Ultrastructure and assembly of segmental long spacing collagen studied by atomic force microscopy

The in vitro formation of segmental long spacing (SLS) collagen as induced by the addition of ATP to acidified Type I collagen solutions has been exam ined with the atomic force microscope (AFM). AFM images obtained suggest th at the assembly proceeds in a stepwise manner, through an intermediate stag e of oligomers, which then associate laterally to form the so-called "SLS c rystallites". Attempts to induce SLS formation by the addition of other pol yanionic species to monomeric collagen solutions met with mixed success; AT P-gamma -S and GTP produced SLS crystallites, whereas inorganic phosphate a nd other polyanionic dyes did not. This indicates that the formation of SLS cannot simply be attributed to the negation of positive charges believed t o be located on the end of the collagen monomer, but rather it is a complex function of the structure and charge of both the collagen monomer and poly anion. (C) 2000 Elsevier Science Ltd. All rights reserved.