Dataset Information

First observation of ²⁸O.

ABSTRACT: Subjecting a physical system to extreme conditions is one of the means often used to obtain a better understanding and deeper insight into its organization and structure. In the case of the atomic nucleus, one such approach is to investigate isotopes that have very different neutron-to-proton (N/Z) ratios than in stable nuclei. Light, neutron-rich isotopes exhibit the most asymmetric N/Z ratios and those lying beyond the limits of binding, which undergo spontaneous neutron emission and exist only as very short-lived resonances (about 10^-21 s), provide the most stringent tests of modern nuclear-structure theories. Here we report on the first observation of ²⁸O and ²⁷O through their decay into ²⁴O and four and three neutrons, respectively. The ²⁸O nucleus is of particular interest as, with the Z = 8 and N = 20 magic numbers^1,2, it is expected in the standard shell-model picture of nuclear structure to be one of a relatively small number of so-called 'doubly magic' nuclei. Both ²⁷O and ²⁸O were found to exist as narrow, low-lying resonances and their decay energies are compared here to the results of sophisticated theoretical modelling, including a large-scale shell-model calculation and a newly developed statistical approach. In both cases, the underlying nuclear interactions were derived from effective field theories of quantum chromodynamics. Finally, it is shown that the cross-section for the production of ²⁸O from a ²⁹F beam is consistent with it not exhibiting a closed N = 20 shell structure.

SUBMITTER: Kondo Y

PROVIDER: S-EPMC10630140 | biostudies-literature | 2023 Aug

REPOSITORIES: biostudies-literature

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First observation of <sup>28</sup>O.

Kondo Y Y Achouri N L NL Falou H Al HA Atar L L Aumann T T Baba H H Boretzky K K Caesar C C Calvet D D Chae H H Chiga N N Corsi A A Delaunay F F Delbart A A Deshayes Q Q Dombrádi Zs Z Douma C A CA Ekström A A Elekes Z Z Forssén C C Gašparić I I Gheller J-M JM Gibelin J J Gillibert A A Hagen G G Harakeh M N MN Hirayama A A Hoffman C R CR Holl M M Horvat A A Horváth Á Á Hwang J W JW Isobe T T Jiang W G WG Kahlbow J J Kalantar-Nayestanaki N N Kawase S S Kim S S Kisamori K K Kobayashi T T Körper D D Koyama S S Kuti I I Lapoux V V Lindberg S S Marqués F M FM Masuoka S S Mayer J J Miki K K Murakami T T Najafi M M Nakamura T T Nakano K K Nakatsuka N N Nilsson T T Obertelli A A Ogata K K de Oliveira Santos F F Orr N A NA Otsu H H Otsuka T T Ozaki T T Panin V V Papenbrock T T Paschalis S S Revel A A Rossi D D Saito A T AT Saito T Y TY Sasano M M Sato H H Satou Y Y Scheit H H Schindler F F Schrock P P Shikata M M Shimizu N N Shimizu Y Y Simon H H Sohler D D Sorlin O O Stuhl L L Sun Z H ZH Takeuchi S S Tanaka M M Thoennessen M M Törnqvist H H Togano Y Y Tomai T T Tscheuschner J J Tsubota J J Tsunoda N N Uesaka T T Utsuno Y Y Vernon I I Wang H H Yang Z Z Yasuda M M Yoneda K K Yoshida S S

Nature 20230830 7976

Subjecting a physical system to extreme conditions is one of the means often used to obtain a better understanding and deeper insight into its organization and structure. In the case of the atomic nucleus, one such approach is to investigate isotopes that have very different neutron-to-proton (N/Z) ratios than in stable nuclei. Light, neutron-rich isotopes exhibit the most asymmetric N/Z ratios and those lying beyond the limits of binding, which undergo spontaneous neutron emission and exist onl ...[more]

