Hemolithin: a Meteoritic Protein containing Iron and Lithium (2002.11688v1)

Abstract: This paper characterizes the first protein to be discovered in a meteorite. Amino acid polymers previously observed in Acfer 086 and Allende meteorites [1,2] have been further characterized in Acfer 086 via high precision MALDI mass spectrometry to reveal a principal unified structure of molecular weight 2320 Daltons that involves chains of glycine and hydroxy-glycine residues terminated by iron atoms, with additional oxygen and lithium atoms. Signal-to-noise ratios up to 135 have allowed the quantification of iron and lithium in the various MALDI fragments via the isotope satellites due to their respective minority isotopic masses 54Fe and 6Li. Analysis of the complete spectrum of isotopes associated with each molecular fragment shows 2H enhancements above terrestrial averaging 25,700 parts per thousand (sigma = 3,500, n=15), confirming extra-terrestrial origin and hence the existence of this molecule within the asteroid parent body of the CV3 meteorite class. The molecule is tipped by an iron-oxygen-iron grouping that in other terrestrial contexts has been proposed to be capable of absorbing photons and splitting water into hydroxyl and hydrogen moieties.

• The paper details the first detection of an extraterrestrial metalloprotein, hemolithin, with a molecular weight of 2320 Da using MALDI mass spectrometry.
• The paper employs MALDI-TOF/TOF spectrometry with varied matrices to accurately resolve isotopic signatures and identify iron and lithium atoms.
• The paper shows significant isotopic enrichment of deuterium and nitrogen-15, underscoring a non-terrestrial origin and potential photocatalytic applications.

Insights on Hemolithin: A Meteoritic Protein Containing Iron and Lithium

The paper in question delineates the identification and characterization of the first known protein from an extraterrestrial source, found within the Acfer 086 meteorite. This protein, named hemolithin, potentially underscores significant insights into the abiotic synthesis of biopolymers in pre-solar systems or ancient molecular clouds.

Summary of Findings

Through high-precision Matrix-Assisted Laser Desorption/Ionization (MALDI) mass spectrometry, the paper detects amino acid polymers in the Acfer 086 meteorite, specifically comprising glycine and hydroxy-glycine residues. The central structure elucidated has a molecular weight of 2320 Da and is electrically terminated with iron and lithium atoms. The mass spectroscopic analysis indicated a notable excess of deuterium (D) and nitrogen-15, marking its extraterrestrial origins. The isotopic reading shows a significant enhancement, approximately 25,700 parts per thousand above terrestrial values, suggesting a proto-solar or interstellar environment of genesis.

Detailed Analytical Approach

The methodology embraced MALDI-TOF and MALDI-TOF/TOF spectrometry to resolve the metalloprotein structure at the molecular level. Different MALDI matrices (alpha-cyano-4-hydroxycinnamic acid, sinapinic acid, and dihydroxybenzoic acid) were employed in tandem to differentiate relevant signals from matrix artefacts. The paper focused on isotope ratios, particularly isotopic satellites derived from Fe and Li, to ensure the validity of metalloproein composition against terrestrial standards.

Significantly, the isotopic analysis disentangles the molecular spectra to support the presence of multiple iron and lithium atoms. The deconvolution of satellite peaks confirmed non-terrestrial isotopic abundances, validating the presence of iron-oxygen groups capable of photon absorption and hypothesized to be involved in photocatalytic water splitting.

Implications and Future Developments

The paper offers profound implications on our understanding of chemical evolution and the potential pathways for prebiotic chemistry beyond terrestrial realms. The discovery of hemolithin suggests that proteins or protein-like structures could be synthesized in space, challenging terrestrial-centric notions of biochemical evolution. The configuration involving FeO F3 motifs merits further exploration into their photocatalytic properties, which could not only change perspectives on cometary or asteroidal chemistry but also expand interest in metalloproteins in exoplanetary environments.

A continued focus on characterizing such extraterrestrial biopolymers may shed light on the molecular diversity prevalent in space, potentially bridging gaps in our understanding of the origins of life. Future developments could explore the extent to which plasmidized amino acid structures participate in or mediate photochemical reactions under cosmic conditions. This work also lays a framework for modeling similar biostructures incubated under different astrophysical environments through computational approaches such as MMFF molecular field modeling.

Conclusion

The characterization of hemolithin within the Acfer 086 meteorite represents a pivotal stride in astrobiology and molecular physics. While providing evidence of complex organic chemistry beyond Earth, the isotopic excesses and structural nuances unveiled invite a reevaluation of early molecular formation conditions across interstellar spaces. Continued analytical advancements and interstellar sample retrieval missions promise to augment our understanding of universal biological precursors, as suggested by this fascinating research.