The crystal structures of the complexes between d (GAAGCTTC)
2 and actinomycin D have been determined in two crystal forms by X-ray diffraction analyses and refined to R-factors of 0.187 (
C2 form) and 0.202 (
F222 form) at 3.0Å resolution, respectively. In each complex, actinomycin D intercalates between the middle 5'- (GC) -3' base pairs from the minor groove site and forms hydrogen bonds and van der Waals contacts with DNA. A molecular modeling study based on the crystal structures and a spectroscopic study of the complex in solution have indicated that actinomycin D may have an affinity for A-DNA than B-DNA in approaching to DNA.
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