321: All five canonical nucleobases detected in Ryugu samples

Koga T et al., Nature Astronomy - Ryugu asteroid samples analyzed by HPLC/ESI-HRMS reveal all five canonical nucleobases (adenine, guanine, cytosine, thymine, uracil) and distribution linked to ammonia. Key terms: Ryugu, nucleobases, adenine, HPLC/ESI-HRMS, purine-to-pyrimidine ratio.

Study Highlights:
The team analysed Ryugu aggregate samples A0480 and C0370 and the Orgueil meteorite using water and HCl extraction followed by HPLC/ESI-HRMS, CE-HRMS and nano-EA/IRMS. They identified all five canonical nucleobases and measured total nucleobase concentrations (C0370 = 1,577 pmol g−1) and purine-to-pyrimidine (Pu/Py) ratios of ~1.1–1.2 in Ryugu contrasted with 0.099 in Orgueil and 3.4 in Murchison. A strong negative correlation (R2=0.89) between Pu/Py ratios and ammonia across Ryugu, Bennu and Orgueil implies ammonia availability influenced nucleobase formation pathways. The results support widespread abiotic nucleobase synthesis in carbonaceous parent bodies and potential delivery of diverse prebiotic molecules to early Earth.

Conclusion:
All five canonical nucleobases are present in Ryugu samples and their purine-to-pyrimidine distributions, which correlate with ammonia, indicate shared but environment-dependent formation pathways on carbonaceous parent bodies.

Music:
Enjoy the music based on this article at the end of the episode.

Article title:
A complete set of canonical nucleobases in the carbonaceous asteroid (162173) Ryugu

First author:
Koga T

Journal:
Nature Astronomy

DOI:
10.1038/s41550-026-02791-z

Reference:
Koga T., Ogawa N. O., Ohkouchi N., Oba Y., Takano Y., Naraoka H., Sasaki K., Sato H., Yoshimura T. et al. A complete set of canonical nucleobases in the carbonaceous asteroid (162173) Ryugu. Nature Astronomy (2026). https://doi.org/10.1038/s41550-026-02791-z

License:
This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) - https://creativecommons.org/licenses/by/4.0/

Support:
Base by Base – Stripe donations: https://donate.stripe.com/7sY4gz71B2sN3RWac5gEg00

Official website https://basebybase.com

On PaperCast Base by Base you’ll discover the latest in genomics, functional genomics, structural genomics, and proteomics.

Episode link: https://basebybase.com/episodes/ryugu-nucleobases-ammonia-correlation

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-03-20.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited transcript sections presenting nucleobase detection, extraction/analytical workflow, concentration data for Ryugu samples, Pu/Py ratios across samples, ammonia correlation, abiotic/isomer evidence (6-methyluracil, hypoxanthine isomer), Chargaff's rule discussion, isotopic signatures, contamination controls, and
- transcript topics: Detection of all five canonical nucleobases in Ryugu; Sequential extraction workflow (water then HCl) and analytical methods (HPLC/ESI-HRMS, CE-HRMS, nano-EA/IRMS); Concentrations of nucleobases in Ryugu samples A0480 and C0370; comparison to Orgueil; Pu/Py (purine/pyrimidine) ratios across Ryugu, Bennu, Orgueil, and Murchison; Correlation between Pu/Py ratios and ammonia concentrations; Evidence for abiotic nucleobase formation: non-biological isomers (6-methyluracil) and hypoxanthine isomer

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 6
- claims flagged for review: 0
- metadata checks passed: 4
- metadata issues found: 0

Metadata Audited:
- article_doi
- article_title
- article_journal
- license

Factual Items Audited:
- All...

Chapters

(00:00:00) - Decoding the cosmic delivery of life
(00:03:18) - The Ryugu Meteorite
(00:08:52) - The Prebiotic grocery list of Earth
(00:14:13) - The structure of DNA in the asteroid
(00:15:38) - The Search for Life on Earth
(00:21:26) - What Does This All Mean for Life?
(00:26:39) - Falling Into You

Det här avsnittet är hämtat från ett öppet RSS-flöde och publiceras inte av Podme. Det kan innehålla reklam.

Avsnitt(445)

444: Many-eyes or Sentinels? How Cost Curvature Shapes Collective Vigilance

Pilgrim C et al., PNAS - A minimal analytical model shows that whether animal groups adopt distributed low-level vigilance (many-eyes) or concentrated high-vigilance roles (sentinels) depends on how i...

19 Aug 24min

443: 5D‑ASO boosts exon 51 skipping and restores dystrophin in DMD models

Feng P et al., PNAS - This paper describes a bipartite antisense oligonucleotide (5D‑ASO) design that appends a short 5′ splice site decoy tail to improve exon skipping, demonstrating robust efficacy ...

18 Aug 19min

442: When pumps go missing: Ca2+ control of PMCA2 in Tmc1 deafness mutants

Rolseth AB et al., Proceedings of the National Academy of Sciences (PNAS) - This study links reduced Ca2+ entry through mutant TMC1 mechanotransducer channels to decreased PMCA2 pump density in outer ...

17 Aug 22min

441: Evolutionary mapping of Cav1.3 functional sites

Tang X et al., PNAS - The authors apply an evolutionary sequence-covariation model to the Cav1.3 (CACNA1D) α1-subunit, map predicted pathogenicity onto structural models, and validate five predicted s...

14 Aug 24min

440: DENV-4: Suppressing DNA Repair and Causing Genome Damage

Lamkina EN et al., PNAS - This episode reviews a PNAS brief report showing that DENV-4 infection induces marked DNA damage in infected cells while broadly suppressing transcription of DNA repair pathw...

12 Aug 23min

439: Coembedding Sequence and Structure: CLSS Maps the Protein Universe

Longo LM et al., PNAS - This episode summarizes a PNAS study introducing CLSS, a contrastive two-tower protein language model that coembeds domain sequences, structures, and subsequences into a shared...

11 Aug 23min

438: Mapping AIRE: a proactive atlas of 9,790 missense variants

Axakova A et al., The American Journal of Human Genetics - Axakova et al. generated a variant effect map for AIRE using an insulin‑promoter GFP reporter in HEK293 cells to measure the functional impac...

10 Aug 24min

437: Cell villages and Dirichlet modeling map human cell fitness genetics

Hanson C et al., The American Journal of Human Genetics - Hanson et al. combine pooled multi-donor human neural progenitor cell "villages" with Townlet, a hierarchical Dirichlet regression model, to e...

9 Aug 28min