Atomic force microscopy of intact and digested collagen molecules

The present study was performed to analyse the structure of non-digested an d digested collagen type I molecules by atomic force microscopy (AFM). Coll agen type I molecules from the bovine skin were diluted with 0.05 N acetic acid, spread on a mica plate, air-dried and observed by non-contact mode AF M in air. Collagen molecules digested with Clostridium histolyticum collage nase were also examined by AFM. Intact collagen type I molecules were obser ved as twisted threads ranging mainly between 280 and 310 nm in length. The surface of the molecules was uneven and both ends usually slightly bulged like a globule. Depressions on the molecules were found throughout the leng th, and were most prominent similar to 70 nm from one end of the molecules. The collagenase-treated collagen molecules were degraded into fragments wi th various lengths, which corresponded to the data from sodium dodecyl sulp hate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. The end of the se fragments often appeared like a tuft, suggesting that the triple-helix u nraveled at these regions.