Crystal and surface structure analysis of biosynthesized aliphatic polyesters and its depolymerase

生物合成和化学合成的脂肪族聚酯的生物降解性除了与聚合物的化学结构有关外，还与聚合物的结晶度、分子取向、链排列状态和晶体表面等形态密切相关。为了从原子水平上阐明晶体区域的生物降解机理，本文研究了聚（[R]-3-羟基丁酸酯）（P(3HB)）及其共聚物，聚（[R]-3-羟基戊酸酯）（P(3HV)），聚（l -乳酸）（PLLA）的片层单晶。采用等温结晶法制备了聚（β-丙内酯）（PPL）、聚（δ-戊内酯）（PVL）、聚（4-羟基丁酸酯）（P(4HB)）、聚（ε-己内酯）（PCL）和聚（乙烯丁二酸酯）（PES），并用透射电镜和原子力显微镜对其晶体结构和形貌进行了研究。所有的单晶都是分子内单晶，这些晶体给出了很好的分辨电子衍射图。通过x射线衍射、电子衍射和计算机模拟，揭示了PPL、P （4HB）和PVL的三维晶体结构。用胞外PHB解聚酶或蛋白酶- k酶或脂肪酶对P（3HB）及其共聚物PLLA、PPL、PCL和PES进行酶解，发现酶解从晶体边缘和末端开始，而不是从晶体的链折叠表面进行，且不降低分子量和层状厚度。这些结果表明，酶活性位点的攻击发生在晶体的无序链堆积区，即分子链迁移率较高的无序侧被优先降解。用蒸汽扩散法制备了从真菌青霉中纯化的PHB解聚合酶。在同步辐射的低温条件下采集高分辨率数据。采集到的原生数据分辨率为1.7 a, R_<merge>为6.8%。少

The biodegradability of aliphatic polyesters, which are produced by biosynthesis and chemosynthesis, strongly correlated to the polymer morphology such as crystallinity, molecular orientation, chain packing state and crystal surface, in addition to the chemical structures. For elucidation of biodegradation mechanism of crystal regions by atomic level, lamellar single crystals of poly ([R]-3-hydroxybutyrate) (P(3HB)) and its copolymers, poly ([R]-3-hydroxyvalerate) (P(3HV)), poly (L-lactic acid) (PLLA). poly (β-propiolactone) (PPL), poly (δ-valerolactone) (PVL), poly (4-hydroxybutyrate) (P(4HB)), poly (ε-caprolactone) (PCL) and poly (ethylene succinate) (PES) were prepared from dilute solution by isothermal crystallization, and the crystal structures and morphologies were investigated by means of mainly transmission electron microscopy and atomic force microscopy. All single crystals were intramolecular single crystals and these crystals gave well-resolved electron diffractograms. Three … More dimensional crystal structures of PPL, P (4HB) and PVL were revealed by X-ray and electron diffractions and computer simulations.The enzymatic degradations of lamellar crystals of P(3HB) and its copolymers, PLLA, PPL, PCL and PES were carried out with extracellular PHB depolymerases or proteinase-K or lipase, and it was reveled that enzymatic degradation of lamellar crystals progressed from crystal edges and ends rather than the chain-folding surfaces of crystals without decreasing the molecular weights and lamellar thickness. These results suggest that the attack by the active site of enzyme takes place at the disordered chain-packing regions of crystals, that is, disordered lateral sides which have higher mobility of molecular chains are preferentially degraded.We succeeded to crystallize PHB depolymerase purified from Penicillium funiculosum by vapor diffusion. High-resolution data were collected under cryogenic conditions with synchrotron radiation. Native data to a resolution of 1.7 A have been collected with an R_<merge> of 6.8%. Less