[Electron microscopic preparation of DNA on uncharged carbon films (author's transl)]

DNA is adsorbed with densities sufficient for electron microscopy on thin uncharged carbon films. Superhelical SV 40 DNA remains superhelical on the supporting film on the contrary to the relaxation of DNA on films treated with alky dimethylbenzyl ammonium chloride (BAC). The number of superhelical turns increases to the two- or threefold of the value in solution. Investigations with a structural resolution below 1nm are possible with this preparation method.