The toxicity to embryo and adult zebrafish (Danio rerio) of Cu complexes with two substituted malonic acids, benzyl‐ and n‐hexadecyl‐, chosen as models for low‐molecular‐weight natural dissolved organic matter, were investigated. Toxicity test solutions at pH 6.5 ± 0.1 with the required Cu speciation were designed using the chemical speciation model MINTEQA2, and the speciation was confirmed by Cu ion‐specific electrode. In the absence of malonic acids, concentrations of Cu2+ up to 1.13 μmol/ L increased the embryo hatching time from approx. 2 d in control solutions (no Cu or malonic acid) and solutions containing malonic acids without Cu to approx. 8 d. The Cu‐benzylmalonic acid complex (n‐octanol/water distribution coefficient [ρow] = 0.00) in the presence of inorganic Cu species did not delay hatching beyond that attributable to Cu2+, In contrast, 0.60 μmol/L Cu‐n‐hexadecylmalonic complexes (ρow = 6.89) delayed hatching by 5.5 d in excess of that attributable to 1.13 μmol/L Cu2+, assuming that the hatching delays caused by the different Cu species were additive, possibly because of Cu entry into the embryo as the lipophilic Cu‐ n‐hexadecylmalonic complex. None of the Cu‐malonic acid complexes was acutely toxic to adult zebrafish at concentrations up to 1.4 μmol/L, possibly because Cu was removed from the Cu‐malonic acid complexes by stronger chelating groups at the gill surface. Substituted malonic acids with similar proton and Cu association constants can be readily prepared with a variety of simple substituents, radiolabeled if required. Our results show that these acids could be useful ligands for investigating intracellular transport and metabolism of metal‐organic complexes.

Abstract-The toxicity to embryo and adult zebrafish (Danio rerio) of Cu complexes with two substituted malonic acids, benzyland n-hexadecyl-, chosen as models for low-molecular-weight natural dissolved organic matter, were investigated. Toxicity test solutions at pH 6.5 Ϯ 0.1 with the required Cu speciation were designed using the chemical speciation model MINTEQA2, and the speciation was confirmed by Cu ion-specific electrode. In the absence of malonic acids, concentrations of Cu 2ϩ up to 1.13 mol/ L increased the embryo hatching time from approx. 2 d in control solutions (no Cu or malonic acid) and solutions containing malonic acids without Cu to approx. 8 d. The Cu-benzylmalonic acid complex (n-octanol/water distribution coefficient [ ow ] ϭ 0.00) in the presence of inorganic Cu species did not delay hatching beyond that attributable to Cu 2ϩ . In contrast, 0.60 mol/L Cu-n-hexadecylmalonic complexes ( ow ϭ 6.89) delayed hatching by 5.5 d in excess of that attributable to 1.13 mol/L Cu 2ϩ , assuming that the hatching delays caused by the different Cu species were additive, possibly because of Cu entry into the embryo as the lipophilic Cu-n-hexadecylmalonic complex. None of the Cu-malonic acid complexes was acutely toxic to adult zebrafish at concentrations up to 1.4 mol/L, possibly because Cu was removed from the Cu-malonic acid complexes by stronger chelating groups at the gill surface. Substituted malonic acids with similar proton and Cu association constants can be readily prepared with a variety of simple substituents, radiolabeled if required. Our results show that these acids could be useful ligands for investigating intracellular transport and metabolism of metal-organic complexes.

The binding of amsacrine [4′-(9-acridinylamino)methanesulfon- m-anisidide] to calf thymus DNA was studied by UV-visible and resonance Raman spectroscopy. A shift of the UV-visible absorption band of amsacrine at 434 to 442 nm together with a decrease in the intensity of this band is observed upon amsacrine-DNA binding. The resonance Raman spectrum of DNA-bound amsacrine shows a general slight decrease in intensity relative to the spectrum of the free species. The significant decrease in intensity of the bands at 1165, 1265, and 1380 cm−1 upon binding to DNA is attributed to the formation of a single amsacrine-DNA species. The assignment of these bands (1165, 1265, and 1380 cm−1), which was based upon a previous normal coordinate analysis (NCA) and molecular neglect of diatomic overlap (MNDO) calculation, and the observed lack of shift in the band positions upon binding are consistent with intercalation being the major binding mode of amsacrine, as inferred previously by other techniques.

Abstract-Toxic metal organic complexes have not been found in natural waters, although some organic acids form bioavailable lipophilic and metabolite-type metal complexes. Landfill leachates usually contain organic acids and in the urban environment these leachates, when mixed with storm waters containing Cu, could be a source of toxic Cu organic complexes in streams and estuaries. We investigated the formation of Cu complexes in the leachate from an active urban landfill and found that some of the complexes formed were toxic to zebrafish embryos. High and low nominal molecular weight (NMWT) fractions; Ͼ5,000 Da and Ͻ700 Da, of leachate both formed Cu complexes with almost identical Cu complexing characteristics but the toxicity was due solely to the low NMWT complexes formed in the Ͻ700 Da fraction. Chemical equilibrium modelling with MINTEQA2 and H and Cu complex conditional association constants and ligand concentrations obtained from pH and Cu titrations with a Cu ion-selective electrode and van den Berg-Ruzic analyses of the titration data was used to calculate the copper speciation in the embryo test solutions. This calculated speciation, which was confirmed by measurements of Cu 2ϩ in the test solutions, enabled the toxicity due to the free Cu ion and to the Cu complexes to be distinguished.

Toxic metal organic complexeshavenot been found in natural waters, although someorganicacids form bioavailable lipophilic and metabolite‐type metal complexes. Landfill leachates usually contain organic acids and in the urban environment these leachates, when mixed with storm waters containing Cu, could be a source of toxic Cu organic complexes in streams and estuaries. We investigated the formation of Cu complexes in the leachate from an active urban landfill and found that some of the complexes formed were toxic to zebrafish embryos. High and low nominal molecular weight (NMWT) fractions; >5,000 Da and <700 Da, of leachate both formed Cu complexes with almost identical Cu complexing characteristics but the toxicity was due solely to the low NMWT complexes formed in the <700 Da fraction. Chemical equilibrium modelling with MINTEQA2 and H and Cu complex conditional association constants and ligand concentrations obtained from pH and Cu titrations with a Cu ion‐selective electrode and van den Berg–Ruzic analyses of the titration data was used to calculate the copper speciation in the embryo test solutions. This calculated speciation, which was confirmed by measurements of Cu2+ in the test solutions, enabled the toxicity due to the free Cu ion and to the Cu complexes to be distinguished.