What is the name of substances that covalently binds proteins - (May/15/2006 )

Hi

I once was told about a substance that covalently binds proteins together, so that they are not denatured on a SDS-PAGE, even with B-mercaptoethanol in the sample buffer. But i cannot remember the name of it, except that it is a 4 letter abbreviation with many S'es. Anyone know what I'm talking about?

is it sebacic acid bis(N-succinimidyl) ester (DSS)?
Sébastien