An Eco- and User-Friendly Herbicide.

The increasing use of pesticides in agriculture and gardening has caused severe deterioration to both the ecosystem and the health of users (human beings), so there is an urgent need for eco- and user-friendly pesticides. Among a variety of herbicides, paraquat (PQ), frequently used as an effective herbicidal agent worldwide, is well-known for its serious toxicity that has killed, and harmed, thousands of people and countless wildlife such as fish. Herein, we present a facile supramolecular formulation of PQ@cucurbit[7]uril (PQ@CB[7]), prepared by simply mixing PQ with equivalent (molar) CB[7] in water. With addition of CB[7], PQ's cellular uptake was dramatically inhibited. The reactive oxygen species (ROS) generation and the associated apoptosis otherwise induced by PQ in cellular models were both reduced, resulting in increased cellular viability. In a wildtype zebrafish model that is a typical fragile wildlife species in the ecosystem, the supramolecular formulation exhibited significantly reduced hepatotoxicity and increased survival rate, in comparison with those of the fish exposed to free PQ. In a mouse model that is clinically relevant to human being, the administration of PQ@CB[7] significantly alleviated major organ injuries and unusual hematological parameters that were otherwise induced by free PQ, resulting in a significantly increased survival rate. Meanwhile, this formulation maintained effective herbicidal activity that was equivalent to that of free PQ. Taken together, this facile supramolecular PQ formulation is providing not only an extremely rare example of an eco- and user-friendly herbicide that has been desired for decades but also a practical solution for green agriculture.

Visible-light hydrogen generation using as photocatalysts layered titanates incorporating in the intergallery space ruthenium tris(bipyridyl) and methyl viologen.

A series of layered titanates containing in the interlayer space tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)(3)(2+)] or methyl viologen (MV(2+)) or both has been prepared and characterized by elemental analyses, XRD, and optical and vibrational spectroscopy. Incorporation of Ru(bpy)(3)(2+) and MV(2+) is confirmed by the increase of the distance between the titanate layers. The presence of Ru(bpy)(3)(2+) in the material is also revealed in optical spectroscopy where the ligand to metal charge transfer band appearing at λ(max) 460 nm is observed. Also incorporation of MV(2+) leads to the observation of the charge transfer complex band with the titanate host from 350 to 650 nm. These solids are active for the photocatalytic hydrogen generation from water when colloidal platinum as catalyst and EDTA as sacrificial electron donor are present in the solution. The maximum efficiency was obtained for a solid consisting of layered titanate containing a 10.2 wt.% loading of Ru(bpy)(3)(2+) incorporated in the titanate layers and MV(2+) and Pt nanoparticles in the aqueous solution. This heterogeneous system produced about one-half the hydrogen generated for the conventional homogeneous system where all the components [Ru(bpy)(3)(2+), MV(2+), Pt, and EDTA] are in solution, with the advantage that it can be used as film or recovered by filtration from the aqueous medium.

Tuneable pseudorotaxane formation between a biotin-avidin bioconjugate and CBPQT4+.

A biotinylated 1,5-dialkoxynaphthalene derivative has been shown to have the ability to bind strongly to avidin and thus act as an artificial binding site for cyclobis(paraquat-p-phenylene) thereby facilitating the formation of a tuneable pseudorotaxane-based bioconjugate.

Template effect of tetrathiafulvalene in the formation of cyclobis(paraquat-p-phenylene).

[reaction: see text] The template effect exerted by tetrathiafulvalene (TTF) in the ring-closure reaction of the trication 5(3+) yielding cyclobis(paraquat-p-phenylene) has been quantitatively evaluated in acetonitrile at 62 degrees C with UV-vis spectrophotometry. The rate of ring closure of the trication 5(3+) largely increases in the presence of the template (a maximum increase of ca. 80 times at [TTF] approximately 0.14 M). The results are compared with those of other aromatic templates, 2 and 3, that were provided with polyethereal sidearms and indicate that the template ability of tetrathiafulvalene is comparable or better than that of the others.

A survey of actinic keratoses among paraquat production workers and a nonexposed friend reference group.

