Visual monitoring of water deficit stress using infra-red thermography in wheat

Item does not contain fulltex

The SARS-coronavirus nsp7+nsp8 complex is a unique multimeric RNA polymerase capable of both de novo initiation and primer extension

Uniquely among RNA viruses, replication of the ∼30-kb SARS-coronavirus genome is believed to involve two RNA-dependent RNA polymerase (RdRp) activities. The first is primer-dependent and associated with the 106-kDa non-structural protein 12 (nsp12), whereas the second is catalysed by the 22-kDa nsp8. This latter enzyme is capable of de novo initiation and has been proposed to operate as a primase. Interestingly, this protein has only been crystallized together with the 10-kDa nsp7, forming a hexadecameric, dsRNA-encircling ring structure [i.e. nsp(7+8), consisting of 8 copies of both nsps]. To better understand the implications of these structural characteristics for nsp8-driven RNA synthesis, we studied the prerequisites for the formation of the nsp(7+8) complex and its polymerase activity. We found that in particular the exposure of nsp8's natural N-terminal residue was paramount for both the protein's ability to associate with nsp7 and for boosting its RdRp activity. Moreover, this ‘improved’ recombinant nsp8 was capable of extending primed RNA templates, a property that had gone unnoticed thus far. The latter activity is, however, ∼20-fold weaker than that of the primer-dependent nsp12-RdRp at equal monomer concentrations. Finally, site-directed mutagenesis of conserved D/ExD/E motifs was employed to identify residues crucial for nsp(7+8) RdRp activity

Magnetic Structure in Fe/Sm-Co Exchange Spring Bilayers with Intermixed Interfaces

The depth profile of the intrinsic magnetic properties in an Fe/Sm-Co bilayer fabricated under nearly optimal spring-magnet conditions was determined by complementary studies of polarized neutron reflectometry and micromagnetic simulations. We found that at the Fe/Sm-Co interface the magnetic properties change gradually at the length scale of 8 nm. In this intermixed interfacial region, the saturation magnetization and magnetic anisotropy are lower and the exchange stiffness is higher than values estimated from the model based on a mixture of Fe and Sm-Co phases. Therefore, the intermixed interface yields superior exchange coupling between the Fe and Sm-Co layers, but at the cost of average magnetization.Comment: 16 pages, 6 figures and 1 tabl

The mechanism of resistance to favipiravir in influenza.

Favipiravir is a broad-spectrum antiviral that has shown promise in treatment of influenza virus infections. While emergence of resistance has been observed for many antiinfluenza drugs, to date, clinical trials and laboratory studies of favipiravir have not yielded resistant viruses. Here we show evolution of resistance to favipiravir in the pandemic H1N1 influenza A virus in a laboratory setting. We found that two mutations were required for robust resistance to favipiravir. We demonstrate that a K229R mutation in motif F of the PB1 subunit of the influenza virus RNA-dependent RNA polymerase (RdRP) confers resistance to favipiravir in vitro and in cell culture. This mutation has a cost to viral fitness, but fitness can be restored by a P653L mutation in the PA subunit of the polymerase. K229R also conferred favipiravir resistance to RNA polymerases of other influenza A virus strains, and its location within a highly conserved structural feature of the RdRP suggests that other RNA viruses might also acquire resistance through mutations in motif F. The mutations identified here could be used to screen influenza virus-infected patients treated with favipiravir for the emergence of resistance

Ferromagnetic Domain Distribution in Thin Films During Magnetization Reversal

We have shown that polarized neutron reflectometry can determine in a model-free way not only the mean magnetization of a ferromagnetic thin film at any point of a hysteresis cycle, but also the mean square dispersion of the magnetization vectors of its lateral domains. This technique is applied to elucidate the mechanism of the magnetization reversal of an exchange-biased Co/CoO bilayer. The reversal process above the blocking temperature is governed by uniaxial domain switching, while below the blocking temperature the reversal of magnetization for the trained sample takes place with substantial domain rotation

The RNA polymerase activity of SARS-coronavirus nsp12 is primer dependent

An RNA-dependent RNA polymerase (RdRp) is the central catalytic subunit of the RNA-synthesizing machinery of all positive-strand RNA viruses. Usually, RdRp domains are readily identifiable by comparative sequence analysis, but biochemical confirmation and characterization can be hampered by intrinsic protein properties and technical complications. It is presumed that replication and transcription of the approximately 30-kb severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) RNA genome are catalyzed by an RdRp domain in the C-terminal part of nonstructural protein 12 (nsp12), one of 16 replicase subunits. However, thus far full-length nsp12 has proven refractory to expression in bacterial systems, which has hindered both the biochemical characterization of coronavirus RNA synthesis and RdRp-targeted antiviral drug design. Here, we describe a combined strategy involving bacterial expression of an nsp12 fusion protein and its in vivo cleavage to generate and purify stable SARS-CoV nsp12 (106 kDa) with a natural N-terminus and C-terminal hexahistidine tag. This recombinant protein possesses robust in vitro RdRp activity, as well as a significant DNA-dependent activity that may facilitate future inhibitor studies. The SARS-CoV nsp12 is primer dependent on both homo- and heteropolymeric templates, supporting the likeliness of a close enzymatic collaboration with the intriguing RNA primase activity that was recently proposed for coronavirus nsp8

Suppressed magnetization in La0.7_{0.7}Ca0.3_{0.3}MnO3_3/YBa2_2Cu3_3O7−δ_{7-\delta} superlattices

We studied the magnetic properties of La$_{0.7}$Ca$_{0.3}$MnO$_3$ / YBa$_2$Cu$_3$O$_{7-\delta}$ superlattices. Magnetometry showed that with increasing YBa$_2$Cu$_3$O$_{7-\delta}$ layer thickness the saturation magnetization per La$_{0.7}$Ca$_{0.3}$MnO$_3$ layer decreases. From polarized neutron reflectometry we determined that this magnetization reduction is due to an inhomogenous magnetization depth profile arising from the suppression of magnetization near the La$_{0.7}$Ca$_{0.3}$MnO$_3$ / YBa$_2$Cu$_3$O$_{7-\delta}$ interface. Electron energy loss spectroscopy indicates an increased 3d band occupation of the Mn atoms in the La$_{0.7}$Ca$_{0.3}$MnO$_3$ layers at the interface. Thus, the suppression of ferromagnetic order at the La$_{0.7}$Ca$_{0.3}$MnO$_3$ / YBa$_2$Cu$_3$O$_{7-\delta}$ interface is most likely due to charge transfer between the two materials.Comment: 4 pages, 4 figures, submitted to Phys. Rev.