Aiming at the study of the effect of Trp at the α1β2 interface of hemoglobin A (=Hb) on the stability of the tetrameric form of this protein and in order to introduce an additional probe for the T->R conformational transition, we have modelled by computer and produced in E. coli three Hb mutants: β37Trp->Thr, β37Trp->Thr/ α38Thr->Trp and α38Thr->Trp. An increase in the spectroscopic transition attributed to a Trp in the α1β2 interface of Hb was observed and a variation of the tetramer<->dimer equilibrium of the hemoglobin mutants was observed. The second observation is consistent with the behaviour expected from molecular modelling computations.