Ultraviolet-induced detection of halogenated pyrimidines (UVID)

When halogenated pyrimidines such as BrdU are used to identify DNA-synthesizing cells, their detection with monoclonal antibodies requires DNA denaturation, which can lead to loss of cells and/or cell markers or antigens. The authors present an alternative method employing ultraviolet light to partially photolyze BrdU and induce extensive damage in the nuclei which have incorporated the pyrimidine. Under appropriate conditions the BrdU in the unfolding chromatin is detected by certain monoclonal antibodies. Since no denaturation step or enzymatic treatment is required, this method preserves cellular markers and avoids enzyme-specific artifacts. Directions are given for both coagulative (ethanol) and crosslinking (formaldehyde) fixation.