In our simulations, when the single-chain is stretched to a prescribed end-to-end distance, R, the projected distance between backbone charges in the stretching direction becomes ℓ ≈ R/N ≈ λR 0 /N . Such conformational changes could decrease the effective 1d concentration of the backbone charges to 1/ℓ from 1/ℓ 0 . The decrease in the 1d charge density can attract fewer counterions to the backbone charges and lead to a decrease in the counterion condensation. In the opposite case of chain compression, the 1d charge density increases, and more counterions are attracted toward the backbone charges. This scenario is analogous to the alterations in the concentration of charged chain monomers in an isotropically shrinking or swelling hydrogel and consequent changes in the condensation levels . Tentatively, the changes in the 1d charge density upon deformation may be Incorporated into the Manning condensation parameter; after assuming that the Bjerrum length does not depend on the deformation, one can write f M (λ) = 1 -λR 0 /N ℓ B , which leads to a decreasing counterion condensation at λ > 0. However, in our single-chain and hydrogel-deformation simulations, we rather observe an increase until moderate stretching levels (i.e., λ ≈ 0.2) followed by a decrease at strong stretching (i.e., λ > 0.3). This suggests that, at least in part, increasing condensation levels at weak deformations are not due to a Manning-type condensation modification. One possible effect influencing the condensation behavior could be the water molecules nearby the chains. These water molecules can either sterically modify the condensation (e.g., by competing with the ions to bind to the chain backbone) or alter the dielectric constant near the chain .