Metal Binding to Bipyridine-Modified PNA
Substitution of natural nucleobases in PNA oligomers with ligands is a strategy for directing metal ion incorporation to specific locations within a PNA duplex. In this study, we have synthesized PNA oligomers that contain up to three adjacent bipyridine ligands and examined the interaction with Ni{sup 2+} and Cu{sup 2+} of these oligomers and of duplexes formed from them. Variable-temperature UV spectroscopy showed that duplexes containing one terminal pair of bipyridine ligands are more stable upon metal binding than their nonmodified counterparts. While binding of one metal ion to duplexes that contain two adjacent bipyridine pairs makes the duplexes more stable, additional metal ions lower the duplex stability, with electrostatic repulsions being, most likely, an important contributor to the destabilization. UV titrations showed that the presence of several bipyridine ligands in close proximity of each other in PNA oligomers exerts a chelate effect. A supramolecular chelate effect occurs when several bipyridines are brought next to each other by hybridization of PNA duplexes. EPR spectroscopy studies indicate that even when two Cu{sup 2+} ions coordinate to a PNA duplex in which two bipyridine pairs are next to each other, the two metal-ligand complexes that form in the duplex are far enough from each other that the dipolar coupling is very weak. EXAFS and XANES show that the Ni{sup 2+}-bipyridine bond lengths are typical for [Ni(bipy){sub 2}]{sup 2+} and [Ni(bipy){sub 3}]{sup 2+} complexes.
- Research Organization:
- Brookhaven National Laboratory (BNL) National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- AC02-98CH10886
- OSTI ID:
- 930179
- Report Number(s):
- BNL--80840-2008-JA
- Journal Information:
- Inorganic Chemistry, Journal Name: Inorganic Chemistry Vol. 45; ISSN 0020-1669; ISSN INOCAJ
- Country of Publication:
- United States
- Language:
- English
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