Toxicity of substituted benzaldehydes to photobacterium phosphoreum and quantitative structure‐activity relationship

Acute toxicities (15min‐EC₅₀) of 21 substituted benzaldehydes to Photobacterium phosphoreum were determined. A quantitative structure‐activity relationship (QSAR) was developed using molecular connectivity indices and quantum chemical parameters, which show that the toxicity is influenced mainly by the difference of the simple and valence‐corrected fourth path molecular connectivity, polarizability, dipole moment, and the most negative net atomic charge on an atom. This study further shows that benzaldehydes are reactive chemicals, which exhibit bioreactive toxicity.     

Effects of the Ellagic acid on the N‐Acetyltransferase activity and Acetylation of 2‐aminofluorene in the rat

The effects of the ellagic acid on the in vitro and in vivo acetylation of 2‐aminofluorene were investigated in male Sprague‐Dawley rats. For in vitro examination, cytosols with or without ellagic acid co‐treatment showed different percentage of 2‐aminofluorene acetylation. For in vivo examination, pre‐treatment of male rats with ellagic acid (10 mg/kg) 24h prior to the administration of 2‐aminofluorene (50 mg/kg) resulted in a 26% and 29%, respectively, decrease in the urinary and fecal recovery of N‐acetyl‐2‐aminofluorene, and a 37% decrease in the metabolic clearance of 2‐aminofluorene to N‐acetyl‐2‐aminofluorene. This is the first demonstration that ellagic acid decrease the N‐acetylation of carcinogens in vitro and in vivo.     

Quantitative structure–activity relationship methods for the prediction of the toxicity of pollutants

Environmental Chemistry Letters - Continuous flow of toxic and persistent compounds to the environment is a global health issue. However, assessing the toxic effects of compounds...     

Mutagenic activity of transition‐metal complexes: Relation structure‐mutagenic and antibacterial activity for some Pd(II), Pt(II) and Rh(I) complexes†

The inhibitory and mutagenic action of some Pd(II), Pt(II) and Rh(I) complexes towards various bacterial strains has been evaluated, and some correlations have been found between the chemical behaviour of the complexes and their selective biological activity: most of the complexes cause only a DNA damage repaired by the excision repair system. Particularly, the Rh(I) complexes used in this work show selective antibacterial effects on defective but no effect on wild‐type strains.     

New O,O‐dimethyl (2,2,2‐trichloro‐1‐carbamoyloxy)‐ethyl phosphonates and their biological activity

A series of fifteen carbamoyl derivatives of O,O‐dimethyl (2,2,2‐trichloro‐l‐hydroxy) ethyl phosphonate (trichlorphon) was synthesized. A number of them showed higher insecticidal activity, having at the same time lower toxicity than the starting biologically active structure. A waste‐free technology for the production of the more promising representatives of this series could possibly be developed in the future.     

Alkylation of metals and the activity of metal‐alkyls†

The biochemical basis for resistance to metal ion toxicity is emerging though it is complicated by the different resistance mechanisms. Several strategies for resistance to toxic metal ions have been identified:

1. The development of energy driven efflux pumps which keep toxic element levels low in the interior of the cell. Such mechanisms have been described for Cd(II) and As(V).

2. Oxidation (e.g. AsO^2‐ to AsO₄ ^3‐) or reduction (e.g. Hg²⁺ to Hg⁰) can enzymatically and intracellularly convert a more toxic form of an element to a less toxic form.

3. The biosynthesis of intracellular polymers which serve as traps for the removal of metal ions from solution such as traps have been described for cadmium, calcium, nickel and copper.

4. The binding of metal ions to cell surfaces.

5. The precipitation of insoluble metal complexes (e.g. metal sulfides and metal oxides) at cell surfaces.

6. Biomethylation and transport through cell‐membranes by diffusion controlled processes.

In this short review I shall discuss the implications of biomethylation as a detoxification mechanism for microorganisms as well as for certain higher organisms.     

The relation between chemical structure and mutagenic activity of some polycyclic aromatic sulfur heterocycles (s‐pah)

Results of Hückel Molecular Orbital (HMO) calculations strongly suggest identical metabolic activation routes for the mutagen benzo[2,3]phenanthro[4,5‐bcd]thiophene and its homocyclic parent, benzo[a]pyrene.     

