ATOMIC-FORCE MICROSCOPY OF COLLAGEN MOLECULES - SURFACE-MORPHOLOGY OFSEGMENT-LONG-SPACING (SLS) CRYSTALLITES OF COLLAGEN

Three-dimensional structures of laterally aggregated bundles of collag en molecules, segment-long-spacing (SLS) crystallites, were imaged by atomic force microscopy (AFM) in atmosphere. The overall image of the type I collagen SLS in a height-amplified mode was semi-cylindrical, s imilar to 300 nm in length, with two bands of elevation near both N- a nd C- ends of the molecule. Its 'cross-sectional' profile (across the molecular axis) was a smooth arch. The 'axial' profile (along the mole cular axis) had two prominent peaks similar to 250 nm apart, correspon ding to the two bands of elevation. There were several minor peaks bet ween these two prominent peaks. The elevation near both ends may be du e to the presence of covalently bound sugars near both N- and C- ends of the helical part of type I collagen a chains. The AFM images of SLS presented here indicate that the type I collagen molecule is not unif orm in diameter and has two bulged parts within its triple helix.