ja0739436_si_001.pdf (445.69 kB)
Insertion of a Bulky Rhodium Complex into a DNA Cytosine−Cytosine Mismatch: An NMR Solution Study
journal contribution
posted on 2007-10-10, 00:00 authored by Christine Cordier, Valérie C. Pierre, Jacqueline K. BartonThe bulky octahedral complex Rh(bpy)2chrysi3+ (chrysi = 5,6-chrysenequinonediimine) binds
single-base mismatches in a DNA duplex with micromolar binding affinities and high selectivity. Here we
present an NMR solution study to characterize the binding mode of this bulky metal complex with its target
CC mismatch in the oligonucleotide duplex (5‘-CGGACTCCG-3‘)2. Both NOESY and COSY studies indicate
that Rh(bpy)2chrysi3+ inserts deeply in the DNA at the mismatch site via the minor groove and with ejection
of both destabilized cytosines into the opposite major groove. The insertion only minimally distorts the
conformation of the oligonucleotide local to the binding site. Both flanking, well-matched base pairs remain
tightly hydrogen-bonded to each other, and 2D DQF-COSY experiments indicate that all sugars maintain
their original C2‘-endo conformation. Remarkably, 31P NMR reveals that opening of the phosphate angles
from a BI to a BII conformation is sufficient for insertion of the bulky metal complex. These results corroborate
those obtained crystallographically and, importantly, provide structural evidence for this specific insertion
mode in solution.