Human chromosome structure studied by scanning force microscopy after an enzymatic digestion of the covering cell material

In standard preparations, metaphase human chromosomes are covered by a cell material film composed mainly of proteins and RNA. This film (∼30 nm thickness) hides the chromosome structure to the tip of a scanning force microscope. In this work, a mild enzymatic treatment is applied to remove the cell material film. After treatment, the individual chromatin fibers at the surface were resolved. Furthermore, the chromosome shows a thickness modulation, in which thicker/thinner regions could be associated with G/R bands. Finally, the topography of the chromosomes in solution is presented. The chromosome volume swelled about five-fold and chromatin packaging in bands and coils was observed.