Atrazine binding studies

Figure 2A. Comparison of data derived from studies of C atrazine binding for thylakoid membranes incubated with 2 /xg of trypsin/mL for various times (0-20 min) with that obtained from direct analysis of electron transport capacity (H2O...

The low-temperature inhibition was further characterized by an extensive study of thylakoid functions. When the light treatment was given at lOQ, the whole-chain (WC) activity was inhibited much more than PSII electron transfer to PPBQ (Fig. 2.a.). At RT, PPBQ-dependent oxygen evolution was slightly more inhibited than WC-activity (Fig. 2. a.). After 2-h treatments at 1500 umol PAR m 2s , the number of atrazine-binding sites had decreased from U.5 nmol atrazine bound per mg chi to U.U at room temperature and to 3.8 at I C. Thus, much faster... 

Antibodies bound by sol-gel encapsulation are used in medicine, immunochro-matography, immunosensors, etc. Immimoglobulins that are trapped retain their ability to bind external antigens from solutions. Antibodie 14D9 catalyze hydrolysis of cyclic acetals, ketals, epoxides, etc. when incorporated in sol-gel matrices. The ability of a sol-gel matrix containing 10% PEG and antiatrazine antibodies to bind atrazine was studied. This matrix recogni2es and binds atrazine and widely distributed herbicides. In this case, neither leaching of antibodies nor nonspecific physical sorption of atrazine on the ceramic matrix occurs. The activity did not decrease... 

Many inhibitors of photoinduced electron transport, including a large number of herbicides, have been shown to bind reversibly and competitively to the protein. The studies volve displacement of a radiolabeled inhibitor, such as [ C]-atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)- -trlazine], by an uy abeled inhibitor (29). Only marginal displacement of [ Cj-atrazine was observed by high concentrations of umbelliferone and naringenin. The other allelochemicals produced no measurable effects. 

Studies on the properties of atzA are relevant for potential applications of this enzyme in removing atrazine from water and soil that require remediation. Atrazine is an effective herbicide, while hydroxyatrazine is nonphytotoxic and binds rapidly to soil. In this context, the first metabolic step carried out by Pseudomonas strain ADP represents the best possible step from an environmental standpoint. While the intact organism catalyzes atrazine hydrolysis and subsequent reactions, the enzyme could prove more efficacious for the following reasons ... 

Kusharyoto W, Pleiss J, Bachmann TT et al. Mapping of a hapten-binding site Molecular modelling and site-directed mutagenesis study of an anti-atrazine antibody. Protein Engineering 2002 15 233-241. 

One additional line of evidence that independently implicates a 32 kDal polypeptide in triazine binding comes from studies on chloroplasts isolated from a maize mutant that specifically lacks the stainable 32 kDal polypeptide and the rapidly labeled 34 kDal polypeptide. Chloroplasts of this PS Il-less lethal mutant lack binding sites for radioactive atrazine (35). 

Only hydroxyatrazine deviates from this pattern in cross reactivity. Because it has the same alkyl structure as atrazine, one would predict a cross reactivity similar to ametryn (about 0.6 ug/L as atrazine). However, hydroxyatrazine gave a response of less than 0.1 ug/L as atrazine. A possible explanation is that the hydroxyl group decreases the binding energy at the specific antibody recognition site. The didealkylatrazine was nonreactive (fig. 2). Neither alachlor nor metolachlor cross reacted with atrazine, which is consistent with results of a previous study (12). 

Studies of purified humic substances are also supportive of the dual-mode concept. Sorption of a PAH apparently depends not only on its hydrophobicity but also on its steric ability to fit into cavities in NOM (13). The abundance and microviscosity of the cavities (23,24) seems to increase with ionic strength, and divalent metal ion concentration. Schulten (25,26) has performed molecular mechanics calculations for a hypothetical humic macromolecule in the presence or absence of water. He found that small molecules—atrazine, pentachlorophenol, a peptide, and a trisaccharide— bind in nanometer-size voids in the humic structure. With continued energy minimization, the voids shrink and become more hindered. 

In order to study the herbicide binding sites and the structure-function relationship of the D protein in photosystem II we have selected different mutants resistant to DCMU, Atrazine and loxynil in a unicellular cyanobacteria Syneohooyst is 6714. We have determined the Dj sequence in each mutant and analyzed by different techniques (fluorescence, oxygen, thermoluminescence) the electron transfer in photosystem II of the different strains. We have also studied the electron transfer in resistant and susceptible Chenoipodium album. 

Mata-Sandoval et al. [32] compared the ability of the rhamnolipid mixture to solubilize the pesticides, trifluralin, coumaphos and atrazine, with the synthetic surfactant Triton X-100. The synthetic surfactant was able to solubihze approximately twice as much of all pesticides as the rhamnolipid. The biosurfactant seems to bind trifluralin tightly in the micelle and releases the pesticide slowly to the aqueous phase, which could have implications for microbial uptake. This approach utilizing micellar solubilization capacities and aqueous-miceUe solubilization rate coefficients and micellar-aqueous transfer rate coefficients could be useful for future studies on microbial uptake. Addition of rhamnohpid in the presence of cadmium enabled biodegradation of the hydrocarbon naphthalene to occur as if no cadmium was present [33]. 

Quantitative Structure Activity Relationships. The goal of our structure activity studies was not the prediction of more active compounds in order to finally get new hints for the development of a herbicide. Instead, we wanted to corroborate our concept that phenols with the appropriate substitution enter the binding niche in the D1 protein just as the classical herbicidal inhibitors like atrazine and diuron do. 

Phospholipase (PLA ) from Vipera russelli and lipase from Rhizopus arrhizus (LRa) were used to obtain almost complete phospholipid (PL) and galactolipid (GL) depletion in the outer monolayer of thylakoid membranes from atrazine-suscepti-ble (S) and -resistant (R) biotypes of Solarium nigrum, PL- and GL-depletion inhibited uncoupled H20/ferricyanide (FeCy) electron flow by 7 and 27%, respectively (not shown). Binding and inhibitory properties of DCMU and atrazine were then studied (Table I). 

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