Cross-linked proteins and peptides, and methods of making and uses of such cross-linked proteins and peptides. The cross-linked proteins and peptides have rigid, distance-matching bismethylene aryl cross-linking moieties. Compositions comprising the cross-linked proteins and peptides can be used as pharmaceutical delivery formulations. The cross-linked proteins and peptides can have improved properties, such as cell permeability, as compared to the parent protein or peptide.