title: Factors affecting the freeze-fracture morphology of in vivo polyhydroxyalkanoate granules.
abstract: Interesting morphologies were observed when Comamonas acidovorans containing polyhydroxyalkanoates (PHA) of various compositions was freeze-fractured at temperatures far below the glass transition temperatures of PHA. In vivo granules of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) comparatively showed the most ductility, and could be stretched extensively. Contrary to the uniform needle-type deformation shown by the poly(3-hydroxybutyrate) homopolymer when fractured at -110 degrees C, copolymers containing 3-hydroxyvalerate units showed various deformation structures. Similar observations were made when in vivo granules of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) were freeze-fractured, although the ductility of the latter was much reduced. In addition, it was found that fracturing at -160 degrees C resulted in decreased ductility of the PHA granules with the concomitant increase in the number of mushroom-type deformation structures. Our results suggest that PHA granules with higher resistance to freeze-fracture deformation show less ductility, and therefore produce the mushroom-type morphology. This is the first report on the freeze-fracture morphology of PHA copolymers containing short-chain-length monomers.
authors.affiliation: Polymer Chemistry Laboratory, RIKEN Institute, Saitama, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Sudesh
authors.forename: T
authors.initials: T
authors.lastname: Fukui
authors.forename: T
authors.initials: T
authors.lastname: Iwata
authors.forename: Y
authors.initials: Y
authors.lastname: Doi
mesh_terms: D020118:Cupriavidus necator / Q000737:chemistry / Q000235:genetics; D003594:Cytoplasmic Granules / Q000737:chemistry / Q000648:ultrastructure*; D020605:Delftia acidovorans / Q000737:chemistry* / Q000254:growth & development / Q000648:ultrastructure*; D005614:Freeze Fracturing; D006885:Hydroxybutyrates / Q000737:chemistry / Q000378:metabolism; D008854:Microscopy, Electron / Q000379:methods*; D011091:Polyesters / Q000737:chemistry* / Q000378:metabolism; D011994:Recombinant Proteins; D013696:Temperature; D000094122:Polyhydroxybutyrates
chemical_list: D006885:Hydroxybutyrates; D011091:Polyesters; D011994:Recombinant Proteins; C052620:poly(3-hydroxybutyrate)-co-(3-hydroxyvalerate); D000094122:Polyhydroxybutyrates; C107955:poly(4-hydroxybutanoate); C068056:poly(3-hydroxybutyrate-co-4-hydroxybutyrate); C003182:poly-beta-hydroxybutyrate