Paramylon is the -1,3 glucan
storage carbohydrate in the euglenoid algae. Mature paramylon
granules are highly crystalline, fibrillar, and have a complex
substructure. X-ray diffraction was used to demonstrate that
mature paramylon granules are much more crystalline than immature
granules. Freeze-etch electron microscopy showed that in mature
granules, the microfibrils are organized in highly ordered arrays
while the microfibrils of immature granules are less organized.
The data suggest that the high crystallinity of paramylons due
to higher-order aggregates of microfibrils and the interaction
of water with the microfibrils. The dissolution of paramylon
was recorded by darkfield videomicroscopy. In a 0.5 N NaOH solution,
paramylon dissociates in a regular manner into its constituent
4 nm microfibrils, and the central region of the granule is the
last remaining refractile area during the dissolution process.