SDS-PAGE staining for digestion assay - (May/29/2012 )

i have been trying to find out the collagen degradation assay using collagenase..however, i do not get the expected bands after staining with coomassie or silver...would someone please help me out? does acetic acid used in FIXATION step drains off the collagen from the gel?? is this happening with me?

I'm not familiar with collagen degradation assay... but, acetic acid is used in fixation to help precipitate proteins in the gel to prevent them from diffusing out of the gel, thats why its called fixing (they are fixed in the gel).