59. Romanovicz, D. K. and R. M. Brown, Jr.
1976. Biogenesis and structure of Golgi-derived cellulosic scales
in Pleurochrysis. II. Identification of the scale subcomponents,
with reference to cytochemical enzyme localization and the supermolecular
structure of the cellulosic microfibril. Applied Polymer Symp.
28:587-610. John Wiley & Sons, Inc., New York.
Intact Pleurochrysis scales can be
obtained in cell-free preparations for physical and chemical characterization.
Isolation of the scale subcomponents has been achieved by serial
extraction with trifluoroacetic acid, correlated with negative
staining to observe the extent of extraction. Compositional analysis
of the radial and amorphous subcomponents has revealed the presence
of glucose, galactose, arabinose, and fucose, as well as a peptide
constituent amounting to approximately 10% by weight. The spiral
microfibrils are cellulosic, as confirmed by infrared absorption
and x-ray diffraction, and are coated with glycopeptide rich in
hydroxyproline. Observations of negatively stained preparations
of isolated scales demonstrate that the intact cellulosic microfibril
is a continuous ribbon 37 x 50 Angstroms in cross-section and
attaining a length of approximately 14 microns. With improved
techniques yielding higher resolution (Bacitracin, uranyl acetate),
the individual cellulose microfibril is resolved into four apparent
protofibrils each 12 x 16 Angstroms in cross-section. From these
data, a macromolecular model of scale cellulose is proposed, incorporating
assumptions about the protein moiety derived from positive staining
characteristics, and crystallinity data calculated form wide angle
x-ray diffraction and infrared absorption.