DFT investigation of the interaction between gold(I) complexes and the active site of thioredoxin reductase

The binding of the [Au(PMe₃)]⁺ fragment to cysteine, selenocysteine and the tetrapeptides H₂NGlyCysAGlyCOOH (A = Cys, Sec) has been investigated by DFT methods as a model for the binding of gold(I) to the selenium-containing active site of thioredoxin reductase. The calculations demonstrate both a higher acidity of Se-H compared to S-H and a stronger binding of gold at the selenium site compared to sulphur. Se-H dissociation at the selenium site increases the reducing power of the tetrapeptide H₂NGlyCysSecGlyCOOH whilst gold coordination at selenium has the opposite effect.