A Nanophotonic Structure Containing Living Photosynthetic Bacteria

Photosynthetic organisms rely on a series of self-assembled nanostructures with tuned electronic energy levels in order to transport energy from where it is collected by photon absorption, to reaction centers where the energy is used to drive chemical reactions. In the photosynthetic bacteria Chlorobaculum tepidum, a member of the green sulfur bacteria family, light is absorbed by large antenna complexes called chlorosomes to create an exciton. The exciton is transferred to a protein baseplate attached to the chlorosome, before migrating through the Fenna-Matthews-Olson complex to the reaction center. Here, it is shown that by placing living Chlorobaculum tepidum bacteria within a photonic microcavity, the strong exciton-photon coupling regime between a confined cavity mode and exciton states of the chlorosome can be accessed, whereby a coherent exchange of energy between the bacteria and cavity mode results in the formation of polariton states. The polaritons have energy distinct from that of the exciton which can be tuned by modifying the energy of the optical modes of the microcavity. It is believed that this is the first demonstration of the modification of energy levels within living biological systems using a photonic structure

Robust, tunable, and high purity triggered single photon source at room temperature using a nitrogen-vacancy defect in diamond in an open microcavity

We report progress in the development of tunable room temperature triggered single photon sources based on single nitrogen-vacancy (NV) centres in nanodiamond coupled to open access optical micro-cavities. The feeding of fluorescence from an NV centre into the cavity mode increases the spectral density of the emission and results in an output stream of triggered single photons with spectral line width of order 1 nm, tunable in the range 640 - 700 nm. We record single photon purities exceeding 96% and estimated device efficiencies up to 3%. We compare performance using plano-concave microcavities with radii of curvature from 25 mu m to 4 mu m and show that up to 17% of the total emission is fed into the TEM00 mode. Pulsed Hanbury-Brown Twiss (HBT) interferometry shows that an improvement in single photon purity is facilitated due to the increased spectral density. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License

A Nanophotonic Structure Containing Living Photosynthetic Bacteria

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Photosynthetic organisms rely on a series of self-assembled nanostructures with tuned electronic energy levels in order to transport energy from where it is collected by photon absorption, to reaction centers where the energy is used to drive chemical reactions. In the photosynthetic bacteria Chlorobaculum tepidum, a member of the green sulfur bacteria family, light is absorbed by large antenna complexes called chlorosomes to create an exciton. The exciton is transferred to a protein baseplate attached to the chlorosome, before migrating through the Fenna–Matthews–Olson complex to the reaction center. Here, it is shown that by placing living Chlorobaculum tepidum bacteria within a photonic microcavity, the strong exciton–photon coupling regime between a confined cavity mode and exciton states of the chlorosome can be accessed, whereby a coherent exchange of energy between the bacteria and cavity mode results in the formation of polariton states. The polaritons have energy distinct from that of the exciton which can be tuned by modifying the energy of the optical modes of the microcavity. It is believed that this is the first demonstration of the modification of energy levels within living biological systems using a photonic structure

Inhibition of Mitochondrial Respiration as a Source of Adaphostin-induced Reactive Oxygen Species and Cytotoxicity

Adaphostin is a dihydroquinone derivative that is undergoing extensive preclinical testing as a potential anticancer drug. Previous studies have suggested that the generation of reactive oxygen species (ROS) plays a critical role in the cytotoxicity of this agent. In this study, we investigated the source of these ROS. Consistent with the known chemical properties of dihydroquinones, adaphostin simultaneously underwent oxidation to the corresponding quinone and generated ROS under aqueous conditions. Interestingly, however, this quinone was not detected in intact cells. Instead, high performance liquid chromatography demonstrated that adaphostin was concentrated by up to 300-fold in cells relative to the extracellular medium and that the highest concentration of adaphostin (3000-fold over extracellular concentrations) was detected in mitochondria. Consistent with a mitochondrial site for adaphostin action, adaphostin-induced ROS production was diminished by >75% in MOLT-4 rho(0) cells, which lack mitochondrial electron transport, relative to parental MOLT-4 cells. In addition, inhibition of oxygen consumption was observed when intact cells were treated with adaphostin. Loading of isolated mitochondria to equivalent adaphostin concentrations caused inhibition of uncoupled oxygen consumption in mitochondria incubated with the complex I substrates pyruvate and malate or the complex II substrate succinate. Further analysis demonstrated that adaphostin had no effect on pyruvate or succinate dehydrogenase activity. Instead, adaphostin inhibited reduced decylubiquinone-induced cytochrome c reduction, identifying complex III as the site of inhibition by this agent. Moreover, adaphostin enhanced the production of ROS by succinate-charged mitochondria. Collectively, these observations demonstrate that mitochondrial respiration rather than direct redox cycling of the hydroquinone moiety is a source of adaphostin-induced ROS and identify complex III as a potential target for antineoplastic agents

