Interaction of Glutathione and Other Low-Molecular-Weight Thiols with DNA: Evidence for Counterion Condensation and Coion Depletion near DNA

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Abstract
The interaction of low-molecular-weight thiols with sonicated DNA was examined using spin filtratio to concentrate the DNA. Cationic thiols (WR1065 and cysteamine) behaved as counterions and were found to have increased concentrations in the DNA retentate relative to the filtrate. Anionic thiols (GSH, 2-mercaptoethanesulfonate, mercaptosuccinate) behaved as coions and were decreased in concentration in the DNA fraction. Concentrations of the uncharged thiol 2-mercaptoethanol were little influenced by DNA. The results demonstrate the importance of counterion near DNA. They provide a rationale for enhanced effectiveness of WR1065 and cysteamine as radioprotectors compared to neutral and anionic thiols and suggest that anionic thiols such as GSH should be poor radioprotectors of DNA.