Peggion Cristina, Moretto Alessandro, Formaggio Fernando, Crisma Marco, Toniolo Claudio
Institute of Biomolecular Chemistry, CNR, Padova Unit, Department of Chemistry, University of Padova, 35131, Padova, Italy.
Biopolymers. 2013 Nov;100(6):621-36. doi: 10.1002/bip.22267.
The peptide 2.0(5)-helix does exist. It has been experimentally authenticated both in the crystalline state (by X-ray diffraction) and in solution (by several spectroscopic techniques). It is the most common conformation for C(α)-tetrasubstituted α-amino acids with at least two atoms in each side chain, provided that cyclization on the C(α)-atom is absent. X-Ray diffraction has allowed a detailed description of its geometrical and three-dimensional (3D)-structural features. The infrared absorption and the nuclear magnetic resonance parameters characteristics of this multiple, consecutive, fully-extended structure have been described. Conformational energy calculations are in agreement with the experimental findings. As the contribution per amino acid residue to the length of this helix is the longest possible, its exploitation as a molecular spacer is quite promising. However, it is a rather fragile 3D-structure and particularly sensitive to solvent polarity. Interestingly, in such a case, it may reversibly convert to the much shorter 3(10)-helix, thus generating an attractive molecular spring.
肽2.0(5)螺旋确实存在。它已通过晶体状态（通过X射线衍射）和溶液状态（通过几种光谱技术）得到实验验证。对于每个侧链中至少有两个原子的C(α) - 四取代α - 氨基酸，在不存在C(α) - 原子环化的情况下，它是最常见的构象。X射线衍射已对其几何和三维（3D）结构特征进行了详细描述。这种多个连续的完全伸展结构的红外吸收和核磁共振参数特征也已被描述。构象能量计算与实验结果一致。由于每个氨基酸残基对该螺旋长度的贡献是可能的最长值，因此将其用作分子间隔物很有前景。然而，它是一种相当脆弱的3D结构，对溶剂极性特别敏感。有趣的是，在这种情况下，它可能可逆地转变为短得多的3(10)螺旋，从而产生一个有吸引力的分子弹簧。
