  Contrary to expectations based on Harris' criterion, chain disorder with
frustration can modify the universality class of scaling at the theta
transition of heteropolymers. This is shown for a model with random two-body
potentials in 2D on the basis of exact enumeration and accurate Monte Carlo
results. When frustration grows beyond a certain finite threshold, the
temperature below which disorder becomes relevant coincides with the theta one
and scaling exponents definitely start deviating from those valid for
homopolymers.
