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July 20, 2004
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Eye On Organics
Fluorescence method allows imaging and tracking of chemicals in plant cells |
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STEPHEN K. RITTER |
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Two-photon excitation microscopy (TPEM), a fluorescence technique commonly used to image cell and tissue samples of plants and animals, has been used for the first time to visualize how organic compounds from pesticides or air pollution migrate through the cellular structure of living plants. The researchers who developed the novel application believe that it could help improve the design and use of pesticides, track the migration of chemicals from packaging into food, and design new strategies for bioremediation of contaminated soil.
In TPEM, a laser is used to excite a biological sample with two low-energy photons, which, upon combining at a focal point, have sufficient energy to induce fluorescence without damaging the prepared sample. Fluorescent dyes, green fluorescent protein tags, or other markers typically are needed to highlight specific cell structures. The detected fluorescence in turn can be used to generate an image for further study.
Chemistry Ph.D. student Edward Wild, environmental chemistry professor Kevin C. Jones, and colleagues at the University of Lancaster, in England, came to realize that the natural fluorescence of some cell structures and aromatic organic compounds could be visualized without the need for fluorescence markers [Environ. Sci. Technol., published online June 17, http://dx.doi.org/10.1021/es049915u]. Thus, the researchers are able to nonintrusively analyze plants at the cellular level and track where the compound of interest might degrade or disperse over time.
Using anthracene as a model compound, they developed images that show the chemical as it migrates over a four-day period from the waxy outer surface of corn leaves into the aqueous cytoplasm of epidermal leaf cells. Optical filters allowed the components of the leaves and the anthracene to be visualized as different colors. Anthracene was chosen to be representative of persistent organic pollutants, which before now were believed to partition nearly exclusively into the lipid fraction of vegetation. The Lancaster team’s results have challenged that assumption by showing that organic compounds can migrate into essentially all parts of the leaf structure.
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IN SIGHT A 3-D reconstruction of fluorescence data (top) allows anthracene (blue) to be observed on the surface of a corn leaf, where cell walls and other components are shown in green and chloroplasts are in red. Leaf cross sections (middle) show anthracene initially on the surface, but later migrating into the epidermal cell cytoplasm (bottom).
IMAGES COURTESY OF EDWARD WILD |
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Chemical & Engineering News
ISSN 0009-2347
Copyright © 2004 |
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