Study On The Synthesis And Properties Of Polypeptides With Dual Response Properties Of Temperature And PH

Since stimulus-responsive polymers undergo chemical or physical changes after being exposed to external stimuli,they have shown great application prospects in the field of analytical chemistry,and many applications related to health,energy and the environment have also been discovered.And because of its so many chemical versatility and wide range of applications,the research of stimulus-responsive polymers has always attracted wide attention.We tried to synthesize a series of temperature and pH dual response polypeptides,including ionic and non-ionic.The structure of the polymer was characterized by ¹H NMR,FTIR,and GPC,and its dual response properties of temperature and pH were studied in depth through variable temperature UV-vis and DLS.It was tried to change its response temperature by changing the structure of the polymer.The mechanism of its double response.Our research not only enriches the varieties of dual stimulus-responsive peptides,but also provides new ideas for the subsequent application of stimulus-responsive peptides in the field of biomedicine.The specific contents of this article are as follows:OEGylated polypeptide bearing triethylene glycol monomethylether(OEG₃)and poly(ethylene glycol)methyl ether 350(OEG₇)were firstly prepared by copper mediated 1,3-dipolar cycloaddition.¹H NMR,FTIR,and GPC results indicated the successful conjugation of oligo(ethylene gylcol)(OEG)pendants with high grafting efficiency(?98%).Variable temperature UV-vis spectroscopy revealed a reversible lower critical solution temperature(LCST)-type phase transition of the resulting polypeptides.The LCST-type cloud point temperature(T_cp)in the range of 20-60 ^oC can be readily tuned by changing the OEG₃ and OEG₇ composition.Thermo-and pH-responsive polypeptide was prepared by firstly conjugating of OEG and 6-aldehyde hexyl pendants,then crosslinking in the presence of 1,6-hexanediamine,yielding OEGylated polypeptide bearing pH-labile imine bonds.The resulting polypeptide showed pH-responsive property and less pronounced thermoresponsive property at high pH values(i.e.,?6.15)and noticeable thermo-and pH-dual responsive properties at low pH values(i.e.,?5.80).In Chapter 3,we developed based on poly(?-3-propyl-L-glutamate)(PPLG)and poly(?-3-methylthiopropyl-L-glutamate)(PMTPLG)A series of new ionic peptides with acetic acid side groups,PPLG with acetic acid can be easily prepared with high efficiency(?98%)through copper-catalyzed 1,3-dipolar cycloaddition reaction("click chemistry"reaction).The PMTPLG with acetic acid can be prepared by alkylation reaction with high efficiency(?98%).Among them,PPLG with carboxyl groups at room temperature undergoes a phase transition between pH 3.05 and 3.92,and when the pH is less than or equal to 3.05,the polymer shows a significant phase transition in the heating and cooling cycle,and the Tcp will decrease with the increase of pH.,Increases with the increase of polymer concentration.At room temperature,the PMTPLG directly used for alkylation and access to the carboxyl group undergoes a phase transition between pH 6.07 and 7.16,and when the pH is less than or equal to6.07,the process of polymer cooling from high temperature shows a less obvious phase transition,and the degree of phase transition will gradually disappear with the increase of pH,and increase with the increase of polymer concentration.