Quantitative structure‐activity relationships of hydrophobic organic chemicals 1

Quantitative structure‐activity relationships of hydrophobic organic chemicals were studied based on equations we established. Results showed that observed toxicity of hydrophobic organic chemicals were correlated to two physical‐chemical parameters: reaction equilibrium constant of target molecule‐organic chemical; octanol/water partition coefficient. Regression results showed that the molecular connectivity index of first‐order was an ideal parameter instead of the equilibrium constant. Good relationships between toxicity data and the two parameters were found for three aquatic organisms with a wide range of chemicals.     

Comparative quantitative structure–activity relationship (QSAR) study on acute toxicity of triazole fungicides to zebrafish

We employed two-dimensional quantitative structure–activity relationship (2D-QSAR) and hologram QSAR (HQSAR) methods to quantitatively investigate the mechanism and active site of toxicity for Danio rerio exposed to triazole fungicides. Our results showed that 2D-QSAR models constructed using the energy of the lowest unoccupied molecular orbit, the net C atom charges, the octanol–water partition coefficient and the molecular shape factor had higher predictive abilities. HQSAR models containing the fragment distinctions atoms (As), bonds (Bs), chirality (Ch) and donors and acceptors (D&A) had higher reliability. It was found that 2D-QSAR results explaining the toxicity mechanism were consistent with HQSAR. In summary, the hydrophobicity and shape/size of the molecule were the important factors influencing the toxic effect of these chemicals against D. rerio. In addition, electron exchange may occur between these fungicides and the target. The study provided a method to evaluate the environmental risk of chemicals with a similar structure, based on the QSAR models obtained.     

Synthesis and antithyroid activity of 6‐n‐propyl‐5‐arylazo‐2‐thiouracils †

The synthesis of several 6‐n‐propyl‐5‐arylazo‐2‐thiouracil derivatives was achieved. The antithyroid activity of these derivatives has been determined using iodine‐125‐thiocyanate discharge technique in rats, and 6‐n‐propyl‐2‐thiouracil (PTU) as a standard. None of the 5‐arylazo‐2‐thiouracil analogs showed antithyroid activity as compared to PTU. The structure‐activity relationships (SAR) of position 5 in the PTU molecule and the requirements for better binding to the proposed receptor are discussed.     

The synergistic effects of increasing temperature and CO2 levels on activity capacity and acid–base balance in the spider crab, Hyas araneus

With global climate change, ocean warming and acidification occur concomitantly. In this study, we tested the hypothesis that increasing CO₂ levels affect the acid–base balance and reduce the activity capacity of the Arctic spider crab Hyas araneus, especially at the limits of thermal tolerance. Crabs were acclimated to projected oceanic CO₂ levels for 12 days (today: 380, towards the year 2100: 750 and 1,120 and beyond: 3,000 μatm) and at two temperatures (1 and 4 °C). Effects of these treatments on the righting response (RR) were determined (1) at acclimation temperatures followed by (2) righting when exposed to an additional acute (15 min) heat stress at 12 °C. Prior to (resting) and after the consecutive stresses of combined righting activity and heat exposure, acid–base status and lactate contents were measured in the haemolymph. Under resting conditions, CO₂ caused a decrease in haemolymph pH and an increase in oxygen partial pressure. Despite some buffering via an accumulation of bicarbonate, the extracellular acidosis remained uncompensated at 1 °C, a trend exacerbated when animals were acclimated to 4 °C. The additional combined exposure to activity and heat had only a slight effect on blood gas and acid–base status. Righting activity in all crabs incubated at 1 and 4 °C was unaffected by elevated CO₂ levels or acute heat stress but was significantly reduced when both stressors acted synergistically. This impact was much stronger in the group acclimated at 1 °C where some individuals acclimated to high CO₂ levels stopped responding. Lactate only accumulated in the haemolymph after combined righting and heat stress. In the group acclimated to 1 °C, lactate content was highest under normocapnia and lowest at the highest CO₂ level in line with the finding that RR was largely reduced. In crabs acclimated to 4 °C, the RR was less affected by CO₂ such that activity caused lactate to increase with rising CO₂ levels. In line with the concept of oxygen and capacity limited thermal tolerance, all animals exposed to temperature extremes displayed a reduction in scope for performance, a trend exacerbated by increasing CO₂ levels. Additionally, the differences seen between cold- and warm-acclimated H. araneus after heat stress indicate that a small shift to higher acclimation temperatures also alleviates the response to temperature extremes, indicating a shift in the thermal tolerance window which reduces susceptibility to additional CO₂ exposure.     

