I once heard that tris-glycine gels are not capable for detecting PTMs and bis-tris was. I cannot confirm this anywhere in literature. Can someone tell me if this is true or not? And if so, give an explaination why?

I have used in the past bis-tris and have detected PTMs of histones in primary macrophages by excising coomassie stained bands and tryptic digestion. But I am curious as to why tris-glycine might not work.