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

Fibrous long spacing collagen (FLS) fibrils are collagen fibrils that display 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 glycoprotein to an acidified solution of monomeric collagen, followed by dialysis of the resulting mixture. We have investigated the ultrastructure of FLS fibrils formed in vitro using the atomic force microscope (AFM). The majority of the fibrils imaged showed typical diameters of similar to 150 nm and had a distinct banding pattern with a similar to 250 nm periodicity. However, we have also observed an additional type of FLS fibril, which is characterized by a secondary banding pattern surrounding the primary bands. These results are compared with those obtained in past investigations of FLS ultrastructure 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 been collected, and the implications of these images in determining the mechanism of assembly and the formation of the characteristic banding pattern of the fibrils is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.