Stepwise binding of a cationic phthalocyanine derivative to an all parallel-stranded tetrameric G-quadruplex DNA.

Interaction between an Ga(III) phthalocyanine (Pc) derivative bearing eight N-methylpyridinium groups at peripheral ß-positions (2,3,6,7,10,11,14,15-octakis-[N-methyl-(4-methylpyridinium-3-yloxy)phthalocyaninato] chloro gallium(III) iodide (GaPc)) and an all parallel-stranded tetrameric G-quadruplex formed from a heptanucleotide d(TTAGGGT) ([d(TTAGGGT)]4) has been investigated to elucidate the molecular recognition of G-quadruplex DNA by the Pc derivative, which provides a useful insight as to the design of G-quadruplex ligands suitable for various in vitro and in vivo applications. We found that GaPc binds to the A3G4 and G6T7 steps of [d(TTAGGGT)]4, with binding constants of (21 ± 2) × 106 and (0.09 ± 0.06) × 106 M-1, respectively, to form a 2:1 complex. Obviously, upon the binding of GaPc to each of the sites, the π-π stacking and electrostatic interactions of the Pc moiety and positively-charged side chains of GaPc with a G-quartet and the negatively-charged phosphate groups in nearby phosphodiester bonds of the DNA, respectively, are major driving forces for the complexation. Considering the similarity in the local structural environment between the A3G4 and G6T7 steps of [d(TTAGGGT)]4, the remarkably large difference in the GaPc-binding affinity between them is most likely accounted for by the effect of the polarity of the GaPc-binding site on the intermolecular electrostatic interaction. This finding provides valuable insights as to the design of Pc derivatives as G-quadruplex ligands.

Chronic exposure to diclofenac induces delayed mandibular defects in medaka (Oryzias latipes) in a sex-dependent manner.

Diclofenac is widely distributed in freshwater environments. To support a robust aquatic risk assessment, medaka (Oryzias latipes) were exposed to diclofenac at sublethal concentrations of 0.608, 2.15, 7.29, 26.5, and 94.8 µg/L (as mean measured concentrations) from fertilized eggs to 90-day posthatch. Except for the induction of mandibular defects, no deleterious effects were observed on hatching success and time to hatching at the embryonic stage, or on posthatch mortality, growth in hatched larvae and juveniles, and no abnormal behavior was observed. After 40-day posthatch, mandibular defects in the fish were observed at a concentration of 7.29 µg/L and above. Cumulatively, a morphological examination showed that 4% of the fish in the 7.29 µg/L treatment, 20% in the 26.5 µg/L treatment, and 38% in the 94.8 µg/L treatment exhibited mandibular defects, and the sex ratio of fish with mandibular defects was skewed toward males. These results suggest that diclofenac affects bone remodeling in the lower jaw of medaka after puberty in a sex-dependent manner. The lowest observed-effect concentration and no observed-effect concentration of diclofenac for mandibular dysmorphism through the partial life cycle exposure of the medaka were 26.5 and 7.29 µg/L, respectively.