Luidens M K, Aks C S, Zhu Q, Smith T F, MacColl R, Figge J
Albany Medical College.
Pept Res. 1993 May-Jun;6(3):134-9.
Recent improvements in circular dichroism (CD) instrumentation now allow investigators to obtain highly reliable and reproducible CD spectra in the far-UV range to near 180 nm. These advances, coupled with new computer software for spectral interpretation, allow accurate calculations of secondary structural content in proteins and polypeptides. CD is particularly reliable for the calculation of alpha-helical content. We have utilized these features to determine the propensity of alpha-helix formation in highly purified synthetic peptides corresponding to segments from proteins. We obtain CD spectra of the peptides in 90% 2,2,2-trifluoroethanol (90% TFE; an alpha-helix promoting solvent) and in 2 mM sodium dodecyl sulfate (2 mM SDS; a beta-sheet promoting solvent) to assess helix stability in these different chemical environments. Using this methodology, we demonstrate that a peptide corresponding to a biologically active segment of the human estrogen receptor forms a stable alpha-helix in both environments. In contrast, peptide segments of equal length from other steroid receptors are alpha-helical in TFE but not in 2 mM SDS. These results show that the conformation of a peptide is a function of both its amino acid sequence and the local chemical environment.
近年来，圆二色性（CD）仪器的改进使研究人员能够在远紫外范围至近180纳米处获得高度可靠且可重复的CD光谱。这些进展，再加上用于光谱解释的新计算机软件，使得能够准确计算蛋白质和多肽中的二级结构含量。CD对于计算α-螺旋含量特别可靠。我们利用这些特性来确定与蛋白质片段相对应的高度纯化的合成肽中α-螺旋形成的倾向。我们获得了肽在90% 2,2,2-三氟乙醇（90% TFE；一种促进α-螺旋形成的溶剂）和2 mM十二烷基硫酸钠（2 mM SDS；一种促进β-折叠形成的溶剂）中的CD光谱，以评估这些不同化学环境中的螺旋稳定性。使用这种方法，我们证明了与人类雌激素受体生物活性片段相对应的肽在两种环境中均形成稳定的α-螺旋。相比之下，来自其他类固醇受体的等长肽段在TFE中呈α-螺旋结构，但在2 mM SDS中则不然。这些结果表明，肽的构象是其氨基酸序列和局部化学环境的函数。
