I hope to grafting amino-sugar to gelatin backbone by using EDC/NHS coupling method.

I want to do this reaction in water with neutral pH or slightly acidic (pH 5-6), as I know in this condition, the activation of carboxyl group in gelatin will proceed well and acidic condition somehow can prevent the addition of activate carboxyl group to the amino group on the gelatin backbone.

Amino-sugar (hydrochloride salt type) is changed into free amine by stirring with organic base (DIEA, Et3N) in water. Then this solution was added dropwise to the activate gelatin solution (above) and stirring at 40 degree for 24 hours.

But I'm not sure will the amino-sugar adding to gelatin solution will change to the salt type again before total coupling? Or will it also be protonate in slightly acidic condition and decrease the reactivity?