STUDENT RESEaRch SympoSiUm 2010 - Graduate and Research ...

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AbstrActs
when using thin (micrometer) analyte cells, high spatial resolution
levels suitable for capillary flow cells and microfluidic systems,
and remote standoff detection capability. In a typical wave-mixing
optical setup, two input laser beams are focused and mixed inside
the sample to create dynamic gratings. The incoming photons are
then scattered off these gratings to create a signal beam that is
characteristic of the analyte. Since the signal beam is a coherent
laser-like beam, the optical detection efficiency is very high
and the signal-to-noise ratio is excellent. Since the signal beam
has its own propagation direction, one can use effective spatial
filters to minimize optical background noise levels. Wave-mixing
detection sensitivity levels are comparable or better than those
of fluorescence-based methods, and yet, wave mixing can be
used for both fluorescing and non-fluorescing analytes, and many
analytes could be detected in their native form. The wave-mixing
signal has a quadratic dependence on analyte concentration,
and hence, small changes in analyte properties result in more
dramatic changes in the wave-mixing signal.
#192 12:30–2:00
Identification and Quantification of the Biosynthetic Genes
of the Photoactive Siderophore, Vibrioferrin, in the North
Atlantic and its Impact on Algal Iron Acquisition
Lyndsay Trimble, Chemistry (U)
Carl Carrano, Chemistry
Algal-bacterial interactions are a common and important process
in the marine environment. These diverse interactions include
involvement in nutrient exchange, cell differentiation, and algicidal
effects. However, with few exceptions, these interactions are
poorly understood. One particular nutrient element which could be
involved in such interactions is iron, which is important due to its
role in photosynthesis and cellular respiration. Iron, though abundant
in the earth’s crust, is not readily available due to its poor
solubility in the marine environment. Previously it has been shown
that in response to iron limitation, algal-associated heterotrophic
marine bacteria belonging to the Marinobacter genus produce
an iron complexing agent, known as vibrioferrin (VF). Iron-bound
VF undergoes a photochemical reaction that provides a highly
bioavailable form of iron to both the producing bacteria and the
algal partner. In order to assess the importance of VF in mediating
bacterial-algal interactions in the environment, quantitative realtime
PCR (qPCR) has been utilized to identify and quantify the
presence of genes involved in the biosynthesis of VF in the North
Atlantic. These genes are found only in the euphotic zone and
below the deep chlorophyll maxima highlighting the significance
of VF photochemistry and its potential influence on phytoplankton
and bacterial growth.
STUDENT RESEARCH SYMPOSIUM 2010
#193 12:30–2:00
Mechanism of TBP Recruitment to the TATA-less U1
Promoter
Jinjoo Kang, Chemistry & Biochemistry (M)
William Stumph, Chemistry & Biochemistry
Transcription of Drosophila U1 or U6 snRNAs by RNA polymerases
II and III respectively requires a conserved DNA promoter sequence
termed the proximal sequence element A (PSEA), which
is recognized by DmSNAPc, a multi-protein complex. Interestingly,
the RNA polymerase specificity of Drosophila snRNA genes
is determined by only five base pairs differences between the U1
and U6 gene PSEAs. Considerable work in our lab has demonstrated
that DmSNAPc binds to a U1 PSEA in a different conformation
compared to when it binds to U6 PSEA. Further work
suggests that DmSNAPc, when it binds to a U1 PSEA, recruits the
TATA-binding protein (TBP) to the TATA-less U1 promoter. Finally,
we believe that TBP interacts specifically with the PSEB, a second
conserved non-TATA element in the U1 promoter. My work
is designed to gather evidence to support these hypotheses. TBP
was co-overexpressed in Drosophila tissue culture cells together
with the three protein subunits of DmSNAPc. The 6X His –tagged
TBP and DmSNAPc were co-purified by Ni 2+ column affinity
chromatography. When used in a band-shift assay with wild-type
U1 promoter DNA, two shifted bands were observed. Both bands
could be supershifted with antibodies against DmSNAPc, but
only the upper band was supershifted by antibodies against TBP.
No shifted bands were observed with TBP alone in the absence
if DmSNAPc. Because both DmSNAPc and TBP were present in
the upper band, these results suggest that DmSNAPc can recruit
TBP to the U1 promoter. To gain further insight into whether TBP
interacts directly with the PSEB, DNA probes were prepared that
contained either a mutant PSEB or a TATA element replacing the
PSEB. When the PSEB was mutated, the upper TBP-containing
band was significantly decreased. However, the upper band was
increased when the PSEB was changed to a TATA sequence.
These results suggest that TBP may directly interact with the
PSEB. My results indicate that DmSNAPc is involved in the
recruitment of TBP to the TATA-less U1 promoter, and that the
PSEB stabilizes the recruitment of complexes that contain both
DmSNAPc and TBP.