COLLAGEN FIBRIL SURFACE - TMAFM, FEG-SEM AND FREEZE-ETCHING OBSERVATIONS

Native, unfixed collagen fibrils from rat tail tendon were dehydrated following different procedures and observed under a FEG-SEM and an AFM operated in Tapping Mode (TMAFM). Freeze-etched, untreated fibrils fr om the same tissue were also observed for comparison. The most notable features of the fibril surface, i.e., the gap/overlap alternation and three prominent intraperiod ridges, were simultaneously visible only in freeze-etched specimens, while under the SEM and the TMAFM their ap pearance was dependent on both the dehydration procedure and the visua lization technique. The different susceptibility of the collagen fibri l surface structures to various treatments clearly implies the existen ce of domains of different composition. Moreover, identical specimens were imaged differently by SEM and TMAFM, highlighting instrument-spec ific advantages and limitations. The onset of dehydration-dependent, p rocedure-specific artifacts should be considered in high-resolution st udies of connective tissues. As for any biological specimen, the final aspect of collagen fibrils is determined no less by the preliminary t reatments than by the visualization approach. (C) 1996 Wiley-Liss, Inc .