Follow-up on two reports of an excess of keratoses among paraquat production workers was conducted to evaluate the contribution of occupational exposures to the prevalence of keratoses among workers in a paraquat production plant in Texas. A cross-sectional study design was used to compare the prevalence of keratoses among current workers to an age, race, and sex frequency-matched group of their friends who had never worked at the plant. The analysis is based on 112 workers and 232 friends. Exposure, outcome, and covariables used in the analyses were obtained from an interview questionnaire, dermatology exam, and company records. Overall, the prevalence proportion of the presence of any actinic keratoses among workers and friends was similar (0.30 and 0.28, respectively). Among high cumulative exposed workers, the prevalence of any actinic keratoses was 0.40 compared to 0.20 among low-exposed workers and 0.28 among friends. These results were further explored using a multiple logistic regression approach to adjust for known risk and possibly confounding variables. Statistically significant high risks of actinic keratoses were demonstrated for freckling before age 16 years, older age, suntanning behaviors, occupational exposure to polycyclic aromatic hydrocarbons (PAH), and Fitzpatrick skin type. There was no significant contribution of overall exposure status (worker vs. friend). Similar to the crude analysis, the odds of actinic keratoses of high-exposed workers compared to friends was 1.9 (confidence interval [CI] = 0.9-4.2) whereas the comparable odds ratio for low-exposed workers vs. friends was 0.6 (CI = 0.2-1.7). These data do not demonstrate an excess of actinic keratoses overall nor any consistent increase in the odds of keratoses with an increase in plant exposure level.

The genotoxicity of the waste water discharged from paraquat manufacturing and its pyridyl components.

The genotoxic potencies of waste water condensate from paraquat manufacturing and its pyridyl components on V79 cells were evaluated using the alkaline elution assay and 6-thioguanine resistance mutation assay. Although 2,2'-dipyridyl and 2,2',2"-tripyridyl both were highly cytotoxic to the cells, only 2,2'-dipyridyl induced moderate DNA-cleaving activity and a low frequency of thioguanine resistance mutation in V79 cells. However, equally toxic doses of waste water condensate exhibited highly DNA-damaging and mutagenic activities in the same cell system. After chelation of ferrous ions, the number of DNA lesions and frequency of 6-TGr mutations induced by waste water condensate were slightly suppressed, whereas by contrast those induced by 2,2'-dipyridyl were significantly potentiated. These results indicate that the coordination compound formation of pyridyl derivatives of waste water with metal ions, especially ferrous ions, in biological systems may be closely related to these genotoxic mechanisms. Finally, it was found that DMSO (a scavenger of hydroxyl radical) and catalase could remarkably protect cells from genotoxic damage induced by waste water condensate, 2,2'-dipyridyl and their ferrous complexes, but this protection was not observed in cells which were treated with SOD (superoxide dismutase). This suggests that the generation of some unknown active oxygen species may be involved in the genotoxic mechanisms of waste water condensate and its constituent 2,2'-dipyridyl.

Occupational exposure to 4,4'-bipyridyl vapor and aerosol during paraquat manufacturing.

The mass concentrations of both vapor and aerosol phases of 4,4'-bipyridyl were determined by a glass fiber filter and an XAD-2 tube in a paraquat factory. The size distributions of 4,4'-bipyridyl aerosols and particles < 10 microns were measured by a six-stage cascade impactor. The mass concentrations of 4,4'-bipyridyl aerosols were in the range of 81.9 to 159.9 mg/m3 with an average 4,4'-bipyridyl vapor mass concentration of 3.1 mg/m3 at the top of the open tank. On the average, the mass ratio of vapor phase to aerosol phase of 4,4'-bipyridyl was 0.025. Therefore, the aerosol phase is the major form of 4,4'-bipyridyl exposure to the workers in this environment. From the 4,4'-bipyridyl concentrations measured by the sampling systems of an XAD-2 tube alone and a filter followed by an XAD-2 tube, the 4,4'-bipyridyl aerosol collection efficiency of the XAD-2 tube was found to be approximately 50%. The average mass concentrations of less than 10 microns aerosols and 4,4'-bipyridyl aerosol in the occupational environment were 0.42 mg/m3 and 1.26 micrograms/m3, respectively. The mass median aerodynamic diameter (geometric standard deviation) of particles < 10 microns and 4,4'-bipyridyl aerosol are 3.50 microns (2.35) and 3.47 microns (2.58), respectively. The major mass fraction of 4,4'-bipyridyl aerosol occurred in the 3.3-5.8 microns size range. The enclosure efficiencies of a hood cover attached to a suction tube were found to be 88% and 82% for both aerosol and vapor phases of 4,4'-bipyridyl, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

The importance of electrostatic interactions in the binding of paraquat to its elicited monoclonal antibody.

In this study the pH-dependent interactions interactions between a paraquat-specific murine monoclonal antibody and two antigens: paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride), and a p-nitrophenol analogue (1-(N-methyl-4,4'-bipyridinium)-1-(2-hydroxy-5-nitrophenyl)methane dichloride; PQNP) were determined by ELISA. In each case the KAS-pH profile reflected the titration of a single amino acid residue. pK'a values derived from these plots were 8.90 (paraquat) and 8.13 (PQNP). Increasing pH led to a significant increase in the association constant for each antibody complex. A spectrophotometric titration of PQNP in the presence and absence of excess antibody indicated the presence of another charged amino acid residue at the binding site, which could be assigned as a carboxylic acid. From these studies, a model for paraquat-antibody binding has been proposed.