PMID: 37648757

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Project description:FliA (also known as σ28), a member of the bacterial σ70 family of transcription factors, directs RNA polymerase to flagellar late (class 3) promoters and initiates transcription. FliA has been studied in several bacteria, yet its role in spirochetes has not been established. In this report, we identify and functionally characterize a FliA homolog (TDE2683) in the oral spirochete Treponema denticola. Computational, genetic, and biochemical analyses demonstrated that TDE2683 has a structure similar to that of the σ28 of Escherichia coli, binds to σ28-dependent promoters, and can functionally replace the σ28 of E. coli. However, unlike its counterparts from other bacteria, TDE2683 cannot be deleted, suggesting its essential role in the survival of T. denticola. In vitro site-directed mutagenesis revealed that E221 and V231, two conserved residues in the σ4 region of σ28, are indispensable for the binding activity of TDE2683 to the σ28-dependent promoter. We then mutated these two residues in T. denticola and found that the mutations impair the expression of flagellin and chemotaxis genes and bacterial motility as well. Cryo-electron tomography analysis further revealed that the mutations disrupt the flagellar symmetry (i.e., number and placement) of T. denticola. Collectively, these results indicate that TDE2683 is a σ28 transcription factor that regulates the class 3 gene expression and controls the flagellar symmetry of T. denticola. To the best of our knowledge, this is the first report establishing the functionality of FliA in spirochetes. IMPORTANCE Spirochetes are a group of medically important but understudied bacteria. One of the unique aspects of spirochetes is that they have periplasmic flagella (PF, also known as endoflagella) which give rise to their unique spiral shape and distinct swimming behaviors and play a critical role in the pathophysiology of spirochetes. PF are structurally similar to external flagella, but the underpinning mechanism that regulates PF biosynthesis and assembly remains largely unknown. By using the oral spirochete Treponema denticola as a model, this report provides several lines of evidence that FliA, a σ28 transcriptional factor, regulates the late flagellin gene (class 3) expression, PF assembly, and flagellar symmetry as well, which provides insights into flagellar regulation and opens an avenue to investigate the role of σ28 in spirochetes.

Project description:BackgroundUnbalanced inflammatory response is a critical feature of sepsis, a life-threatening condition with significant global health burdens. Immune dysfunction, particularly that involving different immune cells in peripheral blood, plays a crucial pathophysiological role and shows early warning signs in sepsis. The objective is to explore the relationship between sepsis and immune subpopulations in peripheral blood, and to identify patients with a higher risk of 28-day mortality based on immunological subtypes with machine-learning (ML) model.MethodsPatients were enrolled according to the sepsis-3 criteria in this retrospective observational study, along with age- and sex-matched healthy controls (HCs). Data on clinical characteristics, laboratory tests, and lymphocyte immunophenotyping were collected. XGBoost and k-means clustering as ML approaches, were employed to analyze the immune profiles and stratify septic patients based on their immunological subtypes. Cox regression survival analysis was used to identify potential biomarkers and to assess their association with 28-day mortality. The accuracy of biomarkers for mortality was determined by the area under the receiver operating characteristic (ROC) curve (AUC) analysis.ResultsThe study enrolled 100 septic patients and 89 HCs, revealing distinct lymphocyte profiles between the two groups. The XGBoost model discriminated sepsis from HCs with an area under the receiver operating characteristic curve of 1.0 and 0.99 in the training and testing set, respectively. Within the model, the top three highest important contributions were the percentage of CD38+CD8+T cells, PD-1+NK cells, HLA-DR+CD8+T cells. Two clusters of peripheral immunophenotyping of septic patients by k-means clustering were conducted. Cluster 1 featured higher proportions of PD1+ NK cells, while cluster 2 featured higher proportions of naïve CD4+T cells. Furthermore, the level of PD-1+NK cells was significantly higher in the non-survivors than the survivors (15.1% vs 8.6%, P<0.01). Moreover, the levels of PD1+ NK cells combined with SOFA score showed good performance in predicting the 28-day mortality in sepsis (AUC=0.91,95%CI 0.82-0.99), which is superior to PD1+ NK cells only(AUC=0.69, sensitivity 0.74, specificity 0.64, cut-off value of 11.25%). In the multivariate Cox regression, high expression of PD1+ NK cells proportion was related to 28-day mortality (aHR=1.34, 95%CI 1.19 to 1.50; P<0.001).ConclusionThe study provides novel insights into the association between PD1+NK cell profiles and prognosis of sepsis. Peripheral immunophenotyping could potentially stratify the septic patients and identify those with a high risk of 28-day mortality.

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First observation of ²⁸O.

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First observation of <sup>28</sup>O.

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First observation of 28O.

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First observation of &lt;sup&gt;28&lt;/sup&gt;O.

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First observation of ²⁸O.

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