New aspects of polyhydroxyalkanoates: chain folding and precursor self assembly; polythioesters

聚3-羟基烷酸酯（PHA）是一类高分子量的可生物降解聚酯，是细菌的碳储备材料。聚（3-羟基丁酸酯），PHB由于其立体规则性和高熔点，可形成明确的板条形状单晶，用作可生物降解结晶塑料的模型。这是一种生物技术塑料，它在世界石油供应减少的时候拯救了我们。它起源于生物质发酵，就像酿造啤酒一样。这家工厂是以玉米为原料的生物精炼厂。该领域的研发重点是对晶体生长和生物降解过程的新认识，这是通过研究解聚合酶作为物理结构探针而产生的。提出了一种从稀PHB溶液中生长晶体的新策略，包括淬火、晶须和自组装。新获得的PHB形态表明，这种可持续塑料的生物降解是晶体生长过程的逆转。由于PHA聚酯被认为具有生物相容性，因此它们正被考虑用于生物医学应用，如骨水泥、缝合线和药物输送。与PHB一样，聚硫酯（pte）在添加巯基烷基底物的工程细菌细胞中以颗粒形式积累。与微生物氧酯相比，其物理性质有很大的不同。将研究硫-硫相互作用的作用，以寻求某些pte具有较高热稳定性的解释。

Poly(3-hydroxyalkanoates), PHA, are a family of high molecular weight biodegradable polyesters which are carbon reserve material for bacteria. Because of their stereoregularity and high melting point, poly(3-hydroxybutyrate), PHB, form well-defined lath-shape single crystals which are used as model biodegradable crystalline plastics. This is the biotech plastic that has come to the rescue as world oil supplies dwindle. Its origin is biomass fermentation, like making beer. The factory is a biorefinery with corn as the raw material. R & D in this field focuses on a new understanding of the crystal growth and biodegradation process which is generated from studies using depolymerase enzymes as physical texture probes. A new crystal growth strategy from dilute PHB solution involving quenching, whiskers and self-assembly has been proposed. The new PHB morphologies obtained suggest that biodegradation of this sustainable plastic is a reversal of the crystal growth process. Because PHA polyesters are considered biocompatible, they are being considered for biomedical applications such as bone cement, sutures and drug delivery. Like PHB, polythioesters (PTEs) accumulate as granules in engineered bacterial cells with the addition of mercaptoalkyl substrates. The physical properties vary substantially in comparison with microbial oxyesters. The role of sulfur-sulfur interactions will be studied to seek an explanation for greater thermal stability of some PTEs.