Lifetime Heterogeneity of DNA-Bound dppz Complexes Originates from Distinct Intercalation Geometries Determined by Complex-Complex Interactions
Artikel i vetenskaplig tidskrift, 2013

Despite the extensive interest in structurally explaining the photophysics of DNA-bound [Ru(phen)(2)dppz](2+) and [Ru(bpy)(2)dppz](2+), the origin of the two distinct emission lifetimes of the pure enantiomers when intercalated into DNA has remained elusive. In this report, we have combined a photophysical characterization with a detailed isothermal titration calorimetry study to investigate the binding of the pure Delta and Lambda enantiomers of both complexes with [poly(dAdT)](2). We find that a binding model with two different binding geometries, proposed to be symmetric and canted intercalation from the minor groove, as recently reported in high-resolution X-ray structures, is required to appropriately explain the data. By assigning the long emission lifetime to the canted binding geometry, we can simultaneously fit both calorimetric data and the binding-density-dependent changes in the relative abundance of the two emission lifetimes using the same binding model. We find that all complex complex interactions are slightly unfavorable for Delta-[Ru(bpy)(2)dppz](2+), whereas interactions involving a complex canted away from a neighbor are favorable for the other three complexes. We also conclude that Delta-[Ru(bpy)(2)dppz](2+) preferably binds isolated, Delta-[Ru(phen)(2)dppz](2+) preferably binds as duplets of canted complexes, and that all complexes are reluctant to form longer consecutive sequences than triplets. We propose that this is due to an interplay of repulsive complex complex and attractive complex-DNA interactions modulated by allosteric DNA conformation changes that are largely affected by the nature of the ancillary ligands.

dichroism

dipyridophenazine complexes

cooperative binding

ligands

one-dimensional lattice

light-switch

linear

minor-groove

d(gtcgac)(2)

excited-state

ruthenium complexes

Författare

Johanna Andersson

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Louise Fornander

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Maria Abrahamsson

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Eimer Tuite

Chalmers University of Technology

Newcastle University

Pär Nordell

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Per Lincoln

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Inorganic Chemistry

0020-1669 (ISSN) 1520-510X (eISSN)

Vol. 52 1151-1159

Ämneskategorier

Kemi

DOI

10.1021/ic302626d