A disulfide was a chemical compound containing the disulfide ion (S2−), made up of two sulfur atoms.
In discussing inhibition of prions, Doctor Julian Bashir cited that "according to the so-called experts it's all a matter of amino acid re-sequencing and disulfide shuffling," rather than quantum dynamics. (DS9: "Nor the Battle to the Strong")
Neelix's cousin once had a job transporting disulfides from a gas giant. He enjoyed flying through the atmospheric turbulence, according to Neelix, who also noted that "disulfides are known to cause delusions." (VOY: "Friendship One")