Since the first structure of the nucleosome was determined 25 years ago, considerable efforts have been made to understand how different chromatin factors engage nucleosomes. Determining X-ray crystal structures of nucleosome-protein complexes proved to be challenging, and fewer than ten such structures have been reported to date. However, after the resolution revolution in single-particle cryogenic electron microscopy (cryo-EM) in 20135, this method has now been used to determine over 40 different nucleosome-protein complex structures. Thus, single-particle cryo-EM has become the method of choice for elucidating structures of nucleosome-protein complexes. Despite this newfound success, it remains a non-trivial task to determine nucleosome-protein complex structures by cryo-EM. A major bottleneck is the preparation of suitable cryo-EM grids of these complexes for data collection. Nucleosome-protein complexes tend to fall apart upon plunge freezing presumably due to particle denaturation at the air-water interface. Indeed, many cryo-EM structures of nucleosome-protein complexes were determined from samples that were chemically crosslinked prior to conventional plunge freezing. A new method was recently described based on the use of graphene-oxide (GO) grids functionalized with negatively charged DNA or synthetic polymers. Here you can see the cryoEM structure determined by using graphene-oxide functionalized grids of the doubly-bound SNF2h-nucleosome complex (PDB code: 8V6V)

#molecularart ... #nucleosome ... #graphene ... #grid ... #functionalization ... #cryoem

Structure rendered with @proteinimaging, post-processed with @stylar and depicted with @corelphotopaint