I would guess that it may have to do with steric accessibility of the sugar
diol to the boronate on the resin. Bear in mind, this approach will only bind
gem-diols, such as mannose residues. We had great success years ago separating
a yeast produced IGF (MW ~6500) into glycoslylated and non-glycosylated forms.
Perhaps this was successful because the yeast produced glycoforms high in
mannose. At that time we used a sepharose based resin, the ToyoHass wasn't
available then.
Michael F. Rohde