Download July 2000

Describing and Measuring Chemical Signatures of Life
Research Team
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
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
El
Form of energy: Chemical energy
The life forms we are seeking are living entities, not fossils.
Concepts and Approaches for Mars Exploration
July 18–20, 2000 Houston, Texas
•H2, NH3/NH4+, CH4, H2S
Electron Donors - Reducing Agents
•Metal ions (Fe2+), Metals
•Hydrocarbons
e-
Energy
Electron Acceptors - Oxidizing Agents
Concepts and Approaches for Mars Exploration
•O2, NO3-, SO2/SO3
•Metal Ions (Fe3+ and higher)
July 18–20, 2000 Houston, Texas
Respiratory Chain
(CH2O)n
eNAD+ + H+ + 2e-  NADH
eFMN + 2H+ + 2e-  FMNH2
eFAD + 2H+ + 2e-  FADH2
 - 0.70 volts
-0.32 volts
-0.30 V
-0.22 V
eCoQ + 2H+ + 2e-  CoQH2
0.04 V
e-
Cytochrome b (3+) e-  Cytochrome b (2+)
0.07 V
eCytochrome c1 (3+) e-  Cytochrome c1 (2+)
0.023 V
eCytochrome c (3+) e-  Cytochrome c (2+)
0.025 V
eCytochrome a (3+) e-  Cytochrome a (2+)
eCytochrome a3 (3+) e-  Cytochrome a3 (2+)
0.029 V
0.055 V
e-
O2 + 4H+ + 4e-  2H2O
Concepts and Approaches for Mars Exploration
+0.77 volts
July 18–20, 2000 Houston, Texas
Water
flow
waterfall
Concepts and Approaches for Mars Exploration
Vs.
series of dams
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
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
Concepts and Approaches for Mars Exploration
July 18–20, 2000 Houston, Texas
Sample Extraction
Module
•Sample will be obtained and life signature compounds
(redox agents) extracted by either a chemical solvent
or supercritical CO2
Compound
Separation Module
•Extracted compounds will be separated, probably by
capillary electrophoresis (CE).
Detection Module
Data Processing Module
Concepts and Approaches for Mars Exploration
•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.
July 18–20, 2000 Houston, Texas
Methodology
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
Concepts and Approaches for Mars Exploration
July 18–20, 2000 Houston, Texas
Structures of Model Compounds
A Flavin: Riboflavin
Protoporphyrin IX of Heme
Concepts and Approaches for Mars Exploration
A Diphosphopyridine Nucleotide: NAD
July 18–20, 2000 Houston, Texas
CE-ECD analysis of bacterial redox components
1.55
1.35
Response (uA)
Control
Conditions:
25 um x 30 cm capillary
25 mM borate/SDS
20 kV separation potential
4.7 uA average current
4 s @ 5 kV EK injection
Pseudomonas putida
1.15
10 uM SOL standard
Arthrobactor
Pseudomonas putida
Formic acid control
0.95
Arthrobactor
10
0.75
niacinamide
Qo riboflavin
NAD FAD
porphyrins
0.55
0
1
2
3
4
Time (min)
Concepts and Approaches for Mars Exploration
5
6
7
10
8
1010 M standards
10
July 18–20, 2000 Houston, Texas
Future Directions
•Square-wave or Cyclic voltammetric CE detection:
Redox potential & concentration information.
current
potential
Energy
O
O
O
O
•Series of reversible redox agents over the range
of -1 to +1 volts may indicate life
Concepts and Approaches for Mars Exploration
retention time
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.
Concepts and Approaches for Mars Exploration
July 18–20, 2000 Houston, Texas
Prototype CE-Square Wave Voltammetry System
Acknowledgement: Agilent Technologies
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)
Concepts and Approaches for Mars Exploration
July 18–20, 2000 Houston, Texas