Effects of a recombinant gene expression on ColE1-like plasmid segregation in Escherichia coli

<p>Abstract</p> <p>Background</p> <p>Segregation of expression plasmids leads to loss of recombinant DNA from transformed bacterial cells due to the irregular distribution of plasmids between the daughter cells during cell division. Under non-selective conditions this segregational instability results in a heterogeneous population of cells, where the non-productive plasmid-free cells overgrow the plasmid-bearing cells thus decreasing the yield of recombinant protein. Amongst the factors affecting segregational plasmid instability are: the plasmid design, plasmid copy-number, host cell genotype, fermentation conditions etc. This study aims to investigate the influence of transcription and translation on the segregation of recombinant plasmids designed for constitutive gene expression in <it>Escherichia coli </it>LE392 at glucose-limited continuous cultivation. To this end a series of pBR322-based plasmids carrying a synthetic human interferon-gamma (hIFNγ) gene placed under the control of different regulatory elements (promoter and ribosome-binding sites) were used as a model.</p> <p>Results</p> <p>Bacterial growth and product formation kinetics of transformed <it>E. coli </it>LE392 cells cultivated continuously were described by a structured kinetic model proposed by Lee et al. (1985). The obtained results demonstrated that both transcription and translation efficiency strongly affected plasmid segregation. The segregation of plasmid having a deleted promoter did not exceed 5% after 190 h of cultivation. The observed high plasmid stability was not related with an increase in the plasmid copy-number. A reverse correlation between the yield of recombinant protein (as modulated by using different ribosome binding sites) and segregational plasmid stability (determined by the above model) was also observed.</p> <p>Conclusions</p> <p>Switching-off transcription of the hIFNγ gene has a stabilising effect on ColE1-like plasmids against segregation, which is not associated with an increase in the plasmid copy-number. The increased constitutive gene expression has a negative effect on segregational plasmid stability. A kinetic model proposed by Lee et al. (1985) was appropriate for description of <it>E. coli </it>cell growth and recombinant product formation in chemostat cultivations.</p

The impact of self-efficacy, alexithymia and multiple traumas on posttraumatic stress disorder and psychiatric co-morbidity following epileptic seizures: A moderated mediation analysis

This study investigated the incidence of posttraumatic stress disorder (PTSD) and psychiatric co-morbidity following epileptic seizure, whether alexithymia mediated the relationship between self-efficacy and psychiatric outcomes, and whether the mediational effect was moderated by the severity of PTSD from other traumas. Seventy-one (M=31, F=40) people with a diagnosis of epilepsy recruited from support groups in the United Kingdom completed the Posttraumatic Stress Diagnostic Scale, the Hospital Anxiety and Depression Scale, the Toronto Alexithymia Scale-20 and the Generalized Self-Efficacy Scale. They were compared with 71 people (M=29, F=42) without epilepsy. For people with epilepsy, 51% and 22% met the diagnostic criteria for post-epileptic seizure PTSD and for PTSD following one other traumatic life event respectively. For the control group, 24% met the diagnostic criteria for PTSD following other traumatic life events. The epilepsy group reported significantly more anxiety and depression than the control. Partial least squares (PLS) analysis showed that self-efficacy was significantly correlated with alexithymia, post-epileptic seizure PTSD and psychiatric co-morbidity. Alexithymia was also significantly correlated with post-epileptic seizure PTSD and psychiatric co-morbidity. Mediation analyses confirmed that alexithymia mediated the path between self-efficacy and post-epileptic seizure PTSD and psychiatric co-morbidity. Moderated mediation also confirmed that self-efficacy and PTSD from one other trauma moderated the effect of alexithymia on outcomes. To conclude, people can develop posttraumatic stress disorder symptoms and psychiatric co-morbidity following epileptic seizure. These psychiatric outcomes are closely linked with their belief in personal competence to deal with stressful situations and regulate their own functioning, to process rather than defend against distressing emotions, and with the degree of PTSD from other traumas. © 2013 Elsevier Ireland Ltd

