In vitro construction of the COQ metabolon unveils the molecular determinants of coenzyme Q biosynthesis.

Metabolons are protein assemblies that perform a series of reactions in a metabolic pathway. However, the general importance and aptitude of metabolons for enzyme catalysis remain poorly understood. In animals, biosynthesis of coenzyme Q is currently attributed to ten different proteins, with COQ3, COQ4, COQ5, COQ6, COQ7 and COQ9 forming the iconic COQ metabolon.

Investigating the biochemical signatures and physiological roles of the FMO family using molecular phylogeny.

Group B flavin-dependent monooxygenases are employed in swathes of different physiological functions. Despite their collectively large substrate profile, they all harness a flavin-based C4a-(hydro)peroxy intermediate for function. Within this class are the flavin- monooxygenases (FMOs), representing an integral component within the secondary metabolism of all living things - xenobiotic detoxification.

Impact of ancestral sequence reconstruction on mechanistic and structural enzymology.

Ancestral sequence reconstruction (ASR) provides insight into the changes within a protein sequence across evolution. More specifically, it can illustrate how specific amino acid changes give rise to different phenotypes within a protein family. Over the last few decades it has established itself as a powerful technique for revealing molecular common denominators that govern enzyme function.

Evolution of enzyme functionality in the flavin-containing monooxygenases.

Among the molecular mechanisms of adaptation in biology, enzyme functional diversification is indispensable. By allowing organisms to expand their catalytic repertoires and adopt fundamentally different chemistries, animals can harness or eliminate new-found substances and xenobiotics that they are exposed to in new environments. Here, we explore the flavin-containing monooxygenases (FMOs) that are essential for xenobiotic detoxification.

Evolutionary and structural analyses of the NADPH oxidase family in eukaryotes reveal an initial calcium dependency.

Reactive oxygen species are unstable molecules generated by the partial reduction of dioxygen. NADPH oxidases are a ubiquitous family of enzymes devoted to ROS production. They fuel an array of physiological roles in different species and are chemically demanding enzymes requiring FAD, NADPH and heme prosthetic groups in addition to either calcium or a various number of cytosolic mediators for activity.

Ancestral reconstruction of mammalian FMO1 enables structural determination, revealing unique features that explain its catalytic properties.

Mammals rely on the oxidative flavin-containing monooxygenases (FMOs) to detoxify numerous and potentially deleterious xenobiotics; this activity extends to many drugs, giving FMOs high pharmacological relevance. However, our knowledge regarding these membrane-bound enzymes has been greatly impeded by the lack of structural information. We anticipated that ancestral-sequence reconstruction could help us identify protein sequences that are more amenable to structural analysis.

A lonely electron blocks incoming pairs.

Electron bifurcation exploits high energetic states to drive unfavorable single electron reactions and determining the overall mechanism governing these electron transfers represents an arduous task. Using extensive stopped-flow spectroscopy and kinetic simulations, Sucharitakul et al. now explore the bifurcation mechanism of the electron transfer flavoprotein EtfAB from the anaerobic gut bacterium Acidaminococcus fermentans.

Publisher Correction: Ancestral-sequence reconstruction unveils the structural basis of function in mammalian FMOs.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Ancestral-sequence reconstruction unveils the structural basis of function in mammalian FMOs.

Flavin-containing monooxygenases (FMOs) are ubiquitous in all domains of life and metabolize a myriad of xenobiotics, including toxins, pesticides and drugs. However, despite their pharmacological importance, structural information remains bereft. To further our understanding behind their biochemistry and diversity, we used ancestral-sequence reconstruction, kinetic and crystallographic techniques to scrutinize three ancient mammalian FMOs: AncFMO2, AncFMO3-6 and AncFMO5.

Formation of a Copper(II)-Tyrosyl Complex at the Active Site of Lytic Polysaccharide Monooxygenases Following Oxidation by HO.

Hydrogen peroxide is a cosubstrate for the oxidative cleavage of saccharidic substrates by copper-containing lytic polysaccharide monooxygenases (LPMOs). The rate of reaction of LPMOs with hydrogen peroxide is high, but it is accompanied by rapid inactivation of the enzymes, presumably through protein oxidation. Herein, we use UV-vis, CD, XAS, EPR, VT/VH-MCD, and resonance Raman spectroscopies, augmented with mass spectrometry and DFT calculations, to show that the product of reaction of an AA9 LPMO with HO at higher pHs is a singlet Cu(II)-tyrosyl radical species, which is inactive for the oxidation of saccharidic substrates.

Economic impact of tibial plateau leveling osteotomy surgical site infection in dogs.

Objective: To evaluate the economic impact of surgical site infection after tibial plateau leveling osteotomy (TPLO) in dogs.

Study Design: Retrospective study

Study Population: Dogs that had unilateral TPLO and did (n = 32) or did not (controls; 32) develop a surgical site infection.

Methods: Medical and billing records were reviewed to identify postoperative care and costs, which were compared between groups.

Coherent dynamics of a telecom-wavelength entangled photon source.

