Neutrino masses and proton decay in SO(10)

We consider the constraints on SO(10) unified models coming from the lower limits on proton lifetime and on the scale of B-L symmetry breaking within the framework of the seesaw model for neutrino masses. By upgrading a triangular relationship for the inverse of Majorana masses to the experimental situation with non maximal 2-3 mixing and non vanishing 1-3 mixing, we get for the sum of neutrino masses the upper limit 0.16 eV.