  The momentum dependence of the drag coefficient of heavy quarks propagating
through quark gluon plasma (QGP) has been evaluated. The results have been used
to estimate the nuclear suppression factor of charm and bottom quarks in QGP.
We observe that the momentum dependence of the transport coefficients plays
crucial role in the suppression of the heavy quarks and consequently in
discerning the properties of QGP using heavy flavours as a probe. We show that
the large suppression of the heavy quarks observed at RHIC and LHC is
predominantly due to the radiative losses. The suppression of $D^0$ in Pb+Pb
collisions at LHC energy - recently measured by the ALICE collaboration has
also been studied.
