IMAGING BY FLUORESCENCE VIDEOMICROSCOPY OF INDIVIDUAL SINGLE-STRANDED-DNA MOLECULES IN SOLUTION

We demonstrate that the observation by fluorescence video-microscopy o f individual single stranded DNA molecules is now possible owing to th e use of an asymmetric cyanine (YOYO-1) belonging to a new class of fl uorescent dyes complexing the DNA. The fluorescence of labelled DNA pe rsists in denaturing conditions showing that the dye does not attach s imply to the possible secondary structures. Furthermore it is stable u nder electrophoresis and enables the imaging of stretched molecules.