DECEMBER 2, 2008--Using a combination of technologies--a scientific digital camera with single photon sensitivity and a total internal reflection microscope (TIRFM)--researchers in Paris, France have proven that EcoRV enzymes can jump and slide along strands of DNA. They hope the discovery will shed light on how site-specific proteins rapidly find very short DNA sequences in order to preserve cellular integrity and protect cells against viral attacks, and lead to better genetics research and grasp of certain genetic disorders.
The research group, led by Dr. Pierre Desbiolles at the Laboratoire Kastler Brossel, CRNS and Université Pierre et Marie Curie, needed high resolution detection because each EcoRV enzyme was tagged with only one of two Cy3 labels and imaging had be undertaken dynamically. So they developed a system based on an Andor Technology iXon860 EMCCD able to detect single detect single photons with a frame rate that allows them to follow the rapidly changing events associated with DNA proof reading and repair.
By acquiring extended time series of individual DNA binding events, the team was able to confirm an earlier suggestion that EcoRV could slide along a DNA strand in order to access areas nearby. However, it was unclear whether EcoRV could also jump along DNA between fragments which are spaced further apart. The clear images obtained with their direct microscopic observation technique allowed the researchers to confirm, for the first time, that long-distance excursions of enzyme on DNA were, indeed, possible.
According to Dr. Desbiolles, "To make this breakthrough, we needed a detection system with an ultra high level of sensitivity. We chose to base it on an Andor Technology iXon860 back-illuminated EMCCD camera because it combined the ability to detect single photons with a frame rate that allowed us to follow the rapidly changing events associated with DNA proof reading and repair."