  It is shown that a Coulomb suppression of the stellar enhancement factor
occurs in many endothermic reactions at and far from stability. Contrary to
common assumptions, reaction measurements for astrophysics with minimal impact
of stellar enhancement should be preferably performed for those reactions
instead of their reverses, despite of their negative reaction Q-value. As a
demonstration, the cross section of the astrophysically relevant 85Rb(p,n)85Sr
reaction has been measured by activation between 2.16<=E_{c.m.}<= 3.96 MeV and
the astrophysical reaction rates at p-process temperatures for (p,n) as well as
(n,p) are directly inferred from the data. Additionally, our results confirm a
previously derived modification of a global optical proton potential. The
presented arguments are also relevant for other alpha- and proton-induced
reactions in the p-, rp-, and nu-p-processes.
