聚赖氨酸为主链的牙刷状分子刷的可控合成

设计合成了溴基功能化的赖氨酸单体(Br-lys)并通过关环反应制备了对应的溴代L-赖氨酸N-羧酸酐(Br-Lys-NCA)单体.利用过渡金属引发剂Ni(COD)depe调控的NCA活性开环聚合和顺序添加单体的方法,得到了组成和结构明确的聚(ε苄氧羰基L-赖氨酸)-b-PBrLL(PZLL-PBrLL)两嵌段共聚肽.利用PZLL-b-PBrLL两嵌段共聚肽为大分子引发剂,通过ATRP引发甲基丙烯酸寡聚乙二醇酯(EGMA),合成了以聚赖氨酸为骨架的牙刷状分子刷.研究发现PZLL-PBrLL两嵌段在四氢呋喃中形成α-螺旋结构,螺旋度随着PBrLL链段的增长而降低,而PZLL-b-(PBrLL-g-PEGMA)形成部分α-螺旋构象,螺旋度随侧链PEGMA增长而减小.

SYNTHESIS OF TOOTHBRUSH COPOLYPEPTIDES BASED ON POLYLYSINE BACKBONE

A new type of toothbrush like polypeptide with poly-L-lysine(PLL) as backbone was synthesized via a combination of ring opening polymerization(ROP) and atom transfer radical polymerization(ATRP).A Nε-bromoisobutyryl functionalized Nα-CBZ-L-lysine was prepared and subsequently converted into α-amino acid N-carboxyanhydride(Br-Lys-NCA).Then,a series of well-defined PZLL-PBrLL diblock copolypeptides were prepared via Ni(COD)depe mediated living ROP and sequential monomer addition strategy.These diblock copolypeptides containing a block of bromo-functionalized poly-L-lysine were then used as macroinitiator for subsequent ATRP of EGMA monomers to make toothbrush copolypeptides.The structure and composition of block and toothbrush copolypeptides were characterized using GPC/LLS,1H-NMR and FTIR.The successful reaction and chain extensions were firstly supported from FTIR characterization for NCA characteristic absorbance.The GPC results demonstrated the apparent increase of samples' molecular weight as the linear copolypeptide was converted into copolypeptide brushes.1H-NMR spectra verified the formation of homopolypeptide and copolypeptides.The secondary structures of both block and toothbrush copolypeptides were investigated using circular dichroism(CD).It was found that the α-helical content of PZLL-b-PBrLL diblock copolypeptide decreased with the reduction of mass fraction and chain length of PZLL.For toothbrush copolypeptides,the helicity was substantially lower than corresponding diblock precursors,and decreased with growing side chain length of PEGMA.Herein,we demonstrated a facile method to synthesize the biodegradable copolypeptide toothbrush with tunable spatial configurations and secondary structures by combining NCA ring opening polymerization and controlled ATRP technology.Moreover,such strategy can be easily expanded to make temperature and pH responsive copolypeptide toothbrushes.