A trans-acting RNA as a control switch in Escherichia coli: DsrA modulates function by forming alternative structures

DsrA is an 87-nucleotide regulatory RNA of Escherichia coli that acts in trans by RNA–RNA interactions with two different mRNAs, hns and rpoS. DsrA has opposite effects on these transcriptional regulators. H-NS levels decrease, whereas RpoS (σs) levels increase. Here we show that DsrA enhances hns mRNA turnover yet stabilizes rpoS mRNA, either directly or via effects on translation. Computational and RNA footprinting approaches led to a refined structure for DsrA, and a model in which DsrA interacts with the hns mRNA start and stop codon regions to form a coaxial stack. Analogous bipartite interactions exist in eukaryotes, albeit with different regulatory consequences. In contrast, DsrA base pairs in discrete fashion with the rpoS RNA translational operator. Thus, different structural configurations for DsrA lead to opposite regulatory consequences for target RNAs.

Diskreettiaikainen liukuvan moodin säätö kiinteäoksidipolttokennon DC-tasonnostossa

Huoli ympäristön tilasta ja fossiilisten polttoaineiden hinnan nousu ovat vauhdittaneet tutkimusta uusien energialähteiden löytämiseksi. Polttokennot ovat yksi lupaavimmista tekniikoista etenkin hajautetun energiantuotannon, varavoimalaitosten sekä liikennevälineiden alueella. Polttokenno on tehonlähteenä kuitenkin hyvin epäideaalinen, ja se asettaa tehoelektroniikalle lukuisia erityisvaatimuksia. Polttokennon kytkeminen sähköverkkoon on tavallisesti toteutettu käyttämällä galvaanisesti erottavaa DC/DC hakkuria sekä vaihtosuuntaajaa sarjassa. Polttokennon kulumisen estämiseksi tehoelektroniikalta vaaditaan tarkkaa polttokennon lähtövirran hallintaa. Perinteisesti virran hallinta on toteutettu säätämällä hakkurin tulovirtaa PI (Proportional and Integral) tai PID (Proportional, Integral and Derivative) -säätimellä. Hakkurin epälineaarisuudesta johtuen tällainen ratkaisu ei välttämättä toimi kaukana linearisointipisteestä. Lisäksi perinteiset säätimet ovat herkkiä mallinnusvirheille. Tässä diplomityössä on esitetty polttokennon jännitettä nostavan hakkurin tilayhtälökeskiarvoistusmenetelmään perustuva malli, sekä malliin perustuva diskreettiaikainen integroiva liukuvan moodin säätö. Esitetty säätö on luonteeltaan epälineaarinen ja se soveltuu epälineaaristen ja heikosti tunnettujen järjestelmien säätämiseen.

Sistema de extração de potência (power harvesting) usando transdutores piezelétricos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Regulatory mechanism of the light-activable allosteric switch LOV-TAP for the control of DNA binding: a computer simulation study

The spatio-temporal control of gene expression is fundamental to elucidate cell proliferation and deregulation phenomena in living systems. Novel approaches based on light-sensitive multiprotein complexes have recently been devised, showing promising perspectives for the noninvasive and reversible modulation of the DNA-transcriptional activity in vivo. This has lately been demonstrated in a striking way through the generation of the artificial protein construct light-oxygen-voltage (LOV)-tryptophan-activated protein (TAP), in which the LOV-2-Jα photoswitch of phototropin1 from Avena sativa (AsLOV2-Jα) has been ligated to the tryptophan-repressor (TrpR) protein from Escherichia coli. Although tremendous progress has been achieved on the generation of such protein constructs, a detailed understanding of their functioning as opto-genetical tools is still in its infancy. Here, we elucidate the early stages of the light-induced regulatory mechanism of LOV-TAP at the molecular level, using the noninvasive molecular dynamics simulation technique. More specifically, we find that Cys450-FMN-adduct formation in the AsLOV2-Jα-binding pocket after photoexcitation induces the cleavage of the peripheral Jα-helix from the LOV core, causing a change of its polarity and electrostatic attraction of the photoswitch onto the DNA surface. This goes along with the flexibilization through unfolding of a hairpin-like helix-loop-helix region interlinking the AsLOV2-Jα- and TrpR-domains, ultimately enabling the condensation of LOV-TAP onto the DNA surface. By contrast, in the dark state the AsLOV2-Jα photoswitch remains inactive and exerts a repulsive electrostatic force on the DNA surface. This leads to a distortion of the hairpin region, which finally relieves its tension by causing the disruption of LOV-TAP from the DNA.

Teaching digital control of switch mode power supplier

This paper explains the methodology followed to teach the subject `Digital control of power converters'. This subject belongs to the research master on `Industrial Electronics' of the Universidad Politécnica de Madrid. The subject is composed of several theoretical lessons plus the development of an actual digital control. For that purpose an ad hoc dc-dc converter has been designed and built. The use of this board together with some software tools seems a very powerful way for the students to learn the concepts from the design to the real world

Src, a molecular switch governing gain control of synaptic transmission mediated by N-methyl-d-aspartate receptors

