Chapter 27. Electrospray Mass Spectrometric Characterization of Adducts Between Therapeutic Agents and Proteins

Publisher Summary Molecular mass determinations by electrospray mass spectrometry can reveal the stoichiometries of drug-protein reactions. Proper examples of analyses, where this is important, include the characterization of adducts between the therapeutic agents and proteins. The formation of covalent adducts between proteins and therapeutic agents can provide a basis for toxicity, inactivation, and drug resistance in vivo , and generally constitutes the central phenomenon in mechanism-based inhibition. Reversible adduct formation with proteins can play an important role in drug distribution, can form the basis for new drug delivery systems, and is likely to contribute to pharmacokinetic profiles. With the recent rapid development of electrospray (ES) and matrix assisted laser desorption ionization (MALDI), mass spectrometry (MS) can now be applied readily to the analysis of proteins and covalent adducts of proteins with xenobiotics, including drugs. In electrospray mass spectrometry, the sample is introduced in solution, sprayed across an electrical field in such a way that protonated or deprotonated molecules are freed from solvent and steered into the mass analyzer. These solutions are aqueous or mixtures of water and organic solvents, contain volatile electrolytes, and may be used at any pH. Electrospray is the technique of choice to interface high-performance liquid chromatography (HPLC) and capillary electrophoresis to mass spectrometers, and it has been implemented on all analyzer configurations, including magnetic sector and Fourier transform instruments.