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

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

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

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

Concepts and Approaches for Mars Exploration July 18–20, 2000 Houston, Texas

waterfall Vs. series of dams

Water

flow

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

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

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.

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

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

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

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

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.

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)