Helix Stability and Transition Behavior of Helix Sense of Polypeptide

聚天冬氨酸酯由于其主链上的NH基团与侧链上的C=O基团之间的竞争性氢键作用，使其具有不稳定的螺旋结构，与稳定的聚谷氨酸酯相反。为了通过侧链-主链和侧链的相互作用来阐明聚天冬氨酸酯的螺旋稳定性和螺旋意义，合成了各种聚天冬氨酸酯，并研究了其溶液和固态圆二色谱随组成和温度的变化。聚天冬氨酸苄酯的左旋螺旋通过取代苄基到除甲基之外的烷基而转变为右旋螺旋。随着温度的升高，低烷基化程度的共聚天冬氨酸酯向右旋α-螺旋方向转变。这些行为被解释在主链和侧链之间的竞争性氢键方面。

Polyaspartic acid esters have unstable and reversed helix sense to stable Polyglutamic acid esters because of its competitive hydrogen bond between NH group in backbone and C=O group in side chain. The object of a present study is to clarify helix stability and helix sense of polyaspartic acid esters through the interaction of side chain - backbone and side chain.Various copolyaspartic acid esters were synthesized and its circular dichroism spectra in solution and solid state were examined as a function of composition and temperature. Left handed helix of polyaspartic acid benzyl esters transformed to right handed helix by the replacement of benzyl to alkyl group except for methyl group. Furthermore copolyaspartic acid esters with low alkylation transformed to right handed alpha helix sense with increasing temperature. These behavior is interpreted in terms of the competitive hydrogen bond between backbone and side chain.