| As a natural antibacterial agent,amino acids are widely used as sources of raw materials,low in price,and low in toxicity.Currently,amino acid antibacterial agents are mainly concentrated in amino acid ester derivatives,amino acid metal salts,and cationic antibacterial peptides.Based on this situation,this paper mainly studies the synthesis and antibacterial properties of poly?phenylacetylene?containing different?-amino acids.Serine and tyrosine were separately modified by 4-ethynylbenzoyl chloride to produce the corresponding monomer precursors?A-Ser-1-boc,A-Tyr-2-boc?.Homopolymerization of monomer precursors by a catalyst system of triethylamine/[Rh?nbd?Cl]2 resulted in the corresponding polymer precursors?p-PA-Ser-1,p-PA-Tyr-2?.Finally,Boc protecting groups in the polymer precursors were removed under acidic conditions to give the cationic polymers PA-Ser-1 and PA-Tyr-2 with serine and tyrosine respectively.Tryptophan and valine were separately modified by 4-ethynylaniline to produce the corresponding monomer precursors?A-Trp-3-boc,A-Val-4-boc?.Homopolymerization of monomer precursors by a catalyst system of triethylamine/[Rh?nbd?Cl]2 resulted in the corresponding polymer precursors?p-PA-Trp-3,p-PA-Val-4?.Finally,Boc protecting groups in the polymer precursors were removed under acidic conditions to give the cationic polymers PA-Trp-3and PA-Val-4 with tryptophan and valine respectively.The chemical structures of the synthesized compounds were systematically characterized by nuclear magnetic resonance hydrogen spectrum?1H-NMR?,fourier transform infrared spectrometer?FT-IR?,and etc.The antibacterial activity of the synthesized polymers and the corresponding monomers on Escherichia coli and Staphylococcus aureus were evaluated by the minimum inhibitory concentration?MIC?method,and the antibacterial properties of a polyester?PV-Ser-5?and its monomer?V-Ser-5?with the same serine structure as PA-Ser-1 were compared.The effects of optical activity of the amino acid,side chain structure,polymer chain structure and polymerization effect on antibacterial properties of the polymers were investigated.The serine derived polymer?or monomer?showed clear effect of polymerization,although the monomer?A-Ser-1?has no antibacterial activity,its polymer?PA-Ser-1?showed good antibacterial activity.The valine-based A-Val-4 monomer had the best antibacterial activity among the synthesized monomers,and the MIC values of A-L-Val-4 against Staphylococcus aureus were 78?g/mL,but the corresponding polymer antibacterial effect is poor.Both tyrosine and tryptophan-based monomers and polymers had lower antibacterial activity.In order to investigate influence of the main chain structure on the antimicrobial effect of the polymer,a polyacrylate?PV-Ser-5?with the same serine as PA-Ser-1 was prepared through free radical polymerization.The results of MIC test showed that the antibacterial activity of PV-Ser-5 was significantly weaker than that of PA-Ser-1,indicating that the conjugated polyacetylene main chain of PA-Ser-1 had an obvious promoting effect on its antibacterial activity. |
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