AT-dependent luminescence of DNA-threading ruthenium complexes

Journal article, 2007

Whereas the emission from the ruthenium complex Delta Delta-[mu-bidppz(phen)(4)RU2](4+) (P) is five times larger when intercalated into poly(dAdT)(2) than when intercalated into ct-DNA, the homologue Delta Delta-[mu-bidppz(bipy)(4)RU2](4+) (B) has a smaller quantum yield and a red-shifted emission. The origin of this difference is here investigated by studying intercalation into oligonucleotides containing a central AT-tract. Increasing the length of the AT-tract increases the emission quantum yield for P but decreases it for B. However, not even four helix turns of AT base pairs is enough to mimic poly(dAdT)(2). B and P thus use the increased flexibility with increasing length of the AT-tract in opposite ways, whereas B gets more prone to quenching by water, P gets more protected from quenching. The earlier reported gradual increase of the intercalation rate with AT-stretch length is thus paralleled by a gradual change in the equilibrium properties of the intercalated state. (c) 2007 Elsevier B.V. All rights reserved.