Maekawa Hiroaki, Toniolo Claudio, Moretto Alessandro, Broxterman Quirinus B, Ge Nien-Hui
J Phys Chem B. 2006 Mar 30;110(12):5834-7. doi: 10.1021/jp057472q.
Femtosecond two-dimensional infrared (2D IR) spectroscopy is applied to the amide I modes of the terminally protected homo-octapeptide Z-L-(alphaMe)Val-OtBu in CDCl(3), 2,2,2-trifluoroethanol (TFE), and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) solutions to acquire 2D spectral signatures that distinguish between 3(10)- and alpha-helix structures. Suppression of diagonal peaks by controlling polarizations of IR pulses clearly reveals cross-peak patterns that are crucial for structural determination. A doublet feature is observed when the peptide ester forms a 3(10)-helix in CDCl(3) and TFE and when it is at the initial stage of 3(10)- to alpha-helix transition in HFIP. In contrast, the 2D IR spectrum shows a multiple peak pattern after the peptide ester has acidolyzed and become an alpha-helix in HFIP. Electronic circular dichroism spectra accompanying the acidolysis-driven conformational change are also reported. This is the first report on the experimental 2D IR signature of a 3(10)-helical peptide. These results, using a model octapeptide, demonstrate the powerful capability of 2D IR spectroscopy to discriminate between different helical structures.
飞秒二维红外（2D IR）光谱应用于末端保护的同型八肽Z-L-(αMe)Val-OtBu在CDCl(3)、2,2,2-三氟乙醇（TFE）和1,1,1,3,3,3-六氟-2-丙醇（HFIP）溶液中的酰胺I模式，以获取区分3(10)-螺旋和α-螺旋结构的二维光谱特征。通过控制红外脉冲的偏振来抑制对角峰，清楚地揭示了对结构测定至关重要的交叉峰模式。当肽酯在CDCl(3)和TFE中形成3(10)-螺旋时，以及在HFIP中处于从3(10)-螺旋向α-螺旋转变的初始阶段时，观察到双峰特征。相比之下，在HFIP中肽酯酸解并形成α-螺旋后，二维红外光谱显示出多峰模式。还报道了伴随酸解驱动的构象变化的电子圆二色光谱。这是关于3(10)-螺旋肽的实验二维红外特征的首次报道。这些使用模型八肽的结果证明了二维红外光谱区分不同螺旋结构的强大能力。
