  In the spirit of general relativity, spacetime should become curved due to
the presence of a particle of a given mass and charge, We try to understand
this fact in the quantum theory of a thin shell of matter. It leads to a
generalization of the potential energy of the shell in the semiclassical
highest dominant order of Planck mass. Rather surprisingly, the quantization of
charge is obtained as a consequence of the existence of bound states and the
quantum of the squared bare electrical charge is $\hbar c/2$
