  It is pointed out that the energy of the bound states of D-branes and strings
is determined by the central charge of the space-time supersymmetry. The
universality which is seen at the black hole horizon appears also on the
D-brane side: the total energy of the bound states of a given number of branes
has a minimum when considered as a function of the independent parameters
(moduli). This provides a new evidence that the near-horizon space-time
geometry of the dilaton black holes can be represented by the bound states of
branes. The axion-dilaton dyonic black holes have the mass formula of the
non-threshold type bound state. Upon uplifting to higher dimensions they may
give information about such states.
