  Recently we provided a microscopic derivation of the exact supergravity
profile for the twisted scalar field emitted by systems of fractional D3-branes
at a Z2 orbifold singularity. In this contribution we focus on a set-up
supporting an N = 2 SYM theory with SU(2) gauge group and Nf=4. We take into
account the tower of D-instanton corrections to the source terms for the
twisted scalar and find that its profile can be expressed in terms of the
chiral ring elements of the gauge theory. We show how the twisted scalar, which
at the perturbative level represents the gravity counterpart of the gauge
coupling, at the non-perturbative level is related to the effective gauge
coupling in an interestingly modified way.
