Science. 2017 Jul 28;357(6349). pii: eaag0025. doi:10.1126/science.aag0025.

Ou HD, Phan S, Deerinck TJ, Thor A, Ellisman MH, O'Shea CC.

ChromEMT: Visualizing 3D chromatin structure and compaction in interphase and mitotic cells.

The membrane-permeable anthraquinone dye DRAQ5 (646/697 nm) was identified by a screen for its capacity to produce singlet oxygen, which polymerises diaminobenzidine (DAB), which binds the electron-dense osmium tetroxide (OsO4). Use of this stain suggests that there are 30 nm fibers may be rare in vivo or an artefact of chromatin purification. The authors suggest that the absence of higher-order fibers helps compaction, because disordered chromatin chains have shorter persistence length.