Protein inhibition by covalent modifications has been widely explored during the last decades. Despite the worries regarding the toxicity and suitability of irreversible covalent drug inhibitors, lately they have gained more and more attention in scientific community. Here we investigate covalent modifications of non-catalytic protein residues with small-molecules as the potential building blocks for future drug discovery. The intricacies of protein structure and the environment they exist in, usually complicate the understanding of the reactivity between the amino acids and compounds. In this study, we attempted to approach this subject from an analytical point of view. By applying recombinant DNA techniques, we expressed and purified proteins of interest; using liquid chromatography–mass spectrometry (LC–MS) we attempted to label a number of redesigned proteins with the ultimate goal to apply this to human protein kinases, few of which will be presented here. This may potentially assist in rationally target residues in proteins, ideally not ctalytic ones that can be covalently modified, which can serve in later drug design studies. Furthermore, it will optimistically lead us to new efforts in discovering alternative methods of cancer treatment. Ultimately, the combination of experimental techniques and computational models will broaden our knowledge of covalent modifications at allosteric positions in proteins.