Extraction and Separation of Chiral Amino Acids for Life Detection on Ocean Worlds Without Using Organic Solvents or Derivatization

Development and evaluation of a novel fluorescent chiral derivatization reagent DBD-S-M-Pro: first observation of four chiral amino acids in human hair

This study reports a novel fluorescent chiral derivatization reagent, 4-(N,N-dmethylaminosulfonyl)-2,1,3-benzoxadiazole-(2-succinimidoxy)-trans-2-methyl-L-proline (DBD-S-M-Pro), with a benzoxadiazole structure containing an N-hydroxysuccinimide activation group. DBD-S-M-Pro targets chiral amino-functional compounds under alkaline conditions without a condensation agent. Gradient elution was performed on a BEH C18 (100 × 2.1 mm, 1.7 μm) column with a mobile phase of 0.05% formic acid (FA) in 10 mM ammonium acetate (CH₃COONH₄) and 0.1% FA in acetonitrile or methanol. The efficiency of the chiral resolution was evaluated under excitation and emission wavelengths of 450 nm and 560 nm, respectively. The 19 chiral amino acids were separated in the range of 1.45-14.84. The resolutions of almost all DL-amino acids exceeded 1.5; the exceptions were serine (Ser) and lysine (Lys), with resolutions of 1.45 and 1.46, respectively. In addition, a new approach was devised for the simultaneous analysis of four chiral amino acids (DL-Glu, DL-Ala, DL-Val, and DL-Phe) in human hair. These amino acids were analyzed in the range of 12.5-400 pmol, with R² ≥ 0.9990, limits of detection (S/N = 3) of 4-10 pmol, and intraday and interday precisions of 0.57-6.23%. The average spikes in the hair recoveries were 89.76-111.54%, and the matrix effects were 92.47-102.40%. Next, the contents of free chiral amino acids in the hair samples of 10 healthy volunteers (five males and five females) were analyzed with this method, and the differences were compared. The developed DBD-S-M-Pro provides a novel strategy for the sensitive determination of free chiral amino acids in living organisms.

Microfluidic Chromatography for Enhanced Amino Acid Detection at Ocean Worlds

Increasing interest in the detection of biogenic signatures, such as amino acids, on icy moons and bodies within our solar system has led to the development of compact in situ instruments. Given the expected dilute biosignatures and high salinities of these extreme environments, purification of icy samples before analysis enables increased detection sensitivity. Herein, we outline a novel compact cation exchange method to desalinate proteinogenic amino acids in solution, independent of the type and concentration of salts in the sample. Using a modular microfluidic device, initial experiments explored operational limits of binding capacity with phenylalanine and three model cations, Na⁺, Mg²⁺, and Ca²⁺. Phenylalanine recovery (94-17%) with reduced conductivity (30-200 times) was seen at high salt-to-amino-acid ratios between 25:1 and 500:1. Later experiments tested competition between mixtures of 17 amino acids and other chemistries present in a terrestrial ocean sample. Recoveries ranged from 11% to 85% depending on side chain chemistry and cation competition, with concentration shown for select high affinity amino acids. This work outlines a nondestructive amino acid purification device capable of coupling to multiple downstream analytical techniques for improved characterization of icy samples at remote ocean worlds.

Analytical Chemistry Throughout This Solar System

One of the greatest and most long-lived scientific pursuits of humankind has been to discover and study the planetary objects comprising our solar system. Information gained from solar system observations, via both remote sensing and in situ measurements, is inherently constrained by the analytical (often chemical) techniques we employ in these endeavors. The past 50 years of planetary science missions have resulted in immense discoveries within and beyond our solar system, enabled by state-of-the-art analytical chemical instrument suites on board these missions. In this review, we highlight and discuss some of the most impactful analytical chemical instruments flown on planetary science missions within the last 20 years, including analytical techniques ranging from remote spectroscopy to in situ chemical separations. We first highlight mission-based remote and in situ spectroscopic techniques, followed by in situ separation and mass spectrometry analyses. The results of these investigations are discussed, and their implications examined, from worlds as close as Venus and familiar as Mars to as far away and exotic as Titan. Instruments currently in development for planetary science missions in the near future are also discussed, as are the promises their capabilities bring. Analytical chemistry is critical to understanding what lies beyond Earth in our solar system, and this review seeks to highlight how questions, analytical tools, and answers have intersected over the past 20 years and their implications for the near future.

Chirality in Organic and Mineral Systems: A Review of Reactivity and Alteration Processes Relevant to Prebiotic Chemistry and Life Detection Missions

Chirality is a central feature in the evolution of biological systems, but the reason for biology’s strong preference for specific chiralities of amino acids, sugars, and other molecules remains a controversial and unanswered question in origins of life research. Biological polymers tend toward homochiral systems, which favor the incorporation of a single enantiomer (molecules with a specific chiral configuration) over the other. There have been numerous investigations into the processes that preferentially enrich one enantiomer to understand the evolution of an early, racemic, prebiotic organic world. Chirality can also be a property of minerals; their interaction with chiral organics is important for assessing how post-depositional alteration processes could affect the stereochemical configuration of simple and complex organic molecules. In this paper, we review the properties of organic compounds and minerals as well as the physical, chemical, and geological processes that affect organic and mineral chirality during the preservation and detection of organic compounds. We provide perspectives and discussions on the reactions and analytical techniques that can be performed in the laboratory, and comment on the state of knowledge of flight-capable technologies in current and future planetary missions, with a focus on organics analysis and life detection.

Astrobiology of life on Earth

Astrobiology is mistakenly regarded by some as a field confined to studies of life beyond Earth. Here, we consider life on Earth through an astrobiological lens. Whereas classical studies of microbiology historically focused on various anthropocentric sub-fields (such as fermented foods or commensals and pathogens of crop plants, livestock and humans), addressing key biological questions via astrobiological approaches can further our understanding of all life on Earth. We highlight potential implications of this approach through the articles in this Environmental Microbiology special issue 'Ecophysiology of Extremophiles'. They report on the microbiology of places/processes including low-temperature environments and chemically diverse saline- and hypersaline habitats; aspects of sulphur metabolism in hypersaline lakes, dysoxic marine waters, and thermal acidic springs; biology of extremophile viruses; the survival of terrestrial extremophiles on the surface of Mars; biological soils crusts and rock-associated microbes of deserts; subsurface and deep biosphere, including a salticle formed within Triassic halite; and interactions of microbes with igneous and sedimentary rocks. These studies, some of which we highlight here, contribute to our understanding of the spatiotemporal reach of Earth'sfunctional biosphere, and the tenacity of terrestrial life. Their findings will help set the stage for future work focused on the constraints for life, and how organisms adapt and evolve to circumvent these constraints.