Luminescence of ruthenium(II) polypyridyls: evidence for intercalative binding to Z-DNA.
Photophysical studies have been undertaken to characterize the binding interactions of enantiomers of Ru(phen)3(2+), Ru(DIP)3(2+), and racemic Ru(bpy)2dppz2+ (where phen = 1,10-phenanthroline, DIP = 4,7-diphenylphenanthroline, and dppz = dipyridophenazine) with Z-form poly d(GC). Parallel enhancements in steady state luminescent intensity and a lengthening of luminescent lifetimes are seen for ruthenium enantiomers with Z-DNA as for B-DNA but with enantioselectivities reversed. Greater enhancements are seen for delta-isomers with the right-handed helix but for lambda-isomers with the left-handed helix. Ru(bpy)2dppz2+, an avid intercalator in B-DNA, displays no luminescence free in aqueous solution, but luminesces brightly bound to either B- or Z-poly d(GC). Stern-Volmer quenching studies also support the enantioselective preference in binding to B-DNA by delta-isomers and a reversal with binding to Z-DNA preferentially by the lambda-isomers. Steady state polarization studies indicate a rigid association of the complexes with both B- and Z-DNA on the time-scale of their emission and again with symmetrical enantioselectivities for the left and right-handed helices. Given the well characterized intercalative association of the complexes with B-DNA, the parallel results seen here with Z-DNA point strongly to a comparable intercalative association with the Z-form helix. That molecules may interact with Z-DNA through intercalation has not been demonstrated previously and now requires consideration in describing the range of interactions of small molecules and proteins with Z-DNA.
Friedman
A E
AE
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena 91125.
Kumar
C V
CV
Turro
N J
NJ
Barton
J K
JK
D004247:DNA / Q000378:metabolism*; D008163:Luminescent Measurements; D011089:Polydeoxyribonucleotides / Q000138:chemical synthesis / Q000378:metabolism; D012428:Ruthenium / Q000737:chemistry / Q000378:metabolism*
D011089:Polydeoxyribonucleotides; C019530:poly(dC-dG); D012428:Ruthenium; D004247:DNA