Practice question

Silica column technology for nucleic acid purification depends on chaotropic salts like guanidinium hydrochloride. At high salt concentration, water molecules are stripped from silica and DNA phosphate backbone, and chaotropic agents disrupt hydrogen bonding networks. This dehydrates silica surface and DNA, allowing formation of cation bridges and hydrogen bonds between negatively charged DNA and silica. At low salt or water, hydration restores and DNA elutes. Binding fails at low salt, high pH alone does not drive adsorption, thus high salt is essential for efficient nucleic acid capture and purification.