Department of Chemistry, Sonoma State University, 1801 East Cotati Avenue, Rohnert Park, CA 94928, USA.
Biophys Chem. 2009 Dec;145(2-3):72-8. doi: 10.1016/j.bpc.2009.09.002. Epub 2009 Sep 12.
As more peptide secondary structures deduced by infrared spectroscopy (IR) have been reported in the literature, there have been overlaps in assignments of elements of secondary structure to carbonyl vibrational frequencies. We have investigated this phenomenon with regards to the use of IR for monitoring membrane-induced structural changes using conformationally diverse peptides. These IR studies, complemented by circular dichroism (CD) experiments, revealed that peptide-solvent interactions can mask membrane-induced conformational changes monitored by IR. A structural transition from random coil to alpha-helix upon the binding of mastoparan X to a membrane was clearly observed by CD but obscured in the amide I region of the IR spectrum. In addition, unlike the buried helical peptides gramicidin D and P16 in micelles, the amide II peak for mastoparan X was absent, likely due to H-D exchange. This suggests information on the peptide's membrane-bound solvent accessibility could be obtained from this region of the spectrum.
随着越来越多的肽二级结构通过红外光谱（IR）推断出来，二级结构的元素与羰基振动频率的分配已经出现重叠。我们使用结构多样化的肽，针对使用 IR 监测膜诱导结构变化的情况，调查了这种现象。这些 IR 研究，辅以圆二色性（CD）实验，表明肽-溶剂相互作用可以掩盖通过 IR 监测的膜诱导构象变化。通过 CD 清楚地观察到 mastoparan X 与膜结合后从无规卷曲到α-螺旋的结构转变，但在 IR 光谱的酰胺 I 区域中被掩盖。此外，与胶束中的埋藏螺旋肽 gramicidin D 和 P16 不同，mastoparan X 的酰胺 II 峰不存在，可能是由于 H-D 交换。这表明可以从光谱的这一区域获得有关肽的膜结合溶剂可及性的信息。
