Poster
Presentation/Preparation
Workshop
Ranjani Muralidharan , April 5 2013
Academic REU GA
CLARITY & SIMPLICITY!
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 Determine the size of the poster
Castle Undergraduate- 36” x 24” & 36”
x 36”
 Make rough draft of layout
 Formatting
Layout
Planning
Other
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TITLE
USF
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INTRODUCTION
RESULTS
AIM
CONCLUSION
EXPERIMENTAL
REFERENCES
Components of an
poster
•
Title
•
Introduction
•
Hypothesis - What is your research question, goal/aim?
•
Methods/Experimental - Explain your methods including
design of your study/chemicals (Flow chart )
•
Results - What were the major findings in your research?
•
Conclusion and future directions
•
References
Figures & graphs
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image
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Figures & Graphs
Seongmin Hong, Xiao Li, Chemistry department, USF
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You need to have a 5 minute version for people
not familiar with technicalities
10 minute version for people in your field
PRACTISE!!!
Dress formal and have a good posture
Poster Rubric
 Topic Coverage
 Organization
 Layout, Design and Graphics
 Sources
 Grammer
 Presentation
EFFECT OF HALIDE IONS ON THE ELECTRO CATALYTIC
ACTIVITY OF Pt Au TOWARDS FORMIC ACID OXIDATION BY SURFACE
ENHANCED RAMAN SPECTROSCOPY WITH POTENTIAL CONTROL.
By Ranjani Muralidharan, Xiao Li
Department of Chemistry, University of South Florida, Tampa, FL
INTRODUCTION
The use of bimetallic catalyst for its ac vity towards
electro oxida on of formic acid has lured lot of
a en on as compared to the pure single catalysts.
There are number of methods of obtaining these
electrode surfaces like electrodeposi on, holding
poten al at certain value and deposi on by applying
a poten al sweep. Spontaneous deposi on is
rela vely simple method, which gives us suitable
coverage and has been widely reported in the last
decade. It has been seen that this method gives
homogenous distribu on of the metal ions on the
surface with
enhanced cataly c ac vity. Thus,
spontaneous deposi on method for obtaining thin
over layers of pla num on transi on metals has been
widely studied for its applica on in the anode of fuel
cells. Especially Pt/Au catalysts are seen to give high
currents for electro oxida on of formic acid and thus
have been promising in their use in the anode of
formic acid fuel cells.
Amount of Electro ac ve pla num
The amount of electroac ve pla num of the Pt/Au surface spontaneously
deposited from PtI62- (green), PtBr42- (red), PtCl62- (blue) electrolyte
precursors.
Poten al Dependant SERS spectra for formic acid electrooxida on on
Pt@Au(15mins) from PtCl62- with 0.45 M HCOOH in 0.125 M HClO4. Excita on
wavelength of 647nm Ar –Kr laser, 35mW.
Electro oxida on of formic acid
Poten al Dependant SERS spectra for formic acid electrooxida on on
Pt@Au(15mins) from PtBr42- with 0.45 M HCOOH in 0.125 M HClO4. Excita on
wavelength of 647nm Ar –Kr laser, 35mW.
ELECTROCHEMICAL RESULTS
Deposi on from 3 precursors
SURFACE ENHANCED RAMAN SPECTROSCOPY
WITH POTENTIAL CONTROL
CV of the electro oxida on of 0.45M HCOOH on Au (poly) (black
line), PtI62- (green), PtBr42- (red), PtCl62- (blue) in 0.125 M HClO4.
Scan rate is 0.05V/s.
Effect of Electrolyte Concentra on
Poten al Dependant SERS spectra for formic acid electrooxida on on
Pt@Au(15mins) from PtI62- with 0.45 M HCOOH in 0.125 M HClO4. Excita on
wavelength of 647nm Ar –Kr laser, 35mW.
The effect of concentra on of the precursor electrolyte employed in the
Deposi on process. PtI62- (green), PtBr42- (red), PtCl62- (blue) .
CONCLUSION FROM ELECTROCHEMICAL
EXPERIMENTS
Cyclic voltammogram of Pt deposited from Au (black dashed line) for
5minutes from PtI62- (green), PtBr42- (red), PtCl62- (blue) in 0.125 M HClO4.
Scan rate is 0.05V/s.
Characteris cs of Pla num deposi on on Au
ü Pla num oxide reduc on peakat 0.31 V for
PtCl62-, 0.37 V for PtBr42- and 0.50 V for PtI62- .
ü Hydrogen/Desorp on on pla num par cles seen
in PtCl62- and PtBr42-.
ü Lowering in the Gold oxide reduc on peak.
§ The oxida on current of formic acid more than
50-60 mes higher than on bare Au surface in
the deposi ons from PtBr42- and PtCl62- .
§ Formic acid oxida on currents obtained from
the three precursor are in the order of PtCl62>PtBr 2- >PtI 2- .
4
6
§ The amount of electrolyte used also affects the
oxida on currents.
CONCLUSION
Ø Spontaneously deposited pla num on gold from
PtBr42- and PtCl62- showed unique high cataly c ac vity
for formic acid electrooxida on in the poten al range of
0.2 - 0.4 V which is cri cal for fuel cell applica ons.
Ø Real me SERS experiments have shown HCOO- as an
intermediate in deposi ons from PtCl62- and PtI62-.
Ø The increased life me of the intermediate can be
linked to the cataly c ac vity of the surface .
LITERATURE CITED
[1] Weaver, M. J. Raman Spectroscopy 2002, 33, 309.
[2]Yoshiki Nagahara, M. H., Soichiro. Y, Junji. I, Shueh-Lin Yau, Kingo. I J. Phys. Chem. B 2004,
108, 3224.
