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Project Progress

A New Molecular Recognition Instrument for Astrobiological Applications (dm)

Protein chip-based molecular recognition technology is being developed as a method for detecting life on Earth and other solar system bodies. The Ciphergen Biosystems ProteinChip Reader (PBSII) is dependent on the surface chemistry of small chips to selectively capture femtomole amounts of complex mixtures of organic molecules for molecular weight determination by time of flight mass spectrometry. By using different chips, experiments can be designed to recognize a complex combination of molecular markers by selecting a series of chip surface chemistries to pull apart complex mixtures.

Proteomics: We determined the protein profile of Shewanella putrefascens, a microorganism that is commonly isolated from geochemical gradient zones in which dissolved oxygen levels range from fully oxic to completely anoxic. Replicate analyses of the chip detected 62 peptides or proteins from 754 to 237,954 daltons, some of which corresponded to molecular weights of protein identified from the genome. The instrument detected proteins in the lower picomole to higher femtomole range.

Geochemical Studies: On Earth, as well as Europa, the bulk of organic carbon molecules in the world’s oceans are found dissolved in seawater. However, the chemical composition of dissolved organic matter is complex and poorly understood, making it a good proxy to what might exist on Europa or Mars. The distribution of organic molecules was determined to see whether large proteins or microbial cell wall fragments could be detected from the Pacific Ocean (100 m depth) and from a riverine-derived filtrate (< 0.2 micrometers). The molecular weight distribution precludes any intact proteins in the sample. The molecules between 1000 and 6,000 daltons could be explained by units of microbial cell walls. Last and most important, the SELDI technique identified a biosignature in both of the samplesâ??the common 14 peaks and an additional biological source in oceanic DOM, not found in the riverine sample.