Crystallization and X‐ray structure of 3,3’,4‐trichlorobiphenyl (PCB 35)∗

A method for the preparation of single crystals of PCB 35 suitable for single crystal X‐ray structure determination was developed. This method has already been proven suitable for 2,4'‐dichlorobiphenyl and may prove useful for other PCBs or related compounds. The crystals of PCB 35 are orthorhombic, spacegroup P2₁22₁ (a= 10.665(8), 6 = 3.825(3), c= 14.086(9) Å) and the structure was refined to R = 0.094 for 156 unique observed reflections and 43 parameters. Although the crystals were of poor quality, the structure determination unequivocally confirmed the substitution pattern of the biphenyl moiety by Cl atoms inferred previously from spectroscopic methods. The dihedral angle between the planes of the two phenyl rings is 33(2)°.     

Photodecomposition of Isofenphos (O‐ethyl‐O(2‐isopropoxycarbonyl)‐phenyl)‐Isopropylphos‐Phoramidothioate)

Photodecomposition of the organophosphorus insecticide isofenphos (O‐ethyl‐O‐(2‐isopropoxy‐carbonyl)‐phenyl)‐N‐isopropylphosphoremidothioate) has been studied in solution, on glass and soil surfaces. Isofenphos underwent oxidation from P = S to the P = O group and deesterification on irradiation in hexane and methanol. Photoproducts were isolated and identified by spectroscopic methods.     

δ13C and fatty acid composition of mesopelagic fishes in the South China Sea and their influence factors

Study of the ecology of mesopelagic fishes is central for assessing the active biological pump in the ocean, especially in the mesopelagic layers. The use of δ¹³C and fatty acid analysis can help to analysis the ecology of mesopelagic fishes. Here, we analysed the fatty acid composition of mesopelagic fishes from the continental northern slope of the South China Sea (NSSCS) and compared with nearshore SCS fishes and mesopelagic fishes collected from the Southern Ocean. The mesopelagic fishes had unusually high lipids, which resulted in Δδ¹³C values exceeding 1‰, more than the enrichment factor in the food web. The mesopelagic fishes had higher C18:1n-9/C18:1n-7 and C20:1n-9/ C18:1n-7 ratios compared with other fishes in the SCS, which confirmed that plankton were their main dietary source. The mesopelagic fishes from SCS and Southern Ocean had different ratios of C20:5n-3/C22:6n-3 (EPA/DHA), suggesting geographical locations and diet sources had obvious influence on their fatty acid composition. The SCS mesopelagic fishes had higher C20:4n-6/C22:6n-3 (ARA/DHA) and C20:4n-6/C20:5n-3 (ARA/EPA) ratios than mesopelagic fishes in the Southern Ocean, indicating the influence of physical factors on fatty acid composition. Thus, future studies of the fatty acids in mesopelagic fishes should consider both dietary sources and physical environments.     

The effects of developmental lead (Pb) exposure on the expression of the CTGF and TGF-β1 in hippocampus of pups

Pregnant mice were exposed to control (0%), low (0.1%), moderate (0.5%), and high (1%) lead (Pb) acetate in deionized drinking water from the first day of gestation to postnatal day (PND) 21. Pb concentration was determined in blood and the hippocampus at the 7th, 14th, or 21st day of neonatal mice pups. The expression of connective tissue growth factor (CTGF) and TGF-β1 mRNA and protein was also measured in the hippocampus using RT-PCR and immunohistochemistry assays. The expression of CTGF and TGF-β1 mRNA was up-regulated in hippocampus in Pb-exposed groups. These results were further confirmed by immunohistochemistry staining. Data suggest that CTGF and TGF-β1 genes are differentially regulated and are affected by Pb.     

Butterfly effects in mimicry? Combining signal and taste can twist the relationship of Müllerian co-mimics

Müllerian co-mimics are aposematic species that resemble each other; sharing a warning signal is thought to be mutually beneficial for the co-mimics by reducing per capita predation risk. In Batesian mimicry, edible mimics avoid predation by resembling an aposematic model species. The protection of both the model and the mimic is weakened when the mimics are abundant compared to the models. The quasi-Batesian view suggests that defended (Müllerian) co-mimics, when unequal in their defences, could also show a Batesian-like trend of increasing mortality with increasing abundance of a less defended “mimic”. We manipulated frequencies of unequally distasteful artificial co-mimics that were prey for great tits. The co-mimics had different signals (imperfect mimicry) but were equally preferred by the birds when palatable. Unexpectedly, when unpalatable, one of the signals was easier for the birds to learn to avoid. Consequently, during predator learning, the signal design of the prey strongly affected mortality of the co-mimics; there was an interaction between the signal and frequency treatments, but increasing the frequency of a less defended “mimic” did not increase co-mimic mortalities as predicted. In contrast, in a memory test that followed, the effect of signal design disappeared; if the birds had experienced high frequency of “mimics” during learning, co-mimic mortalities did subsequently increase. Since the effect of co-mimic frequencies on mortalities changed depending on the signal design of the prey and predator experience, the results suggest that mimetic relationship may be an unpredictable interplay of several factors in addition to taste and abundance.     

