Hyperchromic

Hyperchromic is an adjective describing a property of increased color intensity or optical absorption in a sample when stained or exposed to light of a given wavelength. The word derives from the Greek hyper- meaning over and chroma meaning color.

In histology and cytology, hyperchromic is used in the term hyperchromasia, which denotes nuclei that stain more intensely with hematoxylin than normal. Hyperchromasia often reflects increased DNA content or reduced chromatin condensation, and it is a common, though not exclusive, morphological indicator of cellular atypia or malignancy. Technical factors such as fixation, section thickness, and stain quality can influence perceived hyperchromasia, so interpretation requires context.

In spectroscopy and biochemistry, hyperchromic effects refer to increases in absorbance or extinction coefficients under certain conditions. A classic example is the hyperchromic shift observed when double-stranded DNA denatures: base stacking is disrupted and absorbance at 260 nm rises. Hyperchromicity also appears in studies of ligand binding and conformational changes where the optical properties of a molecule change upon interaction.

The term is sometimes used more broadly to describe rising color intensity in other staining or imaging methods, but its precise meaning depends on the experimental context. Hyperchromia is a related concept in which increased coloration is observed; discussion often centers on distinguishing genuine chromophoric changes from artifacts.