The fox Operon from Rhodobacter Strain SW2 Promotes Phototrophic Fe(II) Oxidation in Rhodobacter capsulatus SB1003

Anoxygenic photosynthesis based on Fe(II) is thought to be one of the most ancient forms of metabolism and is hypothesized to represent a transition step in the evolution of oxygenic photosynthesis. However, little is known about the molecular basis of this process because, until recently (Y. Jiao and D. K. Newman, J. Bacteriol. 189:1765-1773, 2007), most phototrophic Fe(II)-oxidizing bacteria have been genetically intractable. In this study, we circumvented this problem by taking a heterologous-complementation approach to identify a three-gene operon (the foxEYZ operon) from Rhodobacter sp. strain SW2 that confers enhanced light-dependent Fe(II) oxidation activity when expressed in its genetically tractable relative Rhodobacter capsulatus SB1003. The first gene in this operon, foxE, encodes a c-type cytochrome with no significant similarity to other known proteins. Expression of foxE alone confers significant light-dependent Fe(II) oxidation activity on SB1003, but maximal activity is achieved when foxE is expressed with the two downstream genes foxY and foxZ. In SW2, the foxE and foxY genes are cotranscribed in the presence of Fe(II) and/or hydrogen, with foxZ being transcribed only in the presence of Fe(II). Sequence analysis predicts that foxY encodes a protein containing the redox cofactor pyrroloquinoline quinone and that foxZ encodes a protein with a transport function. Future biochemical studies will permit the localization and function of the Fox proteins in SW2 to be determined

Renal function, revascularization and risk

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Academic Vocabulary for English Language Learners

The researcher conducted a case study with an eighth-grade beginning English speaker to determine whether inclusion of all components of the SIOP model produced the best results for acquisition of academic vocabulary in the content area of social studies. The researcher conducted a six-week intervention in which the student was instructed using various components of the SIOP model during each two-week session and assessed at the beginning and ending of each two-week session. The researcher found that the student was able to acquire the most new academic vocabulary when it was the only skill explicitly taught. This study raises questions about the best ways to instruct English language learners in academic vocabulary, and whether process and English structure should be focused on simultaneously

Crystallographic studies of the Escherichia coli quinol-fumarate reductase with inhibitors bound to the quinol-binding site

The quinol-fumarate reductase (QFR) respiratory complex of Escherichia coli is a four-subunit integral-membrane complex that catalyzes the final step of anaerobic respiration when fumarate is the terminal electron acceptor. The membrane-soluble redox-active molecule menaquinol (MQH(2)) transfers electrons to QFR by binding directly to the membrane-spanning region. The crystal structure of QFR contains two quinone species, presumably MQH(2), bound to the transmembrane-spanning region. The binding sites for the two quinone molecules are termed Q(P) and Q(D), indicating their positions proximal Q(P)) or distal (Q(D)) to the site of fumarate reduction in the hydrophilic flavoprotein and iron-sulfur protein subunits. It has not been established whether both of these sites are mechanistically significant. Co-crystallization studies of the E. coli QFR with the known quinol-binding site inhibitors 2-heptyl-4-hydroxyquinoline-N-oxide and 2-[1-(p-chlorophenyl)ethyl] 4,6-dinitrophenol establish that both inhibitors block the binding of MQH(2) at the Q(P) site. In the structures with the inhibitor bound at Q(P), no density is observed at Q(D), which suggests that the occupancy of this site can vary and argues against a structurally obligatory role for quinol binding to Q(D). A comparison of the Q(P) site of the E. coli enzyme with quinone-binding sites in other respiratory enzymes shows that an acidic residue is structurally conserved. This acidic residue, Glu-C29, in the E. coli enzyme may act as a proton shuttle from the quinol during enzyme turnover

Utility of B-type natriuretic peptide in predicting medium-term mortality in patients undergoing major non-cardiac surgery

We assessed the ability of pre-operative B-type natriuretic peptide (BNP) levels to predict medium-term mortality in patients undergoing major noncardiac surgery. During a median 654 days follow-up 33 patients from a total cohort of 204 patients (16%) died. The optimal cut-off in this cohort, determined using a receiver operating characteristic curve, was >35pg.mL-1. This was associated with a 3.47-fold increase in the hazard of death (p=0.001) and had a sensitivity of 70% and a specificity of 68% for this outcome. These findings extend recent work demonstrating that BNP levels obtained before major noncardiac surgery can be used to predict peri-operative morbidity, and indicate that they also forecast medium-term mortality.This work was supported by a grant from TENOVUS Scotland. The Health Services Research Unit is core-funded by the Chief Scientists Office of the Scottish Executive Health Department.Peer reviewedAuthor versio

Quantum nature of Gaussian discord : experimental evidence and role of system-environment correlations

L.M. acknowledges Project No. P205/12/0694 of Czech Science Foundation (GACR). N.K. is grateful for the support provided by the A. von Humboldt Foundation. N.Q. and N.K. acknowledge the support from the Scottish Universities Physics Alliance (SUPA) and the Engineering and Physical Sciences Research Council (EPSRC). The project was supported within the framework of the BMBF grant “QuORep” and in the framework of the International Max Planck Partnership (IMPP) with Scottish Universities.We provide experimental evidence of quantum features in bipartite states classified as entirely classical according to a conventional criterion based on the Glauber P function but possessing nonzero Gaussian quantum discord. Their quantum nature is experimentally revealed by acting locally on one part of the discordant state. We experimentally verify and investigate the effect of discord increase under the action of local loss and link it to the entanglement with the environment. Adding an environmental system purifying the state, we unveil the flow of quantum correlations within a global pure system using the Koashi-Winter inequality. For a discordant state generated by splitting a state in which the initial squeezing is destroyed by random displacements, we demonstrate the recovery of entanglement highlighting the role of system-environment correlations.Publisher PDFPeer reviewe

Quantum correlations in continuous variable mixed states : from discord to signatures

This thesis studies continuous variable mixed states with the aim of better understanding the fundamental behaviour of quantum correlations in such states, as well as searching for applications of these correlations. I first investigate the interesting phenomenon of discord increase under local loss and explain the behaviour by considering the non-orthogonality of quantum states. I then explore the counter-intuitive result where entanglement can be created by a passive optical beamsplitter, even if the input states are classical, as long as the input states are part of a larger globally nonclassical system. This result emphasises the importance of global correlations in a quantum state, and I propose an application of this protocol in the form of quantum dense coding. Finally, I develop a quantum digital signature protocol that can be described entirely using the continuous variable formalism. Quantum digital signatures provide a method to ensure the integrity and provenance of a message using quantum states. They follow a similar method to quantum key distribution (QKD), but require less post-processing, which means they can sometimes be implemented over channels that are inappropriate for QKD. The method I propose uses homodyne measurement to verify the signature, unlike previous protocols that use single photon detection. The single photon detection of previous methods is designed to give unambiguous results about the signature, but this comes at the cost of getting no information much of the time. Using homodyne detection has the advantage of giving results all the time, but this means that measurement results always have some ambiguity. I show that, even with this ambiguity, the signature protocol based on homodyne measurement outperforms previous protocols, with the advantage enhanced when technical considerations are included. Therefore this represents an interesting new direction in the search for a practical quantum digital signature scheme