Circular dichroism spectra of short, fixed-nucleus alanine helices
Circular dichroism spectra of short, fixed-nucleus alanine helices
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DOI：
10.1073/pnas.232591399
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发表时间：
2002-11-26
影响因子：
11.1
通讯作者：
Baldwin, RL
中科院分区：
文献类型：
--
作者：
Chin, DH;Woody, RW;Baldwin, RL
非常短的丙氨酸肽螺旋可以在固定核中研究，螺旋形成系统[Siedlicka， M., Goch， G., Ejchart, a ., Sticht， H. & Bierzynski, a . (1999) Proc. Natl。国家科学。[j]。在取自EF-hand蛋白的12个残基序列中，当肽与La3+结合时，4个C端肽单元变为螺旋状，并且通过在C端添加丙氨酸残基可以形成更长的螺旋。这里研究的螺旋包含4、8或11个肽单位。令人惊讶的是，根据这里报道的圆二色性结果，这些短的固定核螺旋在4到65度范围内几乎保持完全的螺旋状，这与最近报道的滴定量热法结果一致。这些肽在这里用来定义短螺旋的圆二色性，这是精确测量螺旋倾向所需要的。两个显著的性质是：(1)平均肽椭圆度的温度系数强烈依赖于螺旋长度；而且，如果信号强度随螺旋长度（对于非常短的螺旋）下降的速度比过去假设的要慢得多。根据实验确定的NV1跃迁矩方向，将短螺旋的圆二色光谱与新的理论计算结果进行了比较。
Very short alanine peptide helices can be studied in a fixed-nucleus, helix-forming system [Siedlicka, M., Goch, G., Ejchart, A., Sticht, H. & Bierzynski, A. (1999) Proc. Natl. Acad Sci. USA 96, 903-908]. In a 12-residue sequence taken from an EF-hand protein, the four C-terminal peptide units become helical when the peptide binds La3+, and somewhat longer helices may be made by adding alanine residues at the C terminus. The helices studied here contain 4, 8, or 11 peptide units. Surprisingly, these short fixed-nucleus helices remain almost fully helical from 4 to 65degreesC, according to circular dichroism results reported here, and in agreement with titration calorimetry results reported recently. These peptides are used here to define the circular dichroism properties of short helices, which are needed for accurate measurement of helix propensities. Two striking properties are: (i) the temperature coefficient of mean peptide ellipticity depends strongly on helix length; and (it) the intensity of the signal decreases much less rapidly with helix length, for very short helices, than supposed in the past. The circular dichroism spectra of the short helices are compared with new theoretical calculations, based on the experimentally determined direction of the NV1 transition moment.