| Co-Investigator(Kenkyū-buntansha) |
HISANO Tamao RIKEN Institute, Theoretical Structural Biology Laboratory, Research Scientist, 理論構造生物学研究室, 研究員 (20312267)
HIRAISHI Tomohiro RIKEN Institute, Polymer Chemistry Laboratory, Research Scientist, 高分子化学研究室, 研究員 (20321804)
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| Research Abstract |
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
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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
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