Crop protection chemicals design

Numerous chemicals important to our well-being contain chlorine atoms. Chemists designing pharma ceuticals and crop-protection chemicals, for example, often add chlorine atoms to the structure in order to modify the potency. The antianxiety agent Valium is an example. 

Molecular Modeling A Tool for Designing Crop Protection Chemicals... 

Application of molecular modeling techniques to the biorational design of selective and environmentally safe crop protection chemicals is addressed. Sulfonylurea herbicides are used as an example to illustrate the kinds of biological information that can be known with modern technologies. An example of selective inhibitor design using computer graphics is presented. 

Because of certain proprietary considerations, a protein other than the ALS enzyme will be used to demonstrate how molecular modeling techniques can be applied to the design of crop protection chemicals. Human serum prealbumin has been used by Blaney, et al (15) to model drug-receptor interactions. Its function is to transport the hormone thyroxin. The binding site for thyroxin will... 

Herbicides have one almost unique characteristic among crop protection chemicals in that they are designed to control pest plants within a crop of plants. This property creates an immediate problem of how to control weeds without damage to the crop. Fortunately, many herbicides can be used to control weeds without damage to the crop, a property described as crop selectivity. The most common reason for crop selectivity is more rapid detoxification of the herbicide by crop plants (7). However, one consequence of crop selectivity is that weed species closely related to the crop can rarely be controlled hence the interest in genetically modified herbicide-tolerant crops. 

A field operator exposure study was designed to accommodate the chemical properties and the use pattern involved in the treatment of potato crops for protection against the Colorado potato beetle. Fifteen farmworkers experienced in the use of tractor-drawn sprayers for application of crop protection materials to crops were selected. All were adult males. To avoid production of a large quantity of treated potato crop prior to registration of the product for sale, the trials were performed on stubble fields after harvest of winter wheat crops in a potato-growing area of southern Ontario. This allowed the use of typical farm spray equipment and a typical duration of exposure for a complete shift of work. 

Analysis of particle size is important in a wide range of industries. When the particles are powders, the information is required for research and development as well as for process quality control. Allen states that two thirds of the 3000 products of Dupont s products were sold as powders and that another fifteen percent contained powders. Whilst figures for other companies may be lower, this illustrates the importance of powders for the chemical process industry. If drops are being considered, the interest usually arises from research and development into sprays from nozzles or from confined two-phase flows. The former can have applications from combustion to crop protection. In two-phase flows, the size of drops can affect momentum, heat and mass transfer. In addition, drop sizes are essential for the design of compact gas/liquid separators. 

Beyond understanding plants/pest insect interactions, chemical ecology can help design more environmentally friendly crop protection methods. The VOCs emitted by plants are key mediators in the search and use of resources by predators and parasitoids (see Chapter 9, particularly Figure 9.4). Indeed, these... 

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