脂肪酶N435对PBSA与PBSH的酶催化降解和分子模拟

Enzymatic Degradation of PBSA and PBSH by Lipase N435 and Its Molecular Simulation

分别采用2种酸1种醇和2种醇1种酸分别对聚丁酸丁二醇酯(PBS)改性,合成了不同化学结构的共聚酯聚(丁二酸丁二醇酯-co-己二酸丁二醇酯)(PBSA)和聚(丁二酸丁二醇-co-丁二酸己二醇酯)(PBSH),并在磷酸缓冲液以它们为底物在磷酸缓冲液中,研究了对脂肪酶N435降解反应感受性的异同。采用质量损失率和凝胶渗透色谱评价了降解前后共聚酯相对分子质量的变化;广角X衍射仪和热重分析仪分析了酶降解前后共聚酯结晶度和热性质的变化;偏光显微镜对降解后的材料进行了形貌观测。结果表明,相比于PBS,PBSA和PBSH对脂肪酶的感受性有很大提高,24 h后降解率分别达到90%和60%以上,并且PBSA降解速率比PBSH快;降解后两种共聚酯相对分子质量变化不大,但相对分子量分布系数变宽,结晶度增大;降解3 d后PBSA的热稳定性降低,而PBSH的热稳定性提高。

PBS was modified by diol and diacid separately forming two copolyesters, PBSH and PBSA, which were introduced into phosphate buffer as substrates with lipase N435 for investigating the degradation behavior. Gel permeation chromatography, thermogravimetric analysis, and wide-angle X-ray diffraction were employed to investigate the change in the molecular mass, thermal properties, and crystallinity of the copolymer before and after enzymatic degradation. Polarized optical microscopy was employed to investigate the surface morphology of the copolymers. It indicated that the sensitivity of PBSA and PBSH to lipase was significantly improved with degradation rates after 24 h greater than 90% and 60%, respectively. The degradation rate of PBSA was significantly higher than that of PBSH. The number-average molecular weight of the two copolymers changed marginally, but the molecular weight distribution became wider, and crystallinity increased. The thermal stability of PBSA decreased, while the thermal stability of PBSH improved after 3 days. The results obtained from the molecular enzymesubstrate binding model were in agreement with experimental results.