development of water splitting catalysts using a novel ... · development of water splitting...
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Development of Water Splitting Catalysts Using a Novel Molecular
Evolution ApproachNeal Woodbury, Arman Ghodousi, Trent Northen, Matt Greving, Pallav Kumar, Bharath Takulapalli, Nicolas Yakubchak, James Allen, JoAnn
Williams, Trevor Thornton, Stephen Johnston, Zhan-Gong Zhao
The Biodesign Institute at Arizona State University
May 20, 2009
pd_19_woodburyThis presentation does not contain any proprietary, confidential, or otherwise restricted information
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Overview
• Start - July 1, 2005 • Finish - June 30, 2009 • 70% Complete
• Barriers addressed– H. System Efficiency– J. Renewable Integration
• Total Project Funding– DOE - $1,200,000– Contractor - $300,000
• Funding for FY09– $300,000 DOE– $75,000 Contractor
Timeline
Budget
Barriers
• CombiMatrix Corp., Mukilteo, WA
• Prof. Bill Armstrong, Boston College
Partners
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Objectives
• Broad Objectives:Develop a novel approach to creating molecular catalysts for redox reactions based on high throughput synthesis on electrodesMimick Nature’s approach to water splittingReduce the overpotential by 30%
• Specific Objectives (FY09):Optimize high throughput peptide synthesis on CombiMatrix ArraysOptimize the multielectrode measurements of water splitting on the CombiMatrix ArraysDemonstrate several rounds of optimization for catalytic activity
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Significance
• The impact would be an energetically more efficient method for production of hydrogen from renewable electricity sources
• This addresses both System Efficiency and Renewable Integration
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General Approach• Synthesis of 12,000 different
peptides directly on electrodes• Binding of metal ions or metal
complex catalysts to the peptides, mimicking PSII water splitting complex
• Direct electrochemical measurement of current due to electrolysis at each electrode
• Analysis of one library of molecules informs the production of the next library
• Iterative optimization should result in an efficient water splitting catalyst
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Milestones (FY09)
1. Multi-step patterned synthesis of peptides in an array2. Verification of synthesis via direct MALDI spectroscopy
on the surface3. Automation of array synthesis4. Background current measurements on the arrays5. Comparing currents from peptides with and without Mn
on the arrays6. Iterate synthesis and measurement to result in a
sequence optimization
Go/No Go to continue pursuing this approach dependson 1) ability to measure catalytic signal above noise and 2) ability to reproducibly synthesize arrays with multiplevariable residues
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Summary of Past Accomplishments
1. Tested two platforms, light directed on home-builtarrays and electrochemically directed via CombiMatrixarrays: elected CombiMatrix arrays
2. Design, synthesis and characterization of initial Mnbinding peptides
3. Partnership formed with Mn-complex chemist4. Developed MALDI method for measuring products of in
situ synthesis directly on the surface5. Partnered with CombiMatrix to modify sensing
equipment to measure currents at 12,500 electrodes6. Demonstrated ability to perform standard solid phase
synthesis on the arrays (by nonpatterned methods)7. Demonstrated ability to remove blocking groups using
patterned electrochemically generated acids and create peptide bonds
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Accomplishment: Multistep Synthesis
1.Fmoc-Leu-OH, HBTU/HOBt, DMF, DIPEA
Powered
EGA removes Trt from peptide chains over select electrodes
b.Biotin-SRP-Fluorophore
c.Biotin-SRP-HRP
a.Direct MALDI characterization
PL
NH
2
PL
NH
2
PL N
H2
PL N
H2
PL N
H2
PL L
eu-N
HTr
t
PL-L
eu-N
H2
PL-L
eu-N
H2
PL-P
eptid
e A
PL-P
eptid
e B
PL-P
eptid
e C
PL-P
eptid
e D
PL-P
eptid
e E
Ph-NH-NH-Ph
Ph-N=N-Ph + 2H+
-2e-
2. 20% Piperidine in DMF
3. Trt-Cl, DIEA in DMF
PL L
eu-
NH
Trt
PL L
eu-
NH
Trt
PL L
eu-
NH
Trt
PL L
eu-
NH
Trt
PL L
eu-
NH
Trt
PL L
eu-N
HTr
t
PL L
eu-N
HTr
t
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Accomplishment: Synthesis Verification
Peptide with three echem steps
Control region
Peptide with one echem step
Peptide with two echem steps
The major product was a peptide with three of its ten residues patterned by electrochemical synthesis (85% per step yield)
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Accomplishment: Automation
1. Fluidic connection between Pioneer synthesizer and Combimatrix synthesis chamber
2. Software control interface developed between synthesizer and synthesis system
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Accomplishment: Array Current Background
Large, but systematic current variations across electrodes
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Accomplishment: Comparing +/- Mn peptides
No significant difference between Mnbinding peptide and control
Peptide 3c
0
5
10
15
20
25
30
35
40
0 0.5 1 1.5 2 2.5
Potential (V)
Cur
rent
(nA
0 mM Mn10 mM Mn
Peptide 4A
-5
0
5
10
15
20
25
30
35
40
45
0 0.5 1 1.5 2 2.5
Potential (V)
Cur
rent
(nA
0 mM Mn10 mM Mn
Mn binding Peptide Control Peptide
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Milestones (FY09)
1. Multi-step patterned synthesis of peptides in an array
2. Verification of synthesis via direct MALDI spectroscopy on the surface
3. Automation of array synthesis4. Background current measurements on the
arrays5. Comparing currents from peptides with and
without Mn on the arrays6. Iterate synthesis and measurement to result in
a sequence optimization
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Key Additional Finding(Not DOE funded)
Peptide space is smooth and can be searched through iterative mutation
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Key Additional Finding(Not DOE funded)
Peptides can be used to stabilize or modify activity of existing catalysts
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Collaborators
• CombiMatrixo Industry partnero Funded through equipment purchaseo Provides software/hardware development
assistanceo Outside DOE hydrogen program
• Professor William Armstrongo Boston Universityo Currently unfundedo Will provide Mn-complex catalystso Outside DOE hydrogen program
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Future Work
• FY09 is final year of DOE funding (official end June 09, but no cost extension to December granted)
• Perform an Iterative optimization:1. Start with one of our peptides known to
bind Mn2. Select 3-4 residues thought to be key to
catalysis3. Synthesize array with all possible variants4. Measure currents vs. voltage5. Pick best6. Repeat for 3 additional residues7. Etc.
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Summary
• After choosing the electrochemical patterning platform, synthesis was optimized to about 85% yield
• Still limited by issues with side chain reactivity• Using a modified CombiMatrix sensing
instrument, have made electrochemical measurements at 12,500 electrodes
• Current Mn binding peptides do not show high enough catalysis to measure on the electrode arrays
• Goal is not to create an array and attempt and optimization in remaining 8 months
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• Eradicating Cancer• Rapid Vaccine
Discovery System• Defending Against
HIV• Diabetes Detection
and Management
• Preventing Pneumonia in Newborns
• Treating Childhood Mitochondrial Diseases
• Using Nature to Clean Water
• Energy from Waste
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