Optical Analysis of DNA Coiling and Histone Assembly

Office Of The Director, Nih

Investigators

Abstract

Optical instrumentation has been developed to provide simultaneous transmitted light and fluorescent video images of single chromatin fibers. The chromatin fiber was suspended between attachment to the silanized surface of a square cuvette and a micron-size magnetic bead. A white light source was filtered to provide both excitation light for fluorescent tags attached to the chromatin and non-competing transmission light to monitor the position of the bead. Magnetic tweezers allow manipulation (rotation) of forces applied to the magnetic bead-chromatin complex. This instrumentation allowed real time observation of chaperone-mediated chromatin assembly/disassembly and demonstrated the dynamic equilibrium between assembly and disassembly at the single chromatin fiber level.