Cover
: Acridine-4-carboxamide (yellow) intercalated in a novel way into the hexanucleotide d(CGTACG)2 in a complex involving four DNA duplexes. The double intercalation site is formed from a GC base pair overlap of stacked duplexes modified by cytosine exchange with an adjacent double intercalation site in a column of duplexes at 60º. The four interconnected duplexes are each represented in a different colour (green, pink, red and blue). The sodium ion (grey) is at the centre of the figure. The phosphate backbones of the DNA strands are represented as ribbons and the nucleotides and acridine forming one double intercalation site are highlighted by the use of spacefilling atoms. For further details see the paper by Adams et al. in this issue: Nucleic Acids Res. (2000) 28, 4244–4253.[Table of Contents]