Principal Investigators Prof. Ron Crawford, Team Leader (microbiology)
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Transcript of Principal Investigators Prof. Ron Crawford, Team Leader (microbiology)
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
Principal Investigators• Prof. Ron Crawford, Team Leader (microbiology)
•Dr. Mohammed M. Mojarradi, Team Leader (Jet Propulsion Laboratory)
•Prof. Rick Wells (microelectronics)• Prof. Frank Cheng (chemistry)
• Prof. Chien Wai (chemistry)• Prof. Tony Anderson (mechanical engineering)
Senior Scientists • Dr. Andrzej Paszczynski (staff biochemist)• Dr. Qingyong Lang (postdoctoral chemist)
Students and Staff• Mr. Bruce Barnes (microelectronics Ph.D. candidate)
• Ms. Lisa Allenbach (technical assistant)• Mr. Dan Erwin (undergraduate researcher)
Funding received from NASA/JPL on 11/30/99
Research Team
Describing and Measuring Chemical Signatures of Life
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
• The Goal:
To develop a suite of prototype devices that together will indicate the presence or absence of life beyond Earth.
• Assumptions:
Life requires continual energy input, tapped in a controlled manner. - Metabolism
Form of energy: Chemical energy
The life forms we are seeking are living entities, not fossils.
El
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
Electron Donors - Reducing Agents
Electron Acceptors - Oxidizing Agents
e-
•H2, NH3/NH4+, CH4, H2S
•Metal ions (Fe2+), Metals
•Hydrocarbons
•O2, NO3-, SO2/SO3
•Metal Ions (Fe3+ and higher)
Energy
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
Respiratory Chain
(CH2O)n - 0.70 voltse-
NAD+ + H+ + 2e- NADH -0.32 volts
e-
FMN + 2H+ + 2e- FMNH2 -0.30 Ve-
FAD + 2H+ + 2e- FADH2 -0.22 V
e-
CoQ + 2H+ + 2e- CoQH2 0.04 V
e-
Cytochrome b (3+) e- Cytochrome b (2+) 0.07 V
Cytochrome c1 (3+) e- Cytochrome c1 (2+) 0.023 V
Cytochrome c (3+) e- Cytochrome c (2+) 0.025 V
e-
e-
Cytochrome a (3+) e- Cytochrome a (2+) 0.029 Ve-
Cytochrome a3 (3+) e- Cytochrome a3 (2+) 0.055 Ve-
e-
O2 + 4H+ + 4e- 2H2O +0.77 volts
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
waterfall Vs. series of dams
Water
flow
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
Waterfall vs. Dams
•Regulation of water flow metabolism
•Control of energy utilization
•More efficient utilization of energy
•Storage of energy
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
•Electron transport agents range from –1.0 to +1.0 volt
•In order to transport electrical current, agents must be able to undergo several reduction-oxidation (redox) cycles.
Ox + ne- Red
•Electrochemical properties - reversible, quasi-reversible
•Detectable by voltammetric methods
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
Sample Extraction Module
Compound Separation Module
Detection Module
Data Processing Module
•Sample will be obtained and life signature compounds (redox agents) extracted by either a chemical solvent or supercritical CO2
•Extracted compounds will be separated, probably by capillary electrophoresis (CE).
•Components separated in the previous module will be detected here using voltammetric, spectral absorbance detectors, and MS/MS.
•Data will be transmitted to Earth for processing.
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
Biological samples for validating methods
Pure cultures of representative soil bacteria
• Pseudomonas stutzeri (gram negative, facultative)
• Arthrobacter (gram positive, aerobic)
• Bacillus (gram positive, facultative, endospores)
Sand containing various numbers of these bacteria
Real soils known to contain few active bacteria; e.g., hot or cold desert soils
Methodology
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
Structures of Model Compounds
Protoporphyrin IX of Heme
A Flavin: Riboflavin
A Diphosphopyridine Nucleotide: NAD
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
10 10
10
10
CE-ECD analysis of bacterial redox components
Control
Pseudomonas putida
Arthrobactor
10 M standards0.55
0.75
0.95
1.15
1.35
1.55
0 1 2 3 4 5 6 7 8
Time (min)
Response (
uA
)
10 uM SOL standard
Arthrobactor
Pseudomonas putida
Formic acid control
Conditions:25 um x 30 cm capillary25 mM borate/SDS20 kV separation potential4.7 uA average current4 s @ 5 kV EK injection
porphyrinsNAD FADQo riboflavin
niacinamide
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
Future Directions
•Square-wave or Cyclic voltammetric CE detection:
Redox potential & concentration information.
current
retention time
potential
O
O
O
O
Energy
•Series of reversible redox agents over the range of -1 to +1 volts may indicate life
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
Possible Lab on a Chip Design
The extraction module can be designed to handle either traditional solvents (e.g., DMF/ Borate / SDS or 1.0 M formic acid) or pressurized supercritical carbon dioxide.
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
Prototype CE-Square Wave Voltammetry System
Acknowledgement: Agilent Technologies
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Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas
Continuing Work
•Extraction / Analysis Methods: Additional Redox Molecules
• Rigorously Test Miniaturized CE /SW-Voltammetry System with Standards and Soil Extracts
• Additional Testing with Earth-based Soils (Craters of the Moon and others)
• Develop Collaborations: Miniaturized ES-MS/MS
• Completion of Primary Objective (4-6 Months: Finalize Conceptual Design of Life Detection System)