||In eukaryotes, three quarters of the DNA is wrapped around histone proteins, forming a string of nucleosomes. This
organization condenses the DNA considerably, and at the same
time restricts it accessibility for DNA binding proteins.
Conformational dynamics of the nucleosome, like partial release
of the DNA, called nucleosome breathing, plays an important part in regulating this accessibility of the genetic information. To study the wrapping and unwrapping in DNA breathing we followed
the Förster Resonance Energy Transfer of a pair of fluorophores
placed in the nucleosome, in time. We selected a single
nucleosome immobilized on glass from an image acquired by a
scanning confocal microscopy. Data acquisition and analysis
software was developed to record and process time trace of
individual nucleosomes with sub ms resolution. Although we can
now reach the required temporal resolution to resolve nucleosome breathing, we did not observe it. A large fraction of the nucleosomes did not show FRET after surface immobilization suggesting partial disassembly, which prevented statistical analysis of large numbers of nucleosomes.