Extended chromatin fibres: crystallinity, molecular order and reactivity to concanavalin-A

The present study was undertaken to test the reproducible formation of the extended chromatin fibres (ECF), beads and superbeads, and detect molecular order and crystallinity by optical anisotropies in those structures. Chicken erythrocyte smears and mouse liver cell imprints were treated with 2.0-3.0 m NaCl solution in 1% Triton-X100 vertically prior to staining with 0.025% toluidine blue at pH 4. Detection of birefringence and colours of abnormal dispersion of birefringence (ADB) following toluidine blue binding to DNA revealed that the DNA molecular order and crystallinity in decondensed and condensed chromatin are preserved after ECF formation. The tests for Con-A binding to mannose/glucose residues of glycoproteins was confirmed within nuclei, and in the ECF, beads and superbeads. ECF formation was not regular. Clumped cells did not show ECF, although chromatin mobility was observed within the nuclei. Electron microscopy demonstrated that after treatment of nuclei with 0.77 m NaCl ECF always spread from the nuclei, in clumped nuclei the fibres aggregated instead of spreading.