  We study the hadron-quark phase transition in the interior of protoneutron
stars. For the hadronic sector, we use a microscopic equation of state
involving nucleons and hyperons derived within the finite-temperature
Brueckner-Bethe-Goldstone many-body theory, with realistic two-body and
three-body forces. For the description of quark matter, we employ the MIT bag
model both with a constant and a density-dependent bag parameter. We calculate
the structure of protostars within a static approach. In particular we focus on
a suitable temperature profile, suggested by dynamical calculations, which
plays a fundamental role in determining the value of the minimum gravitational
mass. The maximum mass instead depends only upon the equation of state
employed.
