DNA accessibility to minor groove ligands in core nucleosome and chromatosome

Using the circular dichroism spectra induced in the visible by the binding to the minor groove of DNA, we found that Hoechst 33258 is able to occupy i ts specific sites even when these are located inside the nucleosome structu re. This high accessibility of the DNA in the nucleosome is not modified by the removal of the amino-terminal domains of the octamer histones and is n ot reduced by the presence of linker histone, Interesting and reasonable di fferences were found in the association constants.