The effects of small neutral osmolytes on the conformation and elastic properties of DNA are examined using a combination of experimental and theoretical techniques. Under certain conditions, several chemically distinct osmolytes induce a similar structural change in DNA. This change is well correlated with the change in water activity when osmolyte is introduced into the system as an osmotic stressing agent. The dependence of the observed transition on water activity and only slight dependence of the transition on the particular osmolyte used suggests that the controlling factor in the structural change is the level of hydration of DNA, not particular interactions of osmolyte with the macromolecule. These findings are the motivation behind efforts to develop a theoretical basis on which to better understand the hydration of macromolecules in multi-component systems.
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