The radical chemistry of proteins is of fundamental importance in biochemistry. Radicals are involved in many enzymatic reactions. Also, oxidative damage to proteins is generally initiated by radicals. For both, knowledge of reliable X-H bond dissociation energies (BDEs, X = C, N, O, S) for amino acids in proteins is important. X-H BDEs allow to predict which hydrogen atom abstractions will be thermodynamically possible, and which lesion sites can be repaired by cellular antioxidants. Preferred sites of radical attack and hydrogen atom abstraction are those associated with the lowest energy barriers, and, according to the Bell-Evans-Polanyi principle, these reactions are typically the most exothermic. Therefore, X-H BDEs can also provide a valuable input for machine learning models for the elucidation of the kinetics and mechanisms of radical reactions in proteins.