Mohiuddin Kabir

Two of the fundamental questions expressed in the Astrobiology Roadmap are “How does life begin and evolve?” and “Does life exist elsewhere in the universe?” Understanding the distribution of complex organic molecules associated with living things is essential to answering both of these questions. Microbiologist Mohiuddin Kabir is working with his NASA partner to develop a new technology for measuring the abundance of an array of organic molecules in complex mixtures with stereochemical specificity without chemical modification. Various instruments are under development to search for organic amines, amino acids and polycyclic aromatic hydrocarbons in extraterrestrial environments. The most mature of these is based on gas chromatography mass spectrometry (GCMS). This technology is at the heart of an instrument suite called SAM (Sample Analysis at Mars) that is part of the Mars Science Laboratory mission.

In GCMS instrumentation samples must be volatilized, either by pyrolysis or by chemical deriviatization. Pyrolysis breaks down complex molecules into smaller units that are analyzable but stereochemistry cannot be resolved. Derivatization reacts analytes with chemicals that increase their volatility, enabling GCMS analysis. Under appropriate conditions, stereochemistry of derivatized molecules can be resolved by GCMS. GCMS separations are, however, sometimes subject to degeneracy when multiple compounds have the same mobility and mass. This is particularly troublesome when the sample is not well characterized as would be the case in extraterrestrial environments. Uncharacterized chemical reactivity in the sample may also interfere with derivatization chemistry. The UREY instrument, planned for inclusion in the ESA ExoMars mission, contains the Mars Organic Analyzer (MOA) for the purpose of analyzing amines and amino acids on Mars. This instrument is based on micro capillary electrophoresis (µCE) combined with preparation of the sample by water extraction and chemical derivatization. The derivatization in this case adds a fluorescent dye to the analyte to facilitate detection. This instrument is extremely sensitive but has limitations similar to GCMS in that there is some risk that unknown compounds in the sample will either obscure the capillary electrophoresis results or interfere with the derivatization chemistry. Furthermore, the current derivatization chemistry only reacts with amines, leaving the instrument unable to detect sugars and other polyols that lack an amine. To overcome the problems associated with existing technologies, Mohiuddin Kabir and his NASA partner are developing protein based biosensors in order to detect organic amines, amino acids and polycyclic aromatic hydrocarbons in extraterrestrial environments that does not require the samples to be modified.