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71.
Cederwall B Moradi FG Bäck T Johnson A Blomqvist J Clément E de France G Wadsworth R Andgren K Lagergren K Dijon A Jaworski G Liotta R Qi C Nyakó BM Nyberg J Palacz M Al-Azri H Algora A de Angelis G Ataç A Bhattacharyya S Brock T Brown JR Davies P Di Nitto A Dombrádi Z Gadea A Gál J Hadinia B Johnston-Theasby F Joshi P Juhász K Julin R Jungclaus A Kalinka G Kara SO Khaplanov A Kownacki J La Rana G Lenzi SM Molnár J Moro R Napoli DR Singh BS Persson A Recchia F Sandzelius M Scheurer JN Sletten G 《Nature》2011,469(7328):68-71
Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing, in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus (92)Pd. Gamma rays emitted following the (58)Ni((36)Ar,2n)(92)Pd fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution γ-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis. 相似文献
72.
Lord C Bhandari D Menon S Ghassemian M Nycz D Hay J Ghosh P Ferro-Novick S 《Nature》2011,473(7346):181-186
How the directionality of vesicle traffic is achieved remains an important unanswered question in cell biology. The Sec23p/Sec24p coat complex sorts the fusion machinery (SNAREs) into vesicles as they bud from the endoplasmic reticulum (ER). Vesicle tethering to the Golgi begins when the tethering factor TRAPPI binds to Sec23p. Where the coat is released and how this event relates to membrane fusion is unknown. Here we use a yeast transport assay to demonstrate that an ER-derived vesicle retains its coat until it reaches the Golgi. A Golgi-associated kinase, Hrr25p (CK1δ orthologue), then phosphorylates the Sec23p/Sec24p complex. Coat phosphorylation and dephosphorylation are needed for vesicle fusion and budding, respectively. Additionally, we show that Sec23p interacts in a sequential manner with different binding partners, including TRAPPI and Hrr25p, to ensure the directionality of ER-Golgi traffic and prevent the back-fusion of a COPII vesicle with the ER. These events are conserved in mammalian cells. 相似文献
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Ospelkaus C Warring U Colombe Y Brown KR Amini JM Leibfried D Wineland DJ 《Nature》2011,476(7359):181-184
Control over physical systems at the quantum level is important in fields as diverse as metrology, information processing, simulation and chemistry. For trapped atomic ions, the quantized motional and internal degrees of freedom can be coherently manipulated with laser light. Similar control is difficult to achieve with radio-frequency or microwave radiation: the essential coupling between internal degrees of freedom and motion requires significant field changes over the extent of the atoms' motion, but such changes are negligible at these frequencies for freely propagating fields. An exception is in the near field of microwave currents in structures smaller than the free-space wavelength, where stronger gradients can be generated. Here we first manipulate coherently (on timescales of 20 nanoseconds) the internal quantum states of ions held in a microfabricated trap. The controlling magnetic fields are generated by microwave currents in electrodes that are integrated into the trap structure. We also generate entanglement between the internal degrees of freedom of two atoms with a gate operation suitable for general quantum computation; the entangled state has a fidelity of 0.76(3), where the uncertainty denotes standard error of the mean. Our approach, which involves integrating the quantum control mechanism into the trapping device in a scalable manner, could be applied to quantum information processing, simulation and spectroscopy. 相似文献
77.
Oxysterols direct immune cell migration via EBI2 总被引:1,自引:0,他引:1
Hannedouche S Zhang J Yi T Shen W Nguyen D Pereira JP Guerini D Baumgarten BU Roggo S Wen B Knochenmuss R Noël S Gessier F Kelly LM Vanek M Laurent S Preuss I Miault C Christen I Karuna R Li W Koo DI Suply T Schmedt C Peters EC Falchetto R Katopodis A Spanka C Roy MO Detheux M Chen YA Schultz PG Cho CY Seuwen K Cyster JG Sailer AW 《Nature》2011,475(7357):524-527
Epstein-Barr virus-induced gene 2 (EBI2, also known as GPR183) is a G-protein-coupled receptor that is required for humoral immune responses; polymorphisms in the receptor have been associated with inflammatory autoimmune diseases. The natural ligand for EBI2 has been unknown. Here we describe the identification of 7α,25-dihydroxycholesterol (also called 7α,25-OHC or 5-cholesten-3β,7α,25-triol) as a potent and selective agonist of EBI2. Functional activation of human EBI2 by 7α,25-OHC and closely related oxysterols was verified by monitoring second messenger readouts and saturable, high-affinity radioligand binding. Furthermore, we find that 7α,25-OHC and closely related oxysterols act as chemoattractants for immune cells expressing EBI2 by directing cell migration in vitro and in vivo. A critical enzyme required for the generation of 7α,25-OHC is cholesterol 25-hydroxylase (CH25H). Similar to EBI2 receptor knockout mice, mice deficient in CH25H fail to position activated B cells within the spleen to the outer follicle and mount a reduced plasma cell response after an immune challenge. This demonstrates that CH25H generates EBI2 biological activity in vivo and indicates that the EBI2-oxysterol signalling pathway has an important role in the adaptive immune response. 相似文献
78.
Dawson MA Prinjha RK Dittmann A Giotopoulos G Bantscheff M Chan WI Robson SC Chung CW Hopf C Savitski MM Huthmacher C Gudgin E Lugo D Beinke S Chapman TD Roberts EJ Soden PE Auger KR Mirguet O Doehner K Delwel R Burnett AK Jeffrey P Drewes G Lee K Huntly BJ Kouzarides T 《Nature》2011,478(7370):529-533
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A SUMOylation-defective MITF germline mutation predisposes to melanoma and renal carcinoma 总被引:1,自引:0,他引:1
Bertolotto C Lesueur F Giuliano S Strub T de Lichy M Bille K Dessen P d'Hayer B Mohamdi H Remenieras A Maubec E de la Fouchardière A Molinié V Vabres P Dalle S Poulalhon N Martin-Denavit T Thomas L Andry-Benzaquen P Dupin N Boitier F Rossi A Perrot JL Labeille B Robert C Escudier B Caron O Brugières L Saule S Gardie B Gad S Richard S Couturier J Teh BT Ghiorzo P Pastorino L Puig S Badenas C Olsson H Ingvar C Rouleau E Lidereau R Bahadoran P Vielh P Corda E Blanché H Zelenika D 《Nature》2011,480(7375):94-98