Protein drug conjugate exercise

I am supposed to draw the structure of a derivative of the following structure which could be used to make a protein drug conjugate. And then I should draw the reaction for the protein modification. So I thought it would be easiest to turn the carboxylic acid into an aldehyde and use this as the derivative. Then the aldehyde and primary amine on the protein could form a imine. I am not a chemist or pharmacist. So it's been a while since I had to do organic chemistry and I don't have solutions for this exercise. So does this derivative and reaction make sense?

• The reaction for formation of imine is correct, as far as I (not an expert) can tell. Before that you'll need to reduce the acid to aldehyde, though. Whether this will work as a protein drug conjugate or not - I frankly haven't got the faintest idea – TRC Jul 21 at 15:38