electron microscope operating at 75 kV. The width of chromatin fibers was measured from the electron micrographs
negatives using catalase crystal with the lattice spacing
8.75 nm as the standard. For SEM, samples were attached
to coverslips previously coated with 0.1% poly-l lysine.
Samples were fixed and dehydrated as described above,
then critical-point dried and gold coated. Preparations were
examined in a LEO 1450 VP scanning electron microscope.