Crystalline-structure-dependent enzymatic degradation of polymorphic poly(3-hydroxypropionate).
Crystalline-structure-dependent enzymatic degradation of polymorphic poly(3-hydroxypropionate).
复制标题
DOI：
10.1021/bm701220x
复制
发表时间：
2008-02
影响因子：
6.2
通讯作者：
Bo Zhu;Yong He;H. Nishida;Koji Yazawa;Nariaki Ishii;K. Kasuya;Y. Inoue
中科院分区：
文献类型：
--
作者：
Bo Zhu;Yong He;H. Nishida;Koji Yazawa;Nariaki Ishii;K. Kasuya;Y. Inoue
研究了具有细菌聚3-羟基烷酸S(P3HAs)基本主链结构的多晶型聚3-羟基丙酸酯(P3HP)的晶体结构对酶降解行为的影响。通过控制熔体的相对分子质量、结晶温度和/或温度，按照先前的报道(大分子2005，38,6455；大分子2006，39,194-203)，浇注或熔融结晶由β、伽马和/或三角型晶体组成的P3HP薄膜。用差示扫描量热法、广角X射线衍射仪、小角X射线散射(SAXS)和~(13)C固体核磁共振谱(SNMR)分别表征了它们的热性能、晶体结构、形貌和~(13)C固体自旋-晶格驰豫动力学。研究发现，P3HP薄膜的结晶度和片层厚度都大致按β-型和伽马型(或近似)--伽马型和三角型的顺序减小。以前的工作表明，P3HA的酶降解只取决于结晶度和片层厚度，因此它们的酶降解速率预计将按β-型和伽马型(或大约)-伽马型-β-型的顺序增加。出乎意料的是，他们的实验P3HP酶降解率在P3HA解聚酶存在的情况下以相反的顺序增加，即三角型和伽马型和贝塔型。三角型薄膜的失重率几乎比降解最快的β型薄膜小1个数量级。结果表明，晶体结构在P3HP的酶降解过程中起着决定性的作用。特别是，只有当结晶链的构象与细菌聚(3-羟基丁酸酯)(P3HB)样品的晶链构象一致，即2 1螺旋构象时，P3HP样品的降解速度才能与P3HB样品一样慢。通过比较多晶型P3HP晶体的分子相互作用和动力学，进一步阐明了P3HP独特的酶降解行为的内在原因。
The crystalline structure dependence of enzymatic degradation behavior was investigated for the polymorphic poly(3-hydroxypropionate) (P3HP), which has a basic backbone chemical structure of bacterial poly(3-hydroxyalkanoate)s (P3HAs). The P3HP films consisting of the beta-, gamma-, and/or delta-form crystal were cast or melt-crystallized as reported previously (Macromolecules 2005, 38, 6455; Macromolecules 2006, 39, 194-203) by controlling the molecular weight, crystallization temperature, and/or temperature of the melt. Their thermal properties, crystalline structures, morphologies, and (13)C solid spin-lattice relaxation dynamics were characterized by the differential scanning calorimetry, the wide-angle X-ray diffraction, the small-angle X-ray scattering (SAXS), and the (13)C solid-state NMR spectra (SNMR), respectively. Both the crystallinities and the lamellar thicknesses of P3HP films were found to decrease roughly in the order of beta-form > (or approximately) gamma-form > delta-form. From previous work, which indicates that the P3HA enzymatic degradation depends only on the degree of crystallinity and the lamellar thickness, their enzymatic degradation rates are then expected to increase in the order of beta-form < (or approximately) gamma-form < delta-form. Unexpectedly, their experimental P3HP enzymatic degradation rates in the presence of P3HA depolymerase isolated from Ralstonia pickettii T1 increase in the reverse order, i.e., delta-form < gamma-form < beta-form. The weight loss rate of the delta-form film is almost 1 order of magnitude smaller than that of the fastest degraded beta-form film. It is then strongly indicated that the crystalline structure plays a strikingly decisive role in the enzymatic degradation of P3HP. In particular, only when the conformation of crystalline chain accords with that of the bacterial poly(3-hydroxybutyrate) (P3HB) sample, i.e., the 2 1 helix conformation, is the P3HP sample degraded as slow as the P3HB sample. The inherent reason responsible for the unique P3HP enzymatic degradation behavior has been further clarified by comparing the molecular interaction and dynamics of polymorphic P3HP crystals.