  The incorporation of running $\alpha_s$ for the gluon emission vertex in
calculations of radiative parton energy loss in a quark-gluon plasma is
discussed. It is argued that the virtuality scale for running $\alpha_s$ for
induced gluon emission is determined by the square of the transverse momentum
of the emitted gluon rather than by the square of the invariant mass of the
final two-parton state often used in the literature.
