Critical cation balance in B → Z transition: role of Li+

Abstract
The sodium salt of poly(dGdC) is known to exhibit a B → Z transition in the presence of various cations and 60% alcohol. We here show that the lithium salt of poly(dGdC) does not undergo B → Z transition in the presence of 60% alcohol since Li + with its large hydration shell cannot stabilize the Z-form. On the other hand, high concentrations of Mg 2+ or micromolar concentrations of the cobalt hexamine complex which are known to stabilize the Z-form can compete with Li + for charge neutralization and hence bring about a B → Z transition in the same polymer. From the model building studies the mode of action of the cobalt—hexamine complex in stabilizing the Z-form is postulated.