Ultrastructural aspects of phytoglycogen from cryo-transmission electron microscopy and quasi-elastic light scattering data.
Phytoglycogen particles extracted from the sugary maize mutant su 1 and dispersed in water were studied using transmission electron microscopy (TEM) and light scattering. Dried specimens were either negatively stained with uranyl acetate or shadowed with W/Ta. Frozen-hydrated unstained particles embedded in a thin film of vitreous ice were also observed using cryo-TEM. The particles exhibited a spheroidal shape, with a diameter ranging from 30 to 100 nm. Some of them presented a multilobular morphology and appeared to be formed by smaller subunits, 20-30 nm in diameter, resembling the described beta-particles for animal glycogen. The diameter of stained and ice-embedded particles was measured from electron micrographs. The corresponding size distribution histograms showed that the average weight diameter of ice-embedded particles was higher than that of stained ones. In the latter case, a shrinkage of the particle was believed to occur during the drying process. Light scattering experiments confirmed the diameter of ice-embedded particles and indicated that they could be considered as uniformly dense spheroidal objects.
Putaux
J L
JL
Centre de Recherches sur les Macromolécules Végétales-CNRS, Grenoble, France. putaux@cermav.cnrs.fr
Buléon
A
A
Borsali
R
R
Chanzy
H
H
D020285:Cryoelectron Microscopy / Q000379:methods*; D006003:Glycogen / Q000737:chemistry* / Q000648:ultrastructure*; D008027:Light; D008853:Microscopy; D008854:Microscopy, Electron; D010316:Particle Size; D010940:Plant Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D012542:Scattering, Radiation; D003313:Zea mays / Q000648:ultrastructure
D010940:Plant Proteins; D006003:Glycogen