Antonio Lorente

Physiologically relevant concentrations of NaCl and KCl increase DNA photocleavage by an N-substituted 9-aminomethylanthracene dye.

This paper describes the synthesis of a new 9-aminomethylanthracene dye N-substituted with a pyridinylpolyamine side chain (4). The effects of NaCl and KCl on anthracene/DNA interactions were then studied, with the goal of simulating the conditions of high ionic strength that a DNA photosensitizer might encounter in the cell nucleus (~150 mM of NaCl and 260 mM of KCl). As exemplified by methylene blue (5), the expected effect of increasing ionic strength is to decrease DNA binding and photocleavage yields. In contrast, the addition of 150 mM of NaCl in combination with 260 mM of KCl to photocleavage reactions containing micromolar concentrations of 4 triggers the conversion of supercoiled, nicked, and linear forms of pUC19 plasmid into a highly degraded band of DNA fragments (350 nm hν, pH 7.0). Circular dichroism spectra point to a correlation between salt-induced unwinding of the DNA helix and the increase in DNA photocleavage yields. The results of circular dichroism, UV-vis absorption, fluorescence emission, thermal denaturation, and photocleavage inhibition experiments suggest that the combination of salts causes a change in the DNA binding mode of 4 from intercalation to an external interaction. This in turn leads to an increase in the anthracene-sensitized production of DNA-damaging reactive oxygen species.

Syntheses and copper(II)-dependent DNA photocleavage by acridine and anthracene 1,10-phenanthroline conjugate systems

We report the syntheses and characterization of a series of compounds based on 1,10-phenanthroline covalently tethered, at the 2 and 9 positions, to either two benzene, naphthalene, acridine or anthracene chromophores. The acridine and anthracene derivatives are shown to efficiently cleave pUC19 plasmid DNA upon irradiation with ultraviolet light (pH = 7.0, 22 degrees C, 350 nm). Furthermore, photocleavage levels are markedly increased by the addition of Cu2+ to the DNA photolysis reactions. Interestingly, when the concentrations of the anthracene compounds are lowered from 35 microM to 0.25 microM, the reverse trend is observed. DNA photocleavage is markedly reduced in the presence of copper(II).

Syntheses of imidazole-acridine conjugates as ribonuclease A mimics

Abstract As a result of efforts to mimic the activity of RNase A we report the syntheses of two novel molecules 1 and 2 containing imidazole residues conjugated to an acridine, a well known intercalator and as such these molecules simultaneously have substrate recognition and potential catalytic ability. t-RNA cleavage by 1 and 2 is reported.

Synthesis and stereoselective reductions of chiral β-iminosulfoxides

Abstract Reaction of chiral non racemic β-ketosulfoxides with amines or condensation of the imine enolates with (−)-methyl sulfinate yield optically pure β-iminosulfoxides. The second method requires the presence of an excess of MgBr 2 in order to avoid epimerization at sulfur. The highly diastereoselective reduction of these substrates can be successfully achieved only with DIBAL/ZnBr 2 (d.e.97%). Hydrogenolysis of the CS bond on the obtained β-aminosulfoxides yields the protected with e.e. higher than 97%.

Cyclo-bis-intercalands with acridine subunits linked by rigid spacers

Abstract The tweezer 1 and macrocyclic 2 compounds containing two acridine subunits have been synthesized. A structural study by spectroscopic and molecular mechanics methods is reported. The in vitro cytotoxicity of compounds 1, 2, 4 and 6 has been evaluated.

Synthesis and DNA interaction of ethylenediamine platinum(II) complexes linked to DNA intercalants

A series of ethylenediamine platinum(II) complexes connected through semi-rigid chains of 1,2-bis(4-pyridyl)ethane to DNA intercalating subunits (naphthalene, anthracene or phenazine) has been synthesized, and their interactions with calf thymus (CT) DNA have been evaluated by viscometric titrations and equilibrium dialysis experiments. The parent ligands that contain anthracene or phenazine chromophores showed a monointercalative mode of DNA interaction (especially the anthracene derivative), with apparent association constants in the order of 10(4) M(-1). The corresponding platinum(II) complexes bind CT DNA through bisintercalation, as established by the significant increase of DNA contour length inferred from viscosity measurements, and the association constants are in the order of 10(5) M(-1). The naphthalene derivatives, however, exhibit a mixed mode of interaction, which suggests a partial contribution of both intercalation and groove binding for the ligand, and monointercalation in the case of the platinum(II) complex. Competition dialysis experiments carried out on the intercalative compounds have revealed a moderate selectivity towards GC DNA sequences for the derivatives containing the anthracene chromophore.

DNA photocleavage by dicationic bisintercalants

Abstract The synthesis of new dicationic bisintercalants containing phenazine or naphthalene as photosensitizers and 4,4′-bipyridinium as a linker is reported. Irradiation in the presence of 0.5 μM concentrations of the phenazine intercalants affords cleavage of plasmid DNA (at 22°C, pH 7.0) in good to excellent yields.

Cyclo-bis- and cyclo-tris-intercalands based on acridine subunits

Abstract The macrocyclic receptors 2 and 3 containing proflavine subunits linked by 2,4-hexadiyne spacers have been synthesized. Some physicochemical properties, structural features and cytotoxic activities of these compounds are reported.

Structural and conformational study of 9-(2′-hydroxyethyl)-9-azabicyclo[3.3.1]nonan-3β-ol

Abstract The infrared, 1H and 13C-NMR spectra of 9-(2′-hydroxyethyl)-9-azabicyclo[3.3.1]nonan-3β-ol (I) have been examined in several media. To assist in interpretation of the spectroscopic data, the crystal structure has been determined by X-ray diffraction. The bicyclic system adopts a flattened chair-chair conformation with OH and 2′-hydroxyethyl groups in equatorial and axial position with respect to the piperidinol ring. The crystal structure is stabilized by means of and intermolecular hydrogen bondings. In CDCl3 solution the title compound can be described as an equilibrium between two flattened chair-chair conformations through nitrogen inversion. A slight predominance of the form with the N-substituent axial with respect to the piperidine ring is suggested.

Anthracene and naphthalene (2,2-bipyridine)platinum(II) conjugates: synthesis and DNA photocleavage

Abstract A series of (2,2′-bipyridine)platinum(II) complexes covalently tethered to one or two anthracene or naphthalene chromophores was synthesized in high yields. The compounds were equilibrated with pUC19 plasmid and then irradiated at 350 nm. DNA cleaving reactions showed that the complex attached to two anthracene units exhibited the highest photocleavage efficiency, leading to complete conversion of supercoiled to linear DNA at 0.25 μM concentrations of the complex (37°C, pH 7.4).