聚阳离子糖缀物氢键诱导TPPS手性聚集

TPPS Aggregates with Chirality Induced by Hydrogen Bonds from Polycationic Glycoconjugate

利用原子转移自由基聚合(ATRP)方法制备了亲水性嵌段聚合物聚乙二醇-b-聚甲基丙烯酸N,N-二甲氨基乙酯(PEG-b-PDMAEMA),并通过季铵化反应,得到侧链接枝不同单糖分子(葡萄糖、半乳糖、甘露糖)的聚阳离子糖缀物PEG-b-P(DMAEMA-co-DMAEMA-Sac)(Monosaccharide).研究了该聚合物与5,10,15,20-四(对磺酸基苯基)-卟啉(TPPS)在水溶液中的复合自组装行为.研究结果表明,TPPS在该组装体中以J-聚集体形式存在且显示超分子手性特征.手性信号的产生是聚合物侧链糖单元C(4)和C(5)上的羟基与TPPS通过非共价键——氢键相互作用的结果,因此手性信号方向应与糖单元构型有关.通过对比单糖构型发现,具有(4S,5R)构型的糖单元可诱导TPPS产生424 nm正Cotton效应和490 nm负Cotton效应的聚集体,具有(4R,5R)构型的糖单元可诱导TPPS产生424 nm负Cotton效应和490 nm正Cotton效应的聚集体.

A hydrophilic block copolymer poly（ethylene glycol）-block-poly（dimethylaminoethyl methacrylate）（PEG-b-PDMAEMA） was prepared via atom transfer radical polymerization（ ATRP）. Then a further side-chain-grafting of PDMAEMA blocks using a series of monosaccharide through the formation of the quaternary ammonium resulted in the copolymer PEG-b-P（ DMAEMA-co-DMAEMA-Sac）. The degree of grafting was determined by proton nuclear magnetic resonance（1H-NMR） spectroscopy. Furthermore,the selfassembly behavior of 5,10,15,20-tetrakis（4-sulfonatophenyl）-porphyrin（ TPPS） with PEG-b-P（ DMAEMAco-DMAEMA-Sac） in pH 1. 0 acidic aqueous solution was deeply studied. The ultraviolet-visible spectrum（UV-Vis） indicated that TPPS existed as J-aggregates in the core of PEG-b-P（DMAEMA-co-DMAEMA-Sac）/TPPS complex micelles. Moreover,the supramolecular chirality and its formation mechanism were studied by circular dichroism（CD） and 2D NOESY. It was revealed by CD spectrum that the chiral feature was resulting from asymmetric arrangement of TPPS in the J-aggregates and the signal amplitude increased along with the rise of monosaccharide grafting degree. At the same time,the 2D NOESY spectrum implied weak interaction between TPPS and the grafted monosaccharide. It can figure out that the interaction site of grafted monosaccharide is H-C（4） and H-C（5）. Different kinds of monosaccharide were used for contrast tests. It was worth noting that the direction of Cotton spilt signal is associated with the configuration of C（4） and C（5）. As a result,the monosaccharide with（4S,5R） configuration led to a positive Cotton signal at 424 nm and a negative one at 490 nm. On the contrary,the monosaccharide with（4R,5R） configuration led to a negative Cotton signal at 424 nm and a positive one at 490 nm. It would be possible that the supramolecular chirality may come from the hydrogen bond interaction between TPPS and hydroxyl on monosaccharide.