The N-methyl-d-aspartate (NMDA) receptor is a principal subtype of glutamate receptor mediating fast excitatory transmission at synapses in the dorsal horn of the spinal cord and other regions of the central nervous system. NMDA receptors are crucial for the lasting enhancement of synaptic transmission that occurs both physiologically and in pathological conditions such as chronic pain. Over the past several years, evidence has accumulated indicating that the activity of NMDA receptors is regulated by the protein tyrosine kinase, Src. Recently it has been discovered that, by means of up-regulating NMDA receptor function, activation of Src mediates the induction of the lasting enhancement of excitatory transmission known as long-term potentiation in the CA1 region of the hippocampus. Also, Src has been found to amplify the up-regulation of NMDA receptor function that is produced by raising the intracellular concentration of sodium. Sodium concentration increases in neuronal dendrites during high levels of firing activity, which is precisely when Src becomes activated. Therefore, we propose that the boost in NMDA receptor function produced by the coincidence of activating Src and raising intracellular sodium may be important in physiological and pathophysiological enhancement of excitatory transmission in the dorsal horn of the spinal cord and elsewhere in the central nervous system.

Role of LMP1 in immune control of EBV infection

The Epstein-Barr virus (EBV) encoded latent membrane protein (LMP1) plays a crucial role in the long-term persistence of this virus within the cells of the immune system. Not only is this protein critical for the transformation of resting B cells by EBV, it also displays pleiotropic effects on various cellular proteins expressed in the host cell. These include up-regulation of expression of B cell activation antigens, adhesion molecules and various components of the antigen processing pathway. Here we discuss how LMP1 acts like an expression 'switch' which, depending on the stage of EBV infection, manoeuvres various pathways that either modulate the immune system towards or against its survival.

A class B switch-mode assisted linear amplifier

A switch-mode assisted linear amplifier (SMALA) combining a linear (Class B) and a switch-mode (Class D) amplifier is presented. The usual single hysteretic controlled half-bridge current dumping stage is replaced by two parallel buck converter stages, in a parallel voltage controlled topology. These operate independently: one buck converter sources current to assist the upper Class B output device, and a complementary converter sinks current to assist the lower device. This topology lends itself to a novel control approach of a dead-band at low power levels where neither class D amplifier assists, allowing the class B amplifier to supply the load without interference, ensuring high fidelity. A 20 W implementation demonstrates 85% efficiency, with distortion below 0.08% measured across the full audio bandwidth at 15 W. The class D amplifier begins assisting at 2 W, and below this value, the distortion was below 0.03%. Complete circuitry is given, showing the simplicity of the additional class D amplifier and its corresponding control circuitry.

Reconfigurable SiC Embedded Photonic Structures with Self Optical Bias Control

Multilayered heterostructures based on embedded a-Si:H and a-SiC:H p-i-n filters are analyzed from differential voltage design perspective using short- and long-pass filters. The transfer functions characteristics are presented. A numerical simulation is presented to explain the filtering properties of the photonic devices. Several monochromatic pulsed lights, separately (input channels) or in a polychromatic mixture (multiplexed signal) at different bit rates, illuminated the device. Steady-state optical bias is superimposed from the front and the back side. Results show that depending on the wavelength of the external background and impinging side, the device acts either as a short- or a long-pass band filter or as a band-stop filter. Particular attention is given to the amplification coefficient weights, which allow to take into account the wavelength background effects when a band or frequency needs to be filtered or the gate switch, in which optical active filter gates are used to select and filter input signals to specific output ports in wavelength division multiplexing (WDM) communication systems. This nonlinearity provides the possibility for selective removal or addition of wavelengths. A truth table of an encoder that performs 8-to-1 MUX function exemplifies the optoelectronic conversion.

Sistema inalámbrico de control de iluminación

L’objectiu principal del projecte és dissenyar un sistema de control automàtic de il·luminació en un recinte tancat, mitjançant la detecció de presència d’una persona que entra dins del radi d’actuació del sistema. Utilitzant dues plaques amb capacitat de comunicació inalàmbrica es controlaran dos components, un sensor i un actuador. El sensor té la funció de detectar la presència d’una persona per mitjà d’infraroigs, mentre que l’actuador ens proporciona la funcionalitat d’un interruptor amb el qual pogué actuar sobre la llum, encenent-la o apagant-la en funció de l’estat de detecció.

Adaptable pulmonary artery band for late arterial switch procedure in transposition of the great arteries.

BACKGROUND: In late-diagnosed transposition of the great arteries (TGA), the left ventricle (LV) involutes as it pumps against low resistance and needs retraining by applying a pulmonary artery band (PAB) in preparation for an arterial switch operation. We report our experience with a telemetrically adaptable band compared with classic banding. METHODS: Ten patients underwent retraining of the LV, 4 patients with an adaptable band and progressive weekly tightening of the band (group 1) and 6 patients with a traditional band (group 2). RESULTS: Mean weight and age at pulmonary band placement was 5.8 ± 2.36 kg and 11.7 ± 11.1 months for group 1 and 5.0 ± 2.3 kg and 6.4 ± 7.6 months for group 2. Time between palliation and switch procedure was 4.2 months in both groups. Group 1 showed an initial mean pulmonary gradient of 25.5 ± 4.43 mm Hg with a 5% closure of the device. The mean gradient increased with progressive closure to 63.5 ± 9.8 mm Hg at the time of the arterial switch operation. There were no reinterventions or deaths in this group. In group 2, the mean pulmonary gradient increased with growth from 49 ± 21.4 mm Hg to 68.4 ± 7.86 mm Hg at the time of the