Electrospray mass spectrometric analysis of poly(ethylene glycol)-protein conjugates

Proteins immobilized on polymer supports are extensively used to develop bioanalytical methods and the determination of the protein/polymer molar ratio is important both for quantifying the catalytic activity and calculating the diffusion rate of the substrates, In this paper a method, based on electrospray mass spectrometry, for characterizing subtilisin and lipase immobilized on chemically modified poly(ethylene glycol)-5000 is described, The results obtained show that this technique is particularly effective, The information provided by it can be used to optimize the synthesis of these polymer-protein conjugates as well as to evaluate the efficiency of their separation and purification.