9:00 AM - 9:15 AM
[PPS07-01] All five nucleobases detected in samples from the asteroid Ryugu
★Invited Papers
Keywords:Nucleobase, Ryugu, Carbonaceous asteroid, HPLC/HRMS
Introduction: Extraterrestrial nucleobases have garnered significant interest due to their role in the chemical evolution of primordial molecules within the Solar System and their potential contribution to the emergence of genetic functions on early Earth. High-performance liquid chromatography coupled with electrospray ionization high-resolution mass spectrometry (HPLC/ESI-HRMS) was employed to determine the concentration of uracil, a pyrimidine nucleobase, in hot water extracts of C-type asteroid Ryugu samples, yielding values between 11 and 32 ppb (ng/g-sample) [1]. Although purine nucleobases were not identified in these initial analyses of Ryugu's soluble organic matter, subsequent methodological advancements in extraction, purification, and analysis revealed that the Murchison meteorite contained more than ten times the nucleobases previously detected in HCl extracts [2]. The application of these advanced techniques led to the detection of all five canonical nucleobases—uracil, cytosine, thymine, adenine, and guanine—in the B-type asteroid Bennu sample [3].
Building on these refined techniques, we conducted further analyses of Ryugu samples to reassess nucleobase distributions in this C-type asteroid. To this end, we applied a two-step extraction procedure and performed targeted analyses using HPLC/ESI-HRMS, enabling a direct comparison with nucleobase distributions observed in the Bennu sample.
Methods and Results: The Ryugu aggregate samples, A0480 (11.9 mg) and C0370 (8.3 mg), were obtained through JAXA’s 3rd Announcement of Opportunity (AO3). We applied a two-step extraction procedure: (1) water extraction at 25 ºC via sonication (H2O extracts) and (2) 6 M HCl extraction at 110 ºC for 20 hours (HCl extracts), followed by purification through cation exchange column chromatography. Targeted analyses via HPLC/ESI-HRMS confirmed the presence of all five nucleobases—uracil, cytosine, thymine, adenine, and guanine. Among them, guanine, a purine nucleobase, exhibited the highest concentration, with concentrations of 67 ppb in the HCl extract and 17 ppb in the H2O extract of the C0370 sample, conclusively identified through MS/MS experiments.
The total nucleobase abundance in the C0370 sample was approximately one-third of that found in the HCl extract of Bennu [3]. Notably, the purine-to-pyrimidine ratio differed significantly between Ryugu (2.0–2.3) and Bennu (0.5), implying distinct organic chemical pathways for nucleobase synthesis in extraterrestrial environments. The detection of all five nucleobases in carbonaceous asteroids (i.e., Ryugu and Bennu) underscores their cosmochemical and prebiotic significance, highlighting the widespread distribution of genetic material components during the Solar System's formation and their potential role as molecular precursors of DNA and RNA.
Building on these refined techniques, we conducted further analyses of Ryugu samples to reassess nucleobase distributions in this C-type asteroid. To this end, we applied a two-step extraction procedure and performed targeted analyses using HPLC/ESI-HRMS, enabling a direct comparison with nucleobase distributions observed in the Bennu sample.
Methods and Results: The Ryugu aggregate samples, A0480 (11.9 mg) and C0370 (8.3 mg), were obtained through JAXA’s 3rd Announcement of Opportunity (AO3). We applied a two-step extraction procedure: (1) water extraction at 25 ºC via sonication (H2O extracts) and (2) 6 M HCl extraction at 110 ºC for 20 hours (HCl extracts), followed by purification through cation exchange column chromatography. Targeted analyses via HPLC/ESI-HRMS confirmed the presence of all five nucleobases—uracil, cytosine, thymine, adenine, and guanine. Among them, guanine, a purine nucleobase, exhibited the highest concentration, with concentrations of 67 ppb in the HCl extract and 17 ppb in the H2O extract of the C0370 sample, conclusively identified through MS/MS experiments.
The total nucleobase abundance in the C0370 sample was approximately one-third of that found in the HCl extract of Bennu [3]. Notably, the purine-to-pyrimidine ratio differed significantly between Ryugu (2.0–2.3) and Bennu (0.5), implying distinct organic chemical pathways for nucleobase synthesis in extraterrestrial environments. The detection of all five nucleobases in carbonaceous asteroids (i.e., Ryugu and Bennu) underscores their cosmochemical and prebiotic significance, highlighting the widespread distribution of genetic material components during the Solar System's formation and their potential role as molecular precursors of DNA and RNA.