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  • 1
    Online Resource
    Online Resource
    Structure of the actin-myosin complex in the presence of ATP.
    Proceedings of the National Academy of Sciences ; 1985
    In:  Proceedings of the National Academy of Sciences Vol. 82, No. 10 ( 1985-05), p. 3247-3251
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 82, No. 10 ( 1985-05), p. 3247-3251
    Abstract: The structure of the complex between actin and myosin subfragment 1 (S1), designated the acto-S1 complex, in the presence of ATP was examined by electron microscopy. This was accomplished by using negative staining to study a complex of S1 covalently crosslinked to actin by the zero-length crosslinker, 1-ethyl-3-[3-(dimethylamino)-propyl]carbodiimide. Two levels of S1 binding were studied, with a molar ratio of crosslinked S1 to total actin of either 20% or 50%. The lower percentage was used to observe individual S1 molecules attached to actin, while the higher percentage was used to look at the overall pattern of S1 decoration of the actin filament. In the absence of ATP, the appearances of both the 20% and 50% crosslinked filaments closely resembled the rigor appearances obtained with noncrosslinked proteins. The arrowheads observed had the conventional structure, and individual S1 molecules were elongated and curved and appeared to make an angle of 45 degrees with the thin filament. Addition of ATP to the crosslinked acto-S1 complex caused a radical change in the structure of the cross-bridges. At both 20 and 170 mM ionic strengths, individual S1 molecules appeared to be attached at variable angles which, in contrast to rigor, did not center on 45 degrees. In addition, the S1 molecules often appeared shorter and fatter than in rigor. The 50% crosslinked acto-S1 preparation no longer showed the arrowhead pattern of S1 decoration but instead appeared to be disordered with little obvious polarity. Control experiments with ADP suggest that these effects were not due simply to a weakening of the binding of S1 to actin in the presence of nucleotide but most likely were ATP-specific. The crosslinked acto-S1 complex, which hydrolyzes ATP at about the same rate as the maximal actin-activated ATPase of S1 (Vmax), is composed of a mixture of states A X M X ATP and A X M X ADP X Pi (in which A = actin and M = myosin), with more than 50% of the crosslinked S-1 occurring in state A X M X ATP. Therefore, it appears that both states A X M X ATP and A X M X A DP X Pi have a very different conformation from the classic arrowhead conformation of the A X M state.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.82.10.3247
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1985
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    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 2
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    Online Resource
    The mechanism of RNA 5′ capping with NAD+, NADH and desphospho-CoA
    Springer Science and Business Media LLC ; 2016
    In:  Nature Vol. 535, No. 7612 ( 2016-7), p. 444-447
    Details
    In: Nature, Springer Science and Business Media LLC, Vol. 535, No. 7612 ( 2016-7), p. 444-447
    Type of Medium: Online Resource
    ISSN: 0028-0836 , 1476-4687
    URL: Article
    DOI: 10.1038/nature18622
    RVK:
    TA 1000
    RVK:
    UA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2016
    detail.hit.zdb_id: 120714-3
    detail.hit.zdb_id: 1413423-8
    SSG: 11
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  • 3
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    Time-crystalline eigenstate order on a quantum processor
    Springer Science and Business Media LLC ; 2022
    In:  Nature Vol. 601, No. 7894 ( 2022-01-27), p. 531-536
    Details
    In: Nature, Springer Science and Business Media LLC, Vol. 601, No. 7894 ( 2022-01-27), p. 531-536
    Abstract: Quantum many-body systems display rich phase structure in their low-temperature equilibrium states 1 . However, much of nature is not in thermal equilibrium. Remarkably, it was recently predicted that out-of-equilibrium systems can exhibit novel dynamical phases 2–8 that may otherwise be forbidden by equilibrium thermodynamics, a paradigmatic example being the discrete time crystal (DTC) 7,9–15 . Concretely, dynamical phases can be defined in periodically driven many-body-localized (MBL) systems via the concept of eigenstate order 7,16,17 . In eigenstate-ordered MBL phases, the entire many-body spectrum exhibits quantum correlations and long-range order, with characteristic signatures in late-time dynamics from all initial states. It is, however, challenging to experimentally distinguish such stable phases from transient phenomena, or from regimes in which the dynamics of a few select states can mask typical behaviour. Here we implement tunable controlled-phase (CPHASE) gates on an array of superconducting qubits to experimentally observe an MBL-DTC and demonstrate its characteristic spatiotemporal response for generic initial states 7,9,10 . Our work employs a time-reversal protocol to quantify the impact of external decoherence, and leverages quantum typicality to circumvent the exponential cost of densely sampling the eigenspectrum. Furthermore, we locate the phase transition out of the DTC with an experimental finite-size analysis. These results establish a scalable approach to studying non-equilibrium phases of matter on quantum processors.
    Type of Medium: Online Resource
    ISSN: 0028-0836 , 1476-4687
    URL: Article
    DOI: 10.1038/s41586-021-04257-w
    RVK:
    TA 1000
    RVK:
    UA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 120714-3
    detail.hit.zdb_id: 1413423-8
    SSG: 11
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  • 4
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    Online Resource
    Exponential suppression of bit or phase errors with cyclic error correction
    Springer Science and Business Media LLC ; 2021
    In:  Nature Vol. 595, No. 7867 ( 2021-07-15), p. 383-387
    Details
    In: Nature, Springer Science and Business Media LLC, Vol. 595, No. 7867 ( 2021-07-15), p. 383-387
    Abstract: Realizing the potential of quantum computing requires sufficiently low logical error rates 1 . Many applications call for error rates as low as 10 −15 (refs. 2–9 ), but state-of-the-art quantum platforms typically have physical error rates near 10 −3 (refs. 10–14 ). Quantum error correction 15–17 promises to bridge this divide by distributing quantum logical information across many physical qubits in such a way that errors can be detected and corrected. Errors on the encoded logical qubit state can be exponentially suppressed as the number of physical qubits grows, provided that the physical error rates are below a certain threshold and stable over the course of a computation. Here we implement one-dimensional repetition codes embedded in a two-dimensional grid of superconducting qubits that demonstrate exponential suppression of bit-flip or phase-flip errors, reducing logical error per round more than 100-fold when increasing the number of qubits from 5 to 21. Crucially, this error suppression is stable over 50 rounds of error correction. We also introduce a method for analysing error correlations with high precision, allowing us to characterize error locality while performing quantum error correction. Finally, we perform error detection with a small logical qubit using the 2D surface code on the same device 18,19 and show that the results from both one- and two-dimensional codes agree with numerical simulations that use a simple depolarizing error model. These experimental demonstrations provide a foundation for building a scalable fault-tolerant quantum computer with superconducting qubits.
    Type of Medium: Online Resource
    ISSN: 0028-0836 , 1476-4687
    URL: Article
    DOI: 10.1038/s41586-021-03588-y
    RVK:
    TA 1000
    RVK:
    UA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 120714-3
    detail.hit.zdb_id: 1413423-8
    SSG: 11
    Location Call Number Limitation Availability
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