  We study several observables related to heavy quarks in strongly coupled
plasmas using the gauge/gravity correspondence. Besides the AdS_5 space dual to
N=4 supersymmetric Yang-Mills theory we consider large classes of theories
obtained from various deformations of the AdS_5 space. Among them are theories
that solve equations of motion of a 5-dimensional Einstein-Hilbert-scalar
action. Specifically, we calculate the screening distance of a heavy
quark-antiquark pair moving at constant velocity through the plasma, the
running coupling defined via the free energy of such a static pair, and the
energy radiation from a heavy quark forced into a circular motion in the
plasma. We find that these observables show universal behaviour in large
classes of theories. The screening distance in these classes of theories, that
is the maximal distance for which a heavy quark-antiquark pair is bound, is
found to be bounded from below by its value in N=4 super Yang-Mills theory.
