PHOTORESPONSIVE POLYMERS - PHOTOMODULATION OF THE MACROMOLECULAR STRUCTURE IN POLY(L-LYSINE) CONTAINING SPIROPYRAN UNITS
PHOTORESPONSIVE POLYMERS - PHOTOMODULATION OF THE MACROMOLECULAR STRUCTURE IN POLY(L-LYSINE) CONTAINING SPIROPYRAN UNITS
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DOI：
10.1021/ma00105a042
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发表时间：
1995-01-02
期刊：
影响因子：
5.5
通讯作者：
CIARDELLI, F
中科院分区：
文献类型：
--
作者：
FISSI, A;PIERONI, O;CIARDELLI, F
将聚(L-赖氨酸)与螺吡喃试剂反应，得到侧链上分别含有46%和25%螺吡喃单元的多肽。得到的改性聚合物可溶于六氟丙醇(HFP)，表现出反向光致变色。在纯HFP中，光致变色聚合物为无规卷曲，其结构不受侧链光致异构化的影响。当将适量的助溶剂如三乙胺或甲醇添加到HFP溶液中时，暴露在可见光(500 Nm)或阳光下几秒钟会产生大分子链的螺旋--α-螺旋转变。暗反应伴随着α-螺旋含量的逐渐减少和原始无序构象的恢复。CD测量表明，光致变色侧链的光致异构化只能在HFP/Net(3)或HFP/MeOH溶剂组成的很小范围内触发大分子的螺旋跃迁；因此，螺吡喃修饰的聚(L-赖氨酸)可以被认为是具有‘门控光响应’的光响应体系的典型例子。
Poly(L-lysine) was reacted with spiropyran reagents to give polypeptides containing 46 and 25 mol % spiropyran units in the side chains. The resulting modified polymers were soluble in hexafluoro-2-propanol (HFP), where they exhibited reverse photochromism. In pure HFP, the photochromic polymers were random coils and the structure was not affected by the photoisomerization of the side chains. When appropriate amounts of cosolvents such as triethylamine or methanol were added to the HFP solutions, exposure to visible light (500 nm) or to sunlight for a few seconds produced the coil --> alpha-helix transitions of the macromolecular chains. The back-reaction in the dark was accompanied by the progressive decrease of the a-helix content and recovery of the original disordered conformation. CD measurements showed that the photoisomerization of the photochromic side chains was able to trigger the coil --> helix transition of the macromolecules only in a very narrow range of HFP/NEt(3) or HFP/MeOH solvent composition; therefore, spiropyran-modified poly(L-lysine) can be considered a typical example of photoresponsive systems having a ''gated photoresponse''.