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Author
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Maggie
Walser
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Chemical
Engineering
and Chemistry
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Interest
in environmental issues was the motivation behind Maggie Walsers
research pursuits. Her interest in atmospheric chemistry led
to her current study of agricultural emissions of trace gases,
which allowed her to learn and apply aspects of earth science
and biology and gain a variety of new skills. Maggie has taken
on various roles during her undergraduate years, including guiding,
advising and helping fellow students. She has been a University
Studies discussion leader, a House Assistant in Arroyo Vista,
and a Peer Academic Advisor for the School of Physical Sciences.
Her advice to others is Find something you care about
and get involved!
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Abstract
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Inorganic halogen
radicals in the atmosphere play a role in stratospheric ozone
destruction. Methyl halides act as transport vectors for halogen
radicals from surface sources to the atmosphere, making knowledge
of their budgets necessary. Atmospheric concentrations of methyl
halides have been measured, but their fluxes are not yet fully
quantified. Better estimation of methyl halide sources and atmospheric
budgets can be gained from the measurement of emissions from
agricultural and other terrestrial plants. This study sought
an understanding of the metabolic mechanism(s) that produces
methyl halides. The role of methyl transferases in methyl halide
biosynthesis in rice was examined using leaf-disk enzyme inhibition
assays with known methyl transferase substrates as possible
competitive inhibitors. Only thiocyanate had a significant impact
(p < 0.05) on methyl bromide generation, while methyl iodide
synthesis was not significantly inhibited by any of the methyl
transferase substrates surveyed. In all assays, methyl bromide
production was inhibited more than that of methyl iodide, suggesting
that either the enzyme(s) responsible for methyl halide synthesis
binds iodide preferentially, or a suitable competitive substrate
was not found. Methyl halide emissions from barley, corn, soybean,
and wheat leaf disks were also investigated. The findings of
this investigation increase knowledge of the biochemical production
pathway(s) of methyl halides.
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Faculty
Mentor
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Maggie Walsers
research topic was unusually original so we could only guess
what her experiments would show. Methyl bromide is a chemical
that is produced industrially and used as an agricultural and
structural fumigant. Its use is being banned worldwide due to
its potential impact on the ozone layer. The ban was conceived
before natural sources were investigated. We have found that
methyl bromide and methyl iodide are emitted by rice plants,
and our group set out to learn the metabolic mechanism of biochemical
production of methyl halide gases by plants. Maggie used potential
chemical inhibitors to see if they would impede the activity
of methyl halide transferase enzymes in plant leaves. She made
many difficult measurements that were true experiments, and
she found that one of the chemicals inhibited methyl bromide
production and that none of them significantly impeded formation
of methyl iodide. Her research unveiled the complexity of this
new topic.
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If
you wish to view the paper in its entirety, please select
the link given to the PDF file. [Maggie
Walser.pdf]
If you wish to download the Adobe Acrobat Reader,
please go to Adobes website (www.adobe.com).
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