gfp: research presentation portugal research.pdf · z (cis) form = fluorescent e (trans) form =...
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GFP: Research Presentation
Anthony Baldridge
Georgia Institute of Technology
Laren Tolbert Group
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What is GFP?First noted in 1955
Found in multiple organisms but cloned from Aequorea victoria
Protein of 238 amino acids
Chromophore formed by intramolecularautocatalytic cyclization
Resulting chromophore responsible for the green fluorescence
Photos: http://www.rpc.msoe.eduhttp://chemistry.nrl.navy.mil
http://technovelgy.com
Used extensively in biology
Protein/protein interactions
Cell studies
Advantages
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What is the GFP chromophore?
Photo: http://www.rpc.msoe.edu
NN
O
H O
Wild-type GFP (wt-GFP)Absorptions: 398 nm and 477 nm
Fluorescence Emission: 508 nm
Quantum yield: 0.79
p-HBDIAbsorption: 370 nm
Fluorescence Emission: 440 nm
Quantum Yield: 0.0001
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Why the gap in Φ?
Z (cis) form = fluorescent
E (trans) form = non-fluorescent
Excited-state cis/trans isomerizationMain non-radiative decay pathway
Ultrafast (<1 ps) deactivation to recover ground state.
Internal conversion faster than fluorescence and low quantum yield is observed.
NN
O
H O N
N
H O O
hv
Z (cis) E (trans)
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Restricting conformational freedom
By restricting conformational freedom then Φ should increase.
Blocking main deactivation pathway
Provide a rigid structure
Similar conditions found in β-barrel (wt-GFP).
In addition to rigidity, complexation may produce planar structure.
N NN
O
XN N
N
O
X M +
M +
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Proof of ConceptN N
N
O
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PDI-Metal complex
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PDI-Metal complex
Fluorescence Peak Change at 428 nm as PDI-ZnCl2 Formation
0
200000
400000
600000
800000
1000000
1200000
1400000
0.00E+00 5.00E-01 1.00E+00 1.50E+00 2.00E+00 2.50E+00 3.00E+00 3.50E+00
ZnCl2 Concentration (mM)
Peak
Inte
nsity
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Hula-TwistMechanism of isomerizationunknown.
Derivatives synthesized that maximize interaction with carbonyl of imidazolone.
Preliminary results of excited state twisting.
NN
O
R
H
O
H
NN
O
R
H
O
HN
N
O
R
HO
H
NN
O
R
OH
HNN
O
R
H
OH
OBT-φ
T2-B
HT
OBT-τ
τφ
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Erlenmeyer Synthesis
Most common technique to synthesize imidazolonesfound in literature
Unsuccessful for 2-pyridine derivatives
A r C H O + A cHN C O 2H A c 2O, A cON a
re fluxA r
NO
O
R N H2
E tOH , ref lu xA r
NN
O
Erlenmeyer, E. Justus Liebigs Ann. Chem. 1893, 275, 1-8.
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Imidazolone Coupling Rxn.
Knoevenagel Condensation
First reproducible successful method for 2-pyridine derivatives.
Allows for use of any aromatic aldehyde.Schiff base is difficult to synthesize
CHO
N
N
O
piperidineN
N
O
+R
R
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Combining the two
Combinatorial Approach
Any aromatic aldehyde
Readily can do substitutions
Synthetic Progress
October 2008
8 compounds
July 2009
75 compounds
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CollaborationsProtein Docking
Database Screening
Solid-State Studies
Octa-acid Encapsulation
Encapsulation by DNA
Aptamers
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CollaborationsDr. V. Ramamurthy – Miami
Encapsulation of chromophore to mimic protein environment
Dr. Young Tae Chang – Singapore
Screening methods to identify activity of chromophores
Dr. Dipaktar Sen – Simon Frazier
Binding chromophores to RNA Aptamers
Dr. Pance Naumov – Osaka
Solid-state studies of dimerization
Hula-twist studies
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AcknowledgementsDr. Laren Tolbert
Dr. Janusz Kowalik
Dr. Kyril Solntsev
Dr. Arthur J. Ragauskas
CollaboratorsDr. V. Ramamurthy – Miami
Dr. Young Tae Chang – Singapore
Dr. Dipaktar Sen – Simon Frazier
Dr. Pance Naumov – Osaka