The self-consistent Green's functions method is employed to study the spectroscopic factors of quasiparticle states around 16,28 O and 40,60 Ca . The Faddeev random phase approximation (FRPA) is used to account for the coupling of particles with collective excitation modes. Results for 16 O are reviewed first. The same approach is applied to isotopes with large proton-neutron asymmetry to estimate its effect on spectroscopic factors. The results, based on the chiral N3LO force, exhibit an asymmetry dependence similar to that observed in heavy-ion knockout experiments but weaker in magnitude.