DNA-binding fluorochromes: correlation between C-banding of mouse metaphase chromosomes and hydrogen bonding to adenine-thymine base pairs

Numerous non-rigid and bow-shaped cationic fluorochromes exist which bind to chromatin DNA, but only some of them are able to selectively label pericentromeric heterochromatin (C-bands) in metaphase chromosomes. Likewise, some DNA ligands allow the recognition of adenine-thymine sequences establishing hydrogen bonds with acceptor atoms in the minor groove. In the present study, we have employed cationic fluorochromes based on a variety of chemical groups to analyze comparatively their potential to demonstrate C-bands, as well as the relationship between this feature and structural parameters of fluorochromes such as curvature radius and hydrogen-bonding ability. Only fluorochromes that bind DNA by hydrogen bonds demonstrated the characteristic C-banding pattern in mouse metaphase chromosomes (together with a weak G/Q-banding), whereas the other (non-hydrogen-bonding) cationic fluorochromes produced uniform emission without any visible banding.