Detection of nucleosomal substructures using solid-state nanopores.

Histone proteins assemble onto DNA into nucleosomes that control the structure and function of eukaryotic chromatin. More specifically, the structural integrity of nucleosomes regulates gene expression rates and serves as an important early marker for cell apoptosis. Nucleosomal (sub)structures are however hard to detect and characterize. Here, we show that solid-state nanopores are well suited for fast and label-free detection of nucleosomes and its histone subcomplexes. (Nucleo-)protein complexes are individually driven through the nanopore by an applied electric field, which results in characteristic conductance blockades that provide quantitative information on the molecular size of the translocating complex. We observe a systematic dependence of the conductance blockade and translocation time on the molecular weight of the nucleosomal substructures. This allows discriminating and characterizing these protein and DNA-protein complexes at the single-complex level. Finally, we demonstrate the ability to distinguish nucleosomes and dinucleosomes as a first step toward using the nanopore platform to study chromatin arrays.