Valley-addressable polaritons in atomically thin semiconductors

The locking of the electron spin to the valley degree of freedom in transition metal dichalcogenide (TMD) monolayers has seen these materials emerge as a promising platform in valleytronics. When embedded in optical microcavities, the large oscillator strengths of excitonic transitions in TMDs allow the formation of polaritons that are part-light part-matter quasiparticles. Here, we report that polaritons in MoSe2 show an efficient retention of the valley pseudospin contrasting them with excitons and trions in this material. We find that the degree of the valley pseudospin retention is dependent on the photon, exciton and trion fractions in the polariton states. This allows us to conclude that in the polaritonic regime, cavity-modified exciton relaxation inhibits loss of the valley pseudospin. The valley-addressable exciton-polaritons and trion-polaritons presented here offer robust valley-polarized states with the potential for valleytronic devices based on TMDs embedded in photonic structures and valley-dependent nonlinear polariton–polariton interactions

Absorptive capacity and innovation: When is it better to cooperate?

Cooperation can benefit and hurt firms at the same time. An important question then is: when is it better to cooperate? And, once the decision to cooperate is made, how can an appropriate partner be selected? In this paper we present a model of inter-firm cooperation driven by cognitive distance, appropriability conditions and external knowledge. Absorptive capacity of firms develops as an outcome of the interaction between absorptive R&D and cognitive distance from voluntary and involuntary knowledge spillovers. Thus, we offer a revision of the original model by Cohen and Levinthal (Econ J 99(397):569-596, 1989), accounting for recent empirical findings and explicitly modeling absorptive capacity within the framework of interactive learning. We apply that to the analysis of firms' cooperation and R&D investment preferences. The results show that cognitive distance and appropriability conditions between a firm and its cooperation partner have an ambiguous effect on the profit generated by the firm. Thus, a firm chooses to cooperate and selects a partner conditional on the investments in absorptive capacity it is willing to make to solve the understandability/novelty trade-off. © 2014 Springer-Verlag Berlin Heidelberg

Selbstwirksamkeit als Prädiktor eines posttraumatischen Stresssyndroms bei akut traumatisierten Patienten

Post traumatic stress disorder (PTSD) occurs across 15-20% of victims suffering physical injury. The occurrence of PTSD has been attributed to both the trauma and the victim's individual resources, such as resilience, coping strategies, and social support systems. In the present study, we explored the role of self-efficacy for cognitive self-regulation in the posttraumatic adaptation process of sixty-five patients immediately following trauma (T1) and approximately four months later (T2) assessing posttraumatic stress syndrome according to DSM-IV criteria. We hypothesized perceived self-efficacy as a predictor for an increased risk of developing posttraumatic stress symptoms. Self-efficacy measured immediately following trauma correlated significantly with the development of posttraumatic stress syndromes. This finding suggests that the evaluation of cognitive adaptation to trauma is a helpful marker for clinical outcome assessment and can therefore be used for the identification of patients needing psychotherapeutic intervention.Opfer von Unfallereignissen entwickeln in 15-20% die syndromale Symptomatik einer Posttraumatische Belastungsstörung. Für die Entwicklung des Störungsbildes sind neben der Traumaschwere die persönlichen Ressourcen, wie Resilienzfaktoren, Copingstrategien und soziale Unterstützung von zentraler klinischer Bedeutung. Die vorliegende Studie untersuchte die Bedeutung der Selbstwirksamkeit für die kognitive Selbstregulation im posttraumatischen Symptomverlauf anhand der DSM-IV Kriterien bei 65 Patienten unmittelbar nach einem Unfallereignis (T1) und nach 4 Monaten (T2). Entsprechend der Ausgangshypothese bestätigten die Ergebnisse, dass die Selbstwirksamkeit unmittelbar nach dem Unfallereignis eine prädiktive Bedeutung für die Symptomausprägung zum Zeitpunkt T2 nach 4 Monaten hat. Die Studienergebnisse unterstreichen die klinische Bedeutung kognitiver Verlaufsvariablen als hilfreiche Screeningmarker zur Identifizierung von Risikopatienten, die im posttraumatischen Adaptationsprozess einer psychotherapeutischen Intervention bedürfen