Single-crystal X-ray structure determinations of the complex between the minor-groove binder distamycin and d(GGCCAATTGG) reveal two 1 : 1 binding modes which differ in the orientation of the drug molecule in the minor groove. The two crystals were grown from different crystallization conditions and found to diffract to and ˚ A, respectively. The structures were refined to completion using SHELXL-93, resulting in a residual R factor of ˚ for the resolution structure (including 46 ˚ water molecules) and for the resolution structure (including 74 water molecules). .
