I have been studying DNA hydroxymethylation and the the reverse reaction using spectroscopy at 280 nm (self build fixed wavelength led instrument). After prolonged incubation the absorption for some reactions is strongly decreased but on adding NaOH there is a large increase in absorption followed by a slow decrease. I attribute this to a rapid destruction of DNA-DNA crosslinks and a slower reversal of methylol adducts respectively. At 280 nm hyperchromicity due to alkaline denaturation of DNA is not significant. Has anyone observed similar effects?

Thanks & Best regards, Mike