16 research outputs found
Imaging spontaneous currents in superconducting arrays of pi-junctions
Superconductors separated by a thin tunneling barrier exhibit the Josephson
effect that allows charge transport at zero voltage, typically with no phase
shift between the superconductors in the lowest energy state. Recently,
Josephson junctions with ground state phase shifts of pi proposed by theory
three decades ago have been demonstrated. In superconducting loops,
pi-junctions cause spontaneous circulation of persistent currents in zero
magnetic field, analogous to spin-1/2 systems. Here we image the spontaneous
zero-field currents in superconducting networks of temperature-controlled
pi-junctions with weakly ferromagnetic barriers using a scanning SQUID
microscope. We find an onset of spontaneous supercurrents at the 0-pi
transition temperature of the junctions Tpi = 3 K. We image the currents in
non-uniformly frustrated arrays consisting of cells with even and odd numbers
of pi-junctions. Such arrays are attractive model systems for studying the
exotic phases of the 2D XY-model and achieving scalable adiabatic quantum
computers.Comment: Pre-referee version. Accepted to Nature Physic
Generation and Characterization of Human Single-Chain Antibodies Against Polycyclic Aromatic Hydrocarbons
Adsorption of argon on graphite and graphite with preadsorbed xenon monolayer: Simulation using the Monte Carlo technique
Implementation of superconductor/ferromagnet/ superconductor π-shifters in superconducting digital and quantum circuits
Interplay between Y-box-binding protein 1 (YB-1) and poly(A) binding protein (PABP) in specific regulation of YB-1 mRNA translation
YB-1 is a DNA- and RNA-binding protein that regulates expression of many important genes. Its deficiency or excess may pose threats, including malignant cellular transformation and metastasis, which explains the necessity of strict control over its amount at every level. As we showed previously, the 3′ untranslated region (UTR) of YB-1 mRNA contains a regulatory element specifically binding to YB-1 and PABP (PABPC1). Also, we showed that YB-1 selectively inhibits YB-1 mRNA translation, while PABP stimulates it in a poly(A) tail-independent manner. It was suggested that regulation of YB-1 mRNA translation involves competition between PABP and YB-1 for binding to the regulatory element. Here we offer cogent evidence for this model and add novel details to the mechanism of regulation of YB-1 synthesis. In experiments on regulatory element deletion we showed that it is this element that is responsible for a specific effect of YB-1 and PABP on YB-1 mRNA translation. Mutations eliminating only specific YB-1 affinity for this element suppressed the inhibitory effect of YB-1 and concurrently dramatically decreased the PABP stimulating effect. Mutations reducing only specific PABP affinity for this element, as well as spatial separation of the YB-1- and PABP binding sites, did not affect the YB-1 inhibitory action but completely abolished the positive PABP effect. Together, these results unambiguously prove direct inhibitory action of YB-1 on its mRNA translation, while the positive effect of PABP is realized through displacing YB-1 from the regulatory element