The Staining Pattern of Collagen Fibrils: I. an Analysis of Electron Micrographs

Abstract

Electron micrographs of calf-skin collagen in the reconstituted native-type fibril and the segmented long spacing (SLS) forms are matched with one another and with the distribution of charged residues in the known α1 chain sequence.

It is shown that:

a) the pattern of bands in SLS corresponds closely with the charge distribution in the sequence

b) most of the bands in the fibril pattern can be matched in position (but not in intensity) to bands in the SLS pattern, confirming a substantial measure of matching of charged regions with charged regions (and therefore of hydrophobic regions with hydrophobic regions) on assembly of molecules into fibrils

c) when the al chain sequences are regularly staggered by 233 residues (to simulate the postulated packing in a fibril) the greatest concentrations of charged residues occur in regions which correspond closely with the bands in positively stained fibrils

d) the positions of the abrupt contrast steps(the overlaplgap junctions) in the image of a negatively contrasted fibril lie slightly inside the positions predicted by the sequence, indicating a more condensed conformation for the extra-helical telopeptides. This could be a consequence of the methods used for the preparation and examination of the specimen. The ratio of molecular length to fibril period is therefore uncertain in the range 4.40 to 4.53.