when i did electron microscopy, we used to 'fix' (preserve) specimens by
soaking them in mixtures of glutaraldehyde, formaldehyde and other nasty
stuff. It has the chemical effect of crosslinking the proteins. Not the
sort of thing you would want to do to your own living tissue. Or the
di-sulfide bonds in your DNA.
take care
ted gosfield
gosfield@dolphin.upenn.edu