ASTID

Stereospecific sensors for amino acids and carbohydrates in extraterrestrial environments

PI: Chad Paavola

The search for organic molecule biomarkers is an important element of the search for extraterrestrial life and the study of prebiotic environments. In research funded by a previous ASTID grant, our team developed sensors for amino acids and sugars based on proteins. This project aims to radically improve the signal to noise ratio (S/N) of the technology and to focus the amino acid specificities on those most relevant for astrobiology. It will also test the sensing elements in a planar optical waveguide flow cell. Our team has developed protein-based sensing elements with S/N of 5-10 and the present goal is > 50. One approach will maximize signal change, the other will utilize the full range of signal change. Sensing elements the team has developed use resonance energy transfer to generate signal change that depends on the protein’s analyte-dependent change in shape. Substitution of long-lifetime luminescent compounds for organic fluorophore resonant energy donors will improve the signal over background by 50-100 fold. Placing the resonant energy transfer donor on a separate peptide selected to bind only the protein-analyte complex results in larger distance change between donor and acceptor than conformational change, resulting in maximum signal with analyte and minimum signal without. Amino acid sensing will focus on those present in extraterrestrial environments, based on studies of meteorites. The chiral amino acids alanine, valine, isovaline and alpha-aminoisobutyric acid are abundant in carbonaceous chondrites and represent compounds common in terrestrial life (alanine, valine) or uncommon (isovaline, alpha-aminoisobutyric acid). Specificities for these amino acids will be combined with specificity for D/L-amino acids and added to glucose and ribose sensors being developed in previously funded research, to produce ten sensing elements for amino acids and sugars that can be deployed with existing sampling hardware as a stand-alone
instrument or together with other instrumentation using planar waveguide or standard optics.