Nucleosomes are the basic units of eukaryotic chromatin structure. They consist of approx. 150 bp DNA wrapped around a protein core formed by eight histone proteins.
In this highly stable complex the histone subunits hinder binding of other proteins to nucleosomal DNA. Thereby they play an important role in the regulation of all processes that require access to DNA, e.g. transcription and replication. The stability of nucleosomes suggests that elaborate mechanisms must have evolved to guide nucleosome dis- and reassembly and further structural changes. A detailed analysis of nucleosome dynamics is essential for a profound understanding of these processes. We analyse the dynamics of nucleosomes by measuring distances between different points within the nulceosome with Fluorescence Resonance Energy Transfer, a method to measure intramolecular distances. We use nucleosomes that are labeled with fluorescent dyes at specific positions. As a dynamic system nucleosomes adopt different conformations. To avoid averaging over different conformations and to unravel heterogeneities we also analyze these processes on a single-molecule level.
