SOLUBLE EARTHWORM CUTICLE COLLAGEN: A POSSIBLE DIMER OF TROPOCOLLAGEN.

When soluble earthworm cuticle collagen molecules are subjected to the shearing forces of a flow birefringence instrument, they are broken into particles approximately half the original size. The broken particles resemble vertebrate tropocollagen molecules in their hydrodynamic properties, in levorotatory powers, and in their appearance in the electron microscope. Most significantly, the broken earthworm particles form ordered aggregates similar to the segmented-long-spacing aggregations formed by vertebrate tropocollagen. These phenomena are explained by the suggestion that earthworm collagen molecules are dimers of tropocollagen-like particles. On this basis, an explanation is presented for the lack of striations in the gross collagen fibrils of earthworm cuticle.