了ACTH肽与胶束之间的分子间核Overhauser效应（NOE）相关性。这些相关性仅出现在肽段的1-10片段中，且疏水侧链对分子间NOE贡献最大。分子间NOE模式证实了ACTH肽段的1-10片段通过表面结合模式与这些胶束结合的推测，其中大部分相互作用来自疏水侧链的插入。