[3] Beltramo, G. L.; Shubina, T. E.; Koper, M. T. M. ChemPhysChem 2005, 6, 2597.
[4] Wang, S.; Kris an, N.; Jiang, S.; Wang, X. Electrochem. Commun. FIELD Full Journal
Title:Electrochemistry Communica ons 2008, 10, 961-964
UNLOCKING THE BINDING AND REACTION MECHANISM OF
HYDROXYUREA AS A BIOLOGICAL NITRIC OXIDE DONOR
Sai Lakshmana Vankayala, Jacqueline C. Hargis, H. Lee Woodcock
Department of Chemistry, University of South Florida, Tampa, FL 33620
METHODS
INTRODUCTION
Hydroxyurea is the only FDA approved treatment of sickle cell
disease. It is believed the primary mechanism of action is associated
with the pharmacological elevation of nitric oxide in the blood,
however, the exact details of this mechanism is still unclear. HU
interacts with oxy and deoxyHb resulting in slow NO production rates.
However, this did not correlate with the observed increase of NO
concentrations in patients undergoing HU therapy. The discrepancy
can be attributed to the interaction of HU competing with other heme
based enzymes such as catalase and peroxidases. In the current
work, we investigate the atomic level details of this process using a
combination of flexible-ligand / flexible-receptor virtual screening (i.e.
induced fit docking, IFD) coupled with energetic analysis that
decomposes interaction energies at the atomic level. Using these
tools we were able to elucidate the previously unknown substrate
binding modes of a series of hydroxyurea analogs to human
hemoglobin, catalase and the concomitant structural changes of the
enzymes. Our results are consistent with kinetic and EPR
measurements of hydroxyurea-hemoglobin reactions and a full
mechanism is proposed that offers new insights into possibly
improving substrate binding and/or reactivity.
RESULTS AND DISCUSSION
G25
G25
V55
A28
N-hydroxyurea (1)
N-hydroxyurea
O-methyl
X=H
radical (2)
N-hydroxyurea (3)
7.54×10-4
±
Mutate flexible active site residues and Glide
SP docking
2.16×10-5
Back mutation and prime minimization
N-methyl
N N -phenyl
N N -n-butyl
N-hydroxyurea (4)
N-hydroxyurea (5)
N-hydroxyurea (6)
3.93×10-2 ± 1.68×10-3
6.24×10-2 ± 6.18 ×10-3
8.56×10-3± 1.87×10-4
N ,N -n-butyl N ,N -methyl
N ,N , N ,N -diethyl
N ,N -4-methoxy phenyl
N-hydroxyurea (6a)
N-hydroxyurea (7)
In-house python script for automation of
flexible dockings
XP descriptor analysis
N-hydroxyurea (8)
2.26×10-3± 8.16×10-5
1.94×10-3± 5.50×10−4
Figure 2. IFD protocol used to predict the binding modes
Figure 1. List of all the hydroxyurea analogs with the
corresponding rate constants in their reaction with OxyHb to
form hydroxyurea nitroxide radicals
b)
a)
PDB 2DN1/1DGG x-ray crystal structures
L105
H58
V62
H58
F46
Od
L110
Ob
Od
L110
Ob
Human
hemoglobin
Human
catalase
Figure 4. IFD structures for predicted binding modes of the
hydroxyurea analogs, 1 and 8 in catalase CpdI shown in pose
A orientation
Figure 3. IFD structures for predicted binding modes of the
hydroxyurea analogs, 7 and 8 in OxyHb are depicted
Direct mechanism
Catalase
Pose A
His-mediated
mechanism
CONCLUSIONS
Figure 5. IFD structures for predicted binding modes of the
hydroxyurea analogs, 1, 7, and 8 in MetHb are depicted
We modeled the first bioactive 3D structure
of OxyHb, MetHb and catalase with Figure 6. IFD structures for predicted binding modes of the hydroxyurea
hydroxyurea
analogues
and
proposed analogs, 1 and 8 in catalase CpdI shown in pose B orientation
reaction
mechanisms
from
mutual
information obtained from binding modes and
biochemical data. IFD results led us to
propose novel mechanisms of action. We
also
highlight
new
insights
into
the
key intermolecular interactions to focus on
when
undertaking
structure
based
substrate/drug design for the effective NO
release. Our work explains the importance of
HN' to hemoglobin and the role active site
residues play in stabilizing bound substrates.
Catalase Pose B : Direct Vs His-mediated mechanism
Work is underway to validate our proposed
mechanisms via QM/MM reaction path
studies.
REFERENCES
Vankayala, S. L.; Hargis, J. C.; Woodcock, H. L.Journal of Chemical Information and Modeling 2012, 52(5),
1288-1297.
Vrcek, I. V.; Sakic, D.; Vrcek, V.; Zipse, H.; Birus, M.Organic & Biomolecular Chemistry2012, 10, 1196-1206.
Huang, J.; Kim-Shapiro, D. B.; King, S. B.Journal of Medicinal Chemistry2004, 47(14), 3495-3501.
Alfonso-Prieto, M.; Vidossich, P.; Rovira, C.Archives of Biochemistry and Biophysics2012, 525(2), 121-130.
Ali, M. E.; Sanyal, B.; Oppeneer, P. M.Journal of Physical Chemistry B2012, 116(20), 5849–5859.
ACKNOWLEDGEMENTS
The authors would like to thank Professor
Wayne Guida, Professor Randy Larsen,
and Dr. Vasiliki Lykourinou for their helpful
discussions.
Acknowledgment
Dr. Richard Pollenz, Professor & Associate Dean, Director
Office For Undergraduate Research
http://www.kumc.edu/SAH/OTEd/jradel/Poster_Presentations
/110.html
Thank You & Questions!