Phenolic herbicides

Then there are a number of pesticides, e.g. the phenolic herbicide dinoseb and the fungicide pentachlorophenol, whose speciation varies strongly in the environmental pH-range. For this reason, one has to consider the pwhen estimating their environmental fate. Structures of the compounds discussed in this section are depicted in Table 1, together with a listing of their pand octanol-water partition coefficients, Kow, of the neutral species (unless otherwise indicated). Typical basic pollutants include the industrial chemicals aniline and jV.jV-dimethylaniline. 

Phenolic ethers, 10 574 Phenolic foundry resins, 18 788-789 Phenolic friction materials, 18 787-788 Phenolic herbicides, 13 293 Phenolic host inclusion compounds, 14 172-174... 

The high toxicities of the nitro phenolic herbicides add to the difficulty of obtaining reliable teratogenicty data and probably account for the paucity of relevant studies in this area. However, studies of the hair dyes--l,2- and 1,4-diaminonitrobenzenes—revealed embryotoxicities and teratogenicities in this series (e.g, cleft palates, intrauterine growth retardation, resorption, blood vessel anomalies, reduced maternal and fetal weights, etc. (ref. 118, abstr. 751 and 752). 

The most frequent use of the photo-Fenton technology has been the treatment of industrial waters and lixiviates. Nitroaromatics, polychlorinated phenols, herbicides (2,4,5-trichlorophenoxyacetic (2,4,5-T), 2,4-dichlorophenoxyacetic acid (2,4-D)) and pesticides have been successfully degraded [39]. 

Herbicides that inhibit photosynthetic electron flow prevent reduction of plastoquinone by the photosystem II acceptor complex. The properties of the photosystem II herbicide receptor proteins have been investigated by binding and displacement studies with radiolabeled herbicides. The herbicide receptor proteins have been identified with herbicide-derived photoaffinity labels. Herbicides, similar in their mode of action to 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) bind to a 34 kDa protein, whereas phenolic herbicides bind to the 43-51 kDa photosystem II reaction center proteins. At these receptor proteins, plastoquinone/herbicide interactions and plastoquinone binding sites have been studied, the latter by means of a plastoquinone-deriv-ed photoaffinity label. For the 34 kDa herbicide binding protein, whose amino acid sequence is known, herbicide and plastoquinone binding are discussed at the molecular level. 

The phenolic photoaffinity label azidodinoseb (Figure 4) binds less specifically than either azidoatrazine or azidotriazinone (14). In addition to other proteins, it labels predominantly the photosystem II reaction center proteins (spinach 43 and 47 kDa Chlamydomo-nas 47 and 51 kDa) (17). Because of the unspecific binding of azidodinoseb, this can best be seen in photosystem II preparations (17). Thus, the phenolic herbicides bind predominantly to the photosystem II reaction center, which might explain many of the differences observed between "DCMU-type" and phenolic herbicides (9). The photosystem II reaction center proteins and the 34 kDa herbicide binding protein must be located closely to and interact with each other in order to explain the mutual displacement of both types of herbicides (8,12,21). Furthermore, it should be noted that for phenolic herbicides, some effects at the donor side of photosystem II (22) and on carotenoid oxidation in the photosystem II reaction center have been found (23). 

PAHs, heterocycles, and phenols in creosotes are quickly destroyed. On the other hand, some of the higher-molecular weight PAHs are only slowly destroyed. Anaerobic conditions enhance the degradation of specific compounds, such as dinoseb (a phenolic herbicide). 

Use Rubber accelerators and antioxidants, dyes and intermediates, photographic chemicals (hydroqui-none), isocyanates for urethane foams, pharmaceuticals, explosives, petroleum refining, diphenyl-amine, phenolics, herbicides, fungicides. 

As already stressed, the mutation Set264 Gly is one which has been observed in nature. It is found by now in all countries and in a variety of weeds which are rendered resistant t ainst triazines and triazinones (see Table 1). It should be noted, that atrazine-resistant rape with a modified Dl protein (Ser264 Gly) is used as a crop in Canada. Resistance against ureas is comparably small and against phenolic herbicides like i-dinoseb, ioxynil and DNOC negative cross resistance is observed. 

Changes in binding affinities for herbicides in the Leu275 Phe mutant are marginal. It should only be stressed that triazinones are rendered resistant in this mutant and supersensitivity is observed against the phenolic herbicide ioxynil. 

The first photosynthesis-inhibiting herbicides such as arylurea (e.g., diuron) and triazines derivatives (e.g., atrazine) were identified in 1956 even before the photosynthetic reactions and two photosystems were known and before plastoquinone had been discovered. Surprisingly, this group of herbicides still dominates the field. The second group, which includes phenolic compounds such as bromoxynil and ioxynil, were recognized later. Although phenolic herbicides inhibit the PS II reaction centre differently from triazine herbicides, they also interfere with the Qg function and bind the DI protein. 

Due to their difference in chemistry, all PSII-inhibiting herbicides demonstrate different binding properties. For example, urea/triazine type inhibitors were proposed to be oriented towards Set 264, triazinones towards Ala 251 and phenolic herbicides were oriented towards His 215 (Table 1). ... 

Dose/response curves were developed from traces such as shown in Figure 3B for dinoseb. For comparative purposes, the concentration of compound required to increase the rate of ferricyanide reduction to twice that of the no-herbicide control rate are shown in the last column of Table VI. Uncouplers such as FCCP accelerate the rate of ferricyanide reduction, presumably by shuttling protons across the membrane in response to the electrical potential generated by the reduction of ferricyanide by ferrocene (28). In this study, FCCP was the most effective compound. The two phenolic herbicides (dinoseb and ioxynil) were more active than propanil and chlorpropham. Among the carbanilates, 3-CHPC and... 

Photoaffinity labels are an efficient tool for identification of inhibitor binding proteins in the photosynthetic electron transport chain. [ H]Azido-dinoseb, an azido-deri-vative of the phenolic herbicide dinoseb, was synthesized almost a decade ago and was shown to bind primarily to a 41 kDa protein (1,2). Contrary, labeling with azido-deri-vates of diuron-type herbicides revealed that these herbicides bind to a 32 kDa protein, which has now been recognized as the D-1 protein of the photosystem II reaction center core complex (see references in (3)). Tyrosine residues in positions 237 and 254 of the D-1 sequence were demonstrated to be the primary target of [ CJazido-monuron (3). The phenolic herbicide [ I]azido-ioxynil also labels predominantly the D-1 protein in position of Val249 and only in trace amounts a 41 kDa protein (4). 

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