  There is a considerable interest in understanding the dependence of
one-nucleon removal cross sections on the asymmetry of the neutron $S_n$ and
proton $S_p$ separation energies, following a large amount of experimental data
and theoretical analyses in a framework of sudden and eikonal approximations of
the reaction dynamics. These theoretical calculations involve both the
single-particle cross section and the shell-model description of the projectile
initial state and final states of the reaction residues. The configuration
mixing in shell-model description of nuclear states depends on the proximity of
one-nucleon decay threshold but does it depend sensitively on $S_n - S_p$? To
answer this question, we use the shell model embedded in the continuum to
investigate the dependence of one-nucleon spectroscopic factors on the
asymmetry of $S_n$ and $S_p$ for mirror nuclei $^{24}$Si, $^{24}$Ne and
$^{28}$S, $^{28}$Mg and for a series of neon isotopes ($20 \leq A \leq 28$).
