Preparation Of Grafted Amino Acids Molecularly Imprinted Membrane And Study On Its Chiral Recognition And Resolution Properties

Amino acid is the basic constituent of proteins in living organisms,and it plays an important role in the fields of drug synthesis,pesticide,food and daily chemicals and so on.Amino acid is a kind of chiral compounds,and its enantiomers have the same chemical and physical properties,but the very different biological activities.So the separation of amino acid enantiomers has been extensively studied.Membrane separation method is a more cost-effective method of resolution,but the general separation membrane lacks the selectivity of enantiomeric separation.Molecular imprinting technology and membrane technology are combined in this study to prepare amino acid single enantiomer molecular imprinting membrane,and the selectivity and split efficiency of amino acid resolution were effectively improved.In the present study,L-aspartic acid and L-glutamate acid were grafted onto the polysulfone membrane by the molecular design idea,using the new surface imprinting technique and the "A simultaneous of graft crosslinking polymerization and the molecular imprinting".L-aspartic acid molecularly imprinted membrane and L-glutamate acid molecular imprinting membrane were prepared and the identifying and permeation separation performance of the two imprinted membranes were studied.The results showed that the two kinds of imprinted membranes had excellent recognition and selectivity for the enantiomers of the two amino acids,and the chiral separation of amino acid enantiomers was achieved.The method to design and prepare grafted molecularly imprinted membrane of single amino acid enantiomers has obvious innovation.And it has important scientific value and broad application prospects in biology and medicine and other fields.Firstly,polysulfone was used as raw material to prepare chloromethylated polysulfone?CMPSF?.On the basis of the above,using N,N-dimethylacetamide as the solvent and polyethylene glycol-400 as the porogen,the asymmetric porous membrane of CMPSF was prepared by the immersion precipitation phase transformation method.Then aminated with ethylenediamine to modify it,and the aminated modified membrane AMPSF was prepared.Using ammonium persulfate as the initiator,surface-initiated polymerization of dimethylaminoethyl methacrylate?DMAEMA?was carried out on the surface of the basement membrane by-NH₂/S₂O₈^2-surface initiating system.And then the functional grafted membrane PSF-g-PDMAEMA was obtained.The effects of the main factors on the graft polymerization were investigated,and the graft polymerization conditions were optimized.The grafted membrane PSF-g-PDMAEMA was characterized by FT-IR,OM and SEM.The interaction of monomer DMAEMA with aspartic acid and glutamic acid was investigated by ultraviolet absorption spectrometry.The adsorption characteristics of grafted membrane PSF-g-PDMAEMA with aspartic acid and glutamic acid were further studied.The results showed that the graft polymerization of DMAEMA on the surface of polysulfone membrane could be successfully carried out with the amino-persulfate surface initiation system.The grafting degree increased with the increase of the amount of amine bonding on the surface of AMPSF.The optimum temperature for the polymerization is 50 ?.The suitable concentration of persulfate in the solution is 1.0 wt% of the monomer.Under suitable conditions,the grafting degree of PDMAEMA on the grafted film can reach 0.64 mg/cm2.The functional grafted membrane PSF-g-PDMAEMA can strongly absorb the aspartic acid and glutamic acid by electrostatic interaction and hydrogen bonding.And when p H was 4,it had the highest adsorption capacity,which were 1.43 mg/cm2 and 1.47 mg/cm2,respectively.Experimental results of the UV absorption spectra and the isothermal experiments showed that the functional monomer DMAEMA had a strong intermolecular interaction with the two amino acids.The results of this study provide a theoretical basis for the molecular imprinting of L-aspartic acid and L-glutamic acid on the surface of polysulfone.On the basis of the above experiment,under the-NH₂/S₂O₈^2-surface initiating system,L-aspartic acid and L-glutamic acid were used as the template molecule separately,N,N'-methylenebisacrylamide?MBA?as the crosslinking agent to prepare molecularly imprinted membrane.When template molecules were washed away,L-aspartic acid and L-glutamic acid molecular imprinting membrane were successfully prepared.The chemical structure of the imprinted membrane was characterized by FT-IR.The morphology of the imprinted membrane was observed by OM.The structure of the imprinted membrane was investigated by SEM.After being fully characterized,the influence of the main factors on the selectivity coefficient of the imprinted membrane was investigated,and the optimum conditions were determined.Finally,the binding charateristic was studied by static method and dynamic infiltration method.The separation performance of the template molecules and its chiral resolution of amino acid enantiomers were investigated.The results showed that imprinting membrane had specific selectivity and excellent binding affinity to the template molecules,and the selectivity coefficient could reach to 7.52 and 7.89 separately.Under the "door effect" and "barrier effect",imprinting membrane had a good selectivity to the template molecules and can effectively separate amino acid racemate,and the optical purity of penetrant can reach to 82%.