Figure 1.
(a) Chemical structure of triaminotriazine acridine conjugate (ligand Z1). (b) Overall crystal structure of d[TT(CTG)3AA] complexed to Z1 in an asymmetric unit. Each DNA chain is shown in cartoon representation. Chain A is colored in green, chain B in cyan, chain C in pink and chain D in yellow. (c) Schematic representation of the overall crystal structure. (d) The core of the complex formed by a crossover of all four chains in G5-C6-T7-G8-C9 penta-sequence. (e) Two central stacked G:C pairings form two GC tetrads labeled as GC-I and GC-II. The additional stacked G:C pairing formed by adjacent G8pC9 bases of chains A and C are denoted as GC-III and GC-IV, respectively. The hydrogen bonding between the bases is shown with a black dotted line.
