What do we do in step B? Well, now in step B, once we have the separation of these four fragments, we now want to expose the sheet that contains these separated proteins to special type of chemicals. So we essentially vaporize the chemical and we expose our sheet to this chemical that essentially breaks our disulfide bond. So the sheet is now exposed to a chemical, namely a performic acid. So the vaporized version of formic acid and that performic acid breaks those disulfide bonds. And now these fragments that were initially connected are no longer connected because these two bonds are broken by the vaporized performic acid.