A study of fibrous long spacing collagen ultrastructure and assembly by atomic force microscopy

Fibrous long spacing collagen (FLS) fibrils are collagen fibrils that displ ay a banding with periodicity greater than the 67 nm periodicity of native collagen. FLS fibrils can be formed in vitro by addition of oil-acid glycop rotein to an acidified solution of monomeric collagen, followed by dialysis of the resulting mixture. We have investigated the ultrastructure of FLS f ibrils formed in vitro using the atomic force microscope (AFM). The majorit y of the fibrils imaged showed typical diameters of similar to 150 nm and h ad a distinct banding pattern with a similar to 250 nm periodicity. However , we have also observed an additional type of FLS fibril, which is characte rized by a secondary banding pattern surrounding the primary bands. These r esults are compared with those obtained in past investigations of FLS ultra structure carried out using the transmission electron microscope (TEM). The importance of the fibril's surface topography in TEM staining patterns is discussed. Images of FLS fibrils in various stages of assembly have also be en collected, and the implications of these images in determining the mecha nism of assembly and the formation of the characteristic banding pattern of the fibrils is discussed. (C) 2000 Elsevier Science Ltd. All rights reserv ed.