Synthesis,separation and structure determination of 2,3,3'‐trichlorobiphenyl (PCB 20)† and 3,3’,4‐trichlorobiphenyl (PCB35)†

The combined synthesis and spectrometric characterization of 2,3,3'‐trichlorobiphenyl (PCB 20) and 3,3’,4‐trichlorobiphenyl (PCB 35) is described for the first time. By a combination of highly efficient column distillation and repeated recrystallizations it was possible to isolate the two products as reference materials with a purity exceeding 99%. X‐ray analysis of crystals of 2,3,3'‐trichlorobiphenyl positively identified the substitution pattern of the biphenyl moiety by chlorine atoms. The two phenyl rings are at an angle of 52°, while the relative disposition of the chlorine atoms on both rings is closer to anti than to syn.     

Voltammetric study on the interaction of the heavy metals Cd(II) and Mn(II) with transfer‐RNA,DNA and other polynucleotides

Small amounts of bivalent cations, usually provided by Mg²⁺, are in the living cell necessary for the biological activity of t‐RNA as these bivalent cations influence the tertiary and secondary structure of this globular polynucleotide.

In context with the discussed possibility of carcinogenic actions of ingested Cd it is of particular interest to check whether there exist specific strong interactions of this toxic heavy metal with nucleic acids.

Therefore, the binding of the toxic heavy metal ion Cd²⁺ and the essential heavy metal ion Mn²⁺ to t‐RNA and for comparison to DNA and the polynucleotides poly‐U, poly‐A and poly‐A‐poly‐U has been studied. Free metal ion concentrations have been determined by differential pulse polararography. Association constants and the number of binding sites have been evaluated by the Scatchard method and alternatively according to a simple electrostatic model of the polyelectrolytes. With the Scatchard method for t‐RNA and all polynucleotides with helical structure two different binding sites of different strength are observed. Those with higher association constants are assigned to the helical parts of t‐RNA. Interaction sites with low association constants correspond to the parts with no ordered tertiary structure, as their exclusive occurrence for poly‐U, having a completely stochastic coil structure, reflects. The values of the association constants for the stronger and weaker association sites are in the respective polynucleotides for both investigated bivalent metal ions of comparable magnitude. This emphasizes that the interaction is essentially of electrostatic nature and depends primarily on the charge of the interacting species.

Thus the specific strong interaction of Cd by the intercalation into the tertiary structure of nucleic acids or by chelation of their base units can be ruled out as one possibility for carcinogenity of Cd.

Moreover, under physiological conditions the high excess of competitive Mg²⁺ will suppress the interaction of Cd based on electrostatic forces.     

Potentiometric studies of mixed complexes of cobalt(II) and copper(II) with l‐Asparagine and adenine

A potentiometric titration technique has been used to determine the stability constants for the various complexes of Co(II) and Cu(II) with L‐asparagine and from DNA base, e.g. adenine. Stability constants of ternary systems have been evaluated by the method suggested by Irwing‐Rossotti. In addition, the conditional constants were calculated as a function of pH. The maximum values of the conditional formation constants were found to be in accordance with the mixed‐ligand complex formation constants in a determined pH region. Furthermore, the molar fractions of different species from mixed complexes were calculated by means of formation constants. The values of stability constants of mixed‐ligand complexes at 25°C are as follows: log K= 5.25 for Co(II)‐L‐asparagine‐adenine; log K= 9.30 for Cu(II)‐L‐asparagine‐adenine. The ionic strength was kept constant at I = 0.20 with NaClO₄.     

Concentration profiles of various toxic and non‐toxic elements in sized coal fly ashes from coals of the León basin

The concentration levels of major (Al, Ca, Fe, K, Mg, Mn, Na, Si, Ti) and some trace (Be, Se, Tl) elements were determined by atomic absorption spectrometry for the coal fly ashes emitted in the combustion of anthracite and soft coals. Total contents and concentration profiles were established for all elements studied as a function of the mean particle size. The content of those elements volatilized during coal combustion (Se, Tl) decreases with increasing particle size, while the unvolatilized elements show small changes in their concentration profiles. The content of aluminium shows a minimum level at a mean particle size of about 25 μm.