Quantum networks can interconnect remote quantum information processors, allowing interaction between different architectures and increasing net computational power. Fibre-optic telecommunications technology offers a practical platform for routing weakly interacting photonic qubits, allowing quantum correlations and entanglement to be established between distant nodes. Although entangled photons have been produced at telecommunications wavelengths using spontaneous parametric downconversion in nonlinear media, as system complexity increases their inherent excess photon generation will become limiting.

Narrow emission linewidths of positioned InAs quantum dots grown on pre-patterned GaAs(100) substrates.

We report photoluminescence measurements on a single layer of site-controlled InAs quantum dots (QDs) grown by molecular beam epitaxy (MBE) on pre-patterned GaAs(100) substrates with a 15 nm re-growth buffer separating the dots from the re-growth interface. A process for cleaning the re-growth interface allows us to measure single dot emission linewidths of 80 µeV under non-resonant optical excitation, similar to that observed for self-assembled QDs. The dots reveal excitonic transitions confirmed by power dependence and fine structure splitting measurements.

Playing a computer game during lunch affects fullness, memory for lunch, and later snack intake.

Background: The presence of distracting stimuli during eating increases the meal size and could thereby contribute to overeating and obesity. However, the effects of within-meal distraction on later food intake are less clear.

Objective: We sought to test the hypothesis that distraction inhibits memory encoding for a meal, which, in turn, increases later food intake.

Quantum interference of electrically generated single photons from a quantum dot.

Quantum interference lies at the foundation of many protocols for scalable quantum computing and communication with linear optics. To observe these effects the light source must emit photons that are indistinguishable. From a technological standpoint, it would be beneficial to have electrical control over the emission.

An entangled-light-emitting diode.

An optical quantum computer, powerful enough to solve problems so far intractable using conventional digital logic, requires a large number of entangled photons. At present, entangled-light sources are optically driven with lasers, which are impractical for quantum computing owing to the bulk and complexity of the optics required for large-scale applications. Parametric down-conversion is the most widely used source of entangled light, and has been used to implement non-destructive quantum logic gates.

Bell-inequality violation with a triggered photon-pair source.

Here we demonstrate, for the first time, violation of Bell's inequality using a triggered quantum dot photon-pair source without post-selection. Furthermore, the fidelity to the expected Bell state is increased above 90% using temporal gating to reject photons emitted at times when collection of uncorrelated light is more probable. A direct measurement of a CHSH Bell inequality is made showing a clear violation, highlighting that a quantum dot entangled photon source is suitable for communication exploiting nonlocal quantum correlations.

Anomalous coulomb drag in electron-hole bilayers.

We report Coulomb drag measurements on GaAs-AlGaAs electron-hole bilayers. The two layers are separated by a 10 or 25 nm barrier. Below T approximately 1 K we find two features that a Fermi-liquid picture cannot explain.

Evolution of entanglement between distinguishable light states.

We investigate the evolution of quantum correlations over the lifetime of a multiphoton state. Measurements reveal time-dependent oscillations of the entanglement fidelity for photon pairs created by a single semiconductor quantum dot. The oscillations are attributed to the phase acquired in the intermediate, nondegenerate, exciton-photon state and are consistent with simulations.

Postselective two-photon interference from a continuous nonclassical stream of photons emitted by a quantum dot.

We report an electrically driven semiconductor single-photon source capable of emitting photons with a coherence time of up to 400 ps under fixed bias. It is shown that increasing the injection current causes the coherence time to reduce, and this effect is well explained by the fast modulation of a fluctuating environment. Hong-Ou-Mandel-type two-photon interference using a Mach-Zehnder interferometer is demonstrated using this source to test the indistinguishability of individual photons by postselecting events where two photons collide at a beam splitter.

Coherence of an entangled exciton-photon state.

We study the effect of the exciton fine-structure splitting on the polarization entanglement of photon pairs produced by the biexciton cascade in a quantum dot. Entanglement persists despite separations between the intermediate energy levels of up to 4 microeV. Measurements show that entanglement of the photon pair is robust to the dephasing of the intermediate exciton state responsible for the first-order coherence time of either single photon.

Dendritic cells infected by recombinant modified vaccinia virus Ankara retain immunogenicity in vivo despite in vitro dysfunction.

The administration of recombinant vaccinia virus Ankara (MVA) encoding a CTL epitope (pb9) from a malaria antigen induced activation and maturation of splenic dendritic cells (DCs) in vivo. In contrast, incubation of immature dendritic cells (iDCs) with the MVA, in vitro, resulted in down-regulation of MHC class I molecules and reduced their T-cell stimulatory ability. However, the ability of the infected DC to induce an antigen-specific CTL response, in vivo, remained intact.

Babesia bovis: culture of laboratory-adapted parasite lines and clinical isolates in a chemically defined medium.

Babesiosis caused by Babesia spp. is a disease of both veterinary and human importance. Here, we describe a method to continuously culture laboratory lines and field isolates of Babesia bovis in vitro in a chemically defined medium using (ALBU)MAX II as an alternative to bovine serum.