Boston Biochem is now offering new ubiquitin-like affinity matrices with UBL proteins covalently coupled to agarose beads via primary amines allowing for a fully functional C-terminus. These reagents have the highest  protein:agarose coupling ratios available to maximize binding  for low abundance or low affinity proteins of interest.   They are useful for isolating various proteins such as E1 activating enzymes, E2 carrier enzymes, E3 ligases and other interacting partners.