Reactive chemicals or metabolites can interact with proteins present in any cell type which occur at the molecular level. The electrophilic chemicals react with the nucleophilic parts of proteins, forming a covalent bond. When proteins are in their original shape they can function properly, when this is not the case the protein loses its function. These are unspecific proteins which are altered in shape due to the covalent binding of chemicals.
The determination of protein adducts can be done, but since some chemicals induce protein adducts at low abundance it is hard to measure. A new technique is developed to overcome the problem of the low abundance. A drug is labelled with a biotin affinity tag, which than can react with proteins and bind covalently. After incubation with several proteins the drugs attached to the proteins are separated from the rest of the free proteins with the use of the tag. Next the proteins which are altered by the drug can be identified with proteomics. A LC/MS/MS technique is used. A problem which can occur, is that the use of a tag can influence the binding profile of the drug. Another possibility is the use of 2D gel-electrophoresis and tandem mass spectrometry based proteomics. Proteins are purified from cells after incubation with a drug. With 2D gel-electrophoresis the proteins are separated, afterwards the spots of interest are identified with tandem mass spectrometry.