Spectroscopic Identification of Binding Modes of Anthracene Probes and DNA Sequence Recognition†

Abstract

The binding properties of two anthracene derivatives with calf thymus DNA (CT DNA), poly(dA-dT), and poly(dG) x poly(dC) are reported. One contained bulky, cyclic cationic substituents at the 9 and 10 positions, and the other carried acylic, branched, cationic substituents. Binding of the probes to the DNA was examined by calorimetry, spectroscopy and helix melting studies. The cyclic derivative indicated exothermic binding, strong hypochromism, bathochromism, positive induced circular dichroism (CD, 300-400 nm), significant unwinding of the helix, large increases in the helix melting temperature, strong but negative linear dichroism (LD, 300-400 nm) and considerable stabilization of the helix. In contrast, the acyclic analog indicated thermoneutral binding, smaller hypochromism, no bathochromism, very weak induced CD, and no change in the helix melting temperature with any of the DNA polymers. A sharp distinction between the binding properties of the two probes is indicated, and both have intrinsic binding constants of approximately 10(6) M(-1) for the three polymers. However, when the ionic strength of the medium was lowered (10 mM NaCl), the absorption as well as CD spectral changes associated with the binding of the acyclic derivative corresponded with those of the cyclic derivative. The acyclic derivative showed large preference (10-fold) for poly(dG) x poly(dC) over poly(dA-dT), whereas the cyclic analog showed no preference. The characteristic spectroscopic signatures of the two distinct binding modes of these probes will be helpful in deciphering the interaction of other anthracene derivatives with DNA.

Pyrazolyl–Diamine Ligands That Bear Anthracenyl Moieties and Their Rhenium(I) Tricarbonyl Complexes: Synthesis, Characterisation and DNA‐Binding Properties

“…The UV/vis spectroscopy data that were collected for L 1 and L 2 indicate that the binding of these probes to CT DNA is more likely to be by intercalation than groove binding because the spectral changes that arise from their interaction with CT DNA are in quite good agreement with the spectroscopic signatures that were assigned recently by Kumar et al [13] These authors found a red shift, an A C H T U N G T R E N N U N G extensive hypochromism and a substantial broadening of the bands of the anthracenyl chromophore in the 300-400 nm region, as a result of the strong electron interaction between the p electrons of the intercalated polyaromatic structure and those of the DNA bases. In particular, the 5-6 nm red shifts of L 1 and L 2 compare well with the values (6-8 nm) that were reported in the literature for other (9-anthrylalkyl)amine derivatives, which are considered to act as DNA intercalators.…”

“…[10][11][12] Moreover, anthracenyl chromophores have a moderate molar absorptivity in the near-UV region and good fluorescence quantum yields; this allows the study of the binding of the ligands and the respective Re complexes with DNA by spectroscopic techniques, as well as the evaluation of their cellular uptake by fluorescence microscopy. [13] …”

“…They were characterised by IR, 1 H and 13 C NMR spectroscopies, as well as by ESI-MS spectrometry. As for the corresponding ligands, we could not obtain satisfactory elemental analysis for 7-9, even though the 1 H and 13 C NMR spectra showed a high bulk purity for these compounds. The ESI-MS analysis showed the expected molecular ions at m/z 643.0 (7 and 9) and 614.9 (8), which confirms the proposed formulation.…”

“…Positive and intense ICD spectra are expected in the 320-400 nm region when the anthracenyl chromophore is intercalated with its long axis aligned to the long axis of the DNA base pairs. [13] The pyrazolyl-diamine derivatives that have the terminal 9-anthrylmethyl substituent, pz*NN-Ant (pz* = pz, L 1 ; 3,5-Me 2 pz, L 2 ) and fac-[Re(CO) 3 {3,5-Me 2 pzNN-Ant}]Br (7), showed relatively intense positive ICD peaks in the 320-400 nm region upon binding to DNA, as shown for L 2 and for the respective Re complex (7) in Figure 5. However, the spectra of These data are consistent with the positive ICD spectra that were recently reported for other amine derivatives of anthracene that have been recognised as DNA intercalators.…”

“…However, the spectra of These data are consistent with the positive ICD spectra that were recently reported for other amine derivatives of anthracene that have been recognised as DNA intercalators. [13,16,23] In contrast, the molecules that contain the anthracenyl chromophore at the 4-position of the pyrazole ring, Ant-pz*NN (pz* = pz, As an example, the ICD spectra that were obtained for L 4 and complex 9 are presented in Figure 5. This behaviour resembles that which was reported recently by Kumar et al for an anthracenyl derivative that bore 2-hydroxyethylamine substituents at the 9-and 10-positions, a compound that has been proposed to be more likely to be bound to DNA through a groove-binding mode.…”