Chromatin fluorescence by pyronin staining

Summary Human, chicken and mouse cells from different tissues show a bright red-orange fluorescence of the chromatin after staining with pyronin Y. The possibility that intercalation of the dye into double helical nucleic acids accounts for this fluorescence pattern is briefly discussed.This work was partially supported by a grant from the Comisión Asesora de Investigación Científica y Técnica, Spain.