[Paper Review] Meteoritic Proteins with Glycine, Iron and Lithium

Malcolm W. McGeoch, Sergei Dikler+1 more|arXiv (Cornell University)|Feb 21, 2021

Astro and Planetary Science26 references4 citations

TL;DR

The study identifies novel extraterrestrial polymer amides—hemolithin (2320 Da) and hemoglycin (1494 Da)—in CV3 carbonaceous chondrites (Acfer 086, Allende, KABA), composed of glycine, hydroxy-glycine, iron, oxygen, and lithium. Using MALDI mass spectrometry and 3D imaging of Folch-extracted particles, the authors demonstrate covalent triskelion structures linked by silicon, with isotopic enrichment (2H > 25,700 ppm) confirming extraterrestrial origin and extended lattice formation via m/z 4641+ fragments.

ABSTRACT

We report that polymer amide [1] with a protein backbone of mainly glycine units and iron is present in the CV3 meteorites Acfer 086, Allende and KABA. The evidence for this is from particles of these meteorites after Folch extraction being analyzed by MALDI mass spectrometry and from the 3D physical structures that form in the various Folch solvent phases. The two physical forms we observe are branching rods and entrapping spheres on the 100micron scale. Two potential molecular structures of polymer amide are presented in this report. One we term hemolithin of mass 2320Da, contains glycine, hydroxy-glycine, Fe, O and Li. The other, we term hemoglycin of mass 1494Da is of glycine, hydroxy-glycine, Fe and O. Hemoglycin is connected covalently in triplets by silicon to form a triskelion. Analysis of the complete spectrum of isotopes associated with each molecular fragment shows very high 2H enhancement above terrestrial averaging 25,700 parts per thousand (sigma = 3,500, n=15), confirming extra-terrestrial origin and hence the existence of these molecules within the asteroid parent body of the CV3 meteorite class. The hemoglycin triskelia join via silicon bonds into an extended lattice, as seen in mass spectrometry of lattice fragments at m/z 4641 and above [2]. The identification of hemolithin and hemoglycin required careful methodology at room temperature with the minimum of steps up to mass spectrometry analysis ensuring that only the laser step fragmented the molecules. The 3D structures were imaged through permanently closed Folch extraction V-vials at a magnification of 10.

Motivation & Objective

• To identify and characterize novel organic polymers in carbonaceous chondrites with potential biological relevance.
• To determine the structural and isotopic evidence for extraterrestrial origin of complex organic molecules in meteorites.
• To investigate the 3D physical morphology and molecular architecture of these polymers in Folch solvent phases.
• To establish a low-temperature, minimal-step analytical protocol preserving molecular integrity during mass spectrometry.
• To explore the role of silicon in linking trimeric hemoglycin units into extended lattices.

Proposed method

• Conducted Folch extraction of meteorite particles at room temperature to isolate organic phases with minimal thermal or chemical disruption.
• Employed MALDI mass spectrometry to detect intact molecular ions and fragment patterns of polymer amides.
• Imaged 3D physical structures (branching rods and entrapping spheres) in sealed V-vials at 10x magnification.
• Analyzed isotopic distributions, particularly 2H enrichment (25,700 ppm), to confirm extraterrestrial origin.
• Proposed molecular structures: hemolithin (2320 Da) and hemoglycin (1494 Da), both with Fe, O, and glycine derivatives.
• Identified covalent triskelion formation of hemoglycin via silicon bonds, with lattice fragments detected at m/z ≥ 4641.

Experimental results

Research questions

• RQ1 Do complex, protein-like polymer amides exist in CV3 carbonaceous chondrites?
• RQ2 Can isotopic anomalies such as extreme 2H enrichment confirm extraterrestrial origin of these organic molecules?
• RQ3 What are the 3D physical morphologies of these molecules in Folch solvent phases?
• RQ4 How are the hemoglycin units structurally linked to form extended lattices?
• RQ5 Can a low-temperature, minimal-step analytical method preserve and detect fragile organic polymers in meteorites?

Key findings

• Hemolithin (2320 Da) and hemoglycin (1494 Da) were identified in CV3 meteorites Acfer 086, Allende, and KABA.
• Hemoglycin forms covalent triskelion structures linked by silicon, with lattice fragments observed at m/z 4641 and above.
• Isotopic analysis revealed 2H enrichment of 25,700 parts per thousand, significantly above terrestrial levels (σ = 3,500, n=15), confirming extraterrestrial origin.
• Three-dimensional structures—branching rods and entrapping spheres—were imaged at 100 µm scale in sealed Folch extraction vials.
• The molecules were preserved using a room-temperature, minimal-step protocol, with laser desorption as the sole fragmentation step in MALDI-MS.
• The presence of glycine, iron, lithium, and oxygen in these polymers suggests a novel class of meteoritic organic materials with potential prebiotic relevance.