Helical stability of de novo designed alpha-aminoisobutyric acid-rich peptides at high temperatures.
Helical stability of de novo designed alpha-aminoisobutyric acid-rich peptides at high temperatures.
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DOI：
10.1021/bi00008a022
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发表时间：
1995-02
期刊：
影响因子：
2.9
通讯作者：
J. D. Augspurger;V. A. Bindra;H. Scheraga;A. Kuki
中科院分区：
文献类型：
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作者：
J. D. Augspurger;V. A. Bindra;H. Scheraga;A. Kuki
用一维和二维核磁共振波谱测定了两个富含AiB的多肽iBoc-(Aib)3-DkNap-Leu-Aib-Ala-(Aib)2-NH(CH2)2OCH3(Dk4[7/9])和Ac-(Aib)2-beta-(1‘-naphthyl)Ala-(Aib)2-Phe-(Aib)2-NHMe(Nap3Phe6[6/8])的螺旋稳定性，其中括号符号表示AiB类残基的数量/总残基数量。先前在DMSO(Basu&Kuki，1993)中对Nap3Phe6[6/8]进行的2D ROESY实验表明，该化合物在20℃时采用3(10)螺旋构象。本工作的第一步是将这一技术应用于多肽Dk4[7/9]，证明它在20℃时也同样在氯仿中采用3(10)螺旋构象，然后用1D核磁共振技术分别监测了Nap3-Phe6[6/8]在DMSO中和Dk4[7/9]在C2D2Cl4中的酰胺质子位移。随着温度的升高，九聚体Dk4[7/9]没有表现出任何构象或展开转变的证据。这种九聚体的酰胺质子化学位移与温度几乎无关，这表明它保留了螺旋内的氢键，然后在120℃下用DMSO的溶剂微扰直接验证了这一点。由此产生的氢键模式证实，Dk4[7/9]在整个温度范围内在C2D2Cl4中保持其3(10)螺旋构象。这种构象安静被用来研究相同多肽结构中自由氢键和螺旋内氢键的酰胺质子移动的内在温度依赖性。实验还表明，在氢键较强的DMSO溶剂中，Nap3Phe6[6/8]在整个温度范围内保持了3(10)螺旋构象。将这些富含AIB的八聚体和非聚体在两种溶剂中的极高热稳定性与较长的富丙氨酸多肽在水中的热稳定性进行了对比。
1D and 2D NMR spectroscopy is used to determine the helical stability of two Aib-rich peptides, iBoc-(Aib)3-DkNap-Leu-Aib-Ala-(Aib)2-NH(CH2)2OCH3 (Dk4[7/9]) and Ac-(Aib)2-beta-(1'-naphthyl)Ala-(Aib)2-Phe-(Aib)2-NHMe (Nap3Phe6[6/8]), where the bracket notation indicates the number of Aib-class residues/total number of residues. 2D ROESY experiments, carried out previously on Nap3Phe6[6/8] in DMSO (Basu & Kuki, 1993), showed that this compound adopts the 3(10)-helical conformation at 20 degrees C. The first step in the present work is to apply this technique to the peptide Dk4[7/9], demonstrating that it likewise adopts the 3(10)-helical conformation in chloroform at 20 degrees C. The amide proton shifts of Nap3-Phe6[6/8] in DMSO and Dk4[7/9] in C2D2Cl4 were then monitored by means of 1D NMR over a large temperature range, up to 150 and 120 degrees C, respectively. The nonamer Dk4[7/9] exhibits no evidence of any conformational or unfolding transition as the temperature is raised. The nearly temperature independent amide proton chemical shifts of this nonamer are an indication of retention of the intrahelical hydrogen bonding, which was then verified directly by solvent perturbation with DMSO at 120 degrees C. The resulting hydrogen-bonding pattern confirms that Dk4[7/9] retains its 3(10)-helical conformation in C2D2Cl4 over the entire temperature range. This conformational quietness is exploited to examine the intrinsic temperature dependence of free versus intrahelically hydrogen bonded amide proton shifts within the same peptide structure. It is also shown that Nap3Phe6[6/8] retains its 3(10)-helical conformation over the entire temperature range in the stronger hydrogen-bonding solvent DMSO. The extreme thermal stability of these octameric and nonameric Aib-rich peptides in both solvents is contrasted with that of much longer alanine-rich peptides in water.