DNA polymorphism as an origin of adenine-thymine tract length-dependent threading intercalation rate.
Binuclear ruthenium complexes that bind DNA by threading intercalation have recently been found to exhibit an exceptional kinetic selectivity for long polymeric adenine-thymine (AT) DNA. A series of oligonucleotide hairpin duplexes containing a central tract of 6-44 alternating AT base pairs have here been used to investigate the nature of the recognition mechanism. We find that, above a threshold AT tract length corresponding to one helix turn of B-DNA, a dramatic increase in threading intercalation rate occurs. In contrast, such length dependence is not observed for rates of unthreading. Intercalation by any mechanism that depends on the open end of the hairpin was found not to be important in the series of oligonucleotides used, as verified by including in the study a hairpin duplex cyclized by a copper-catalyzed "click" reaction. Our observations are interpreted in terms of a conformational pre-equilibrium, determined by the length of the AT tract. We finally find that mismatches or loops in the oligonucleotide facilitate the threading process, of interest for the development of mismatch-recognizing probes.
Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-41296 Gothenburg, Sweden. par.nordell@chalmers.se
Pär
P
Nordell
Fredrik
F
Westerlund
Anna
A
Reymer
Afaf H
AH
El-Sagheer
Tom
T
Brown
Bengt
B
Nordén
Per
P
Lincoln
D000225:Adenine / Q000737:chemistry*; D020029:Base Pairing; D003460:Crystallization; D004247:DNA / Q000737:chemistry*; D007364:Intercalating Agents / Q000737:chemistry*; D007700:Kinetics; D008163:Luminescent Measurements / Q000379:methods; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry; D012428:Ruthenium / Q000737:chemistry; D013696:Temperature; D013941:Thymine / Q000737:chemistry*
D007364:Intercalating Agents; D009841:Oligonucleotides; D009942:Organometallic Compounds; D012428:Ruthenium; D004247:DNA; D000225:Adenine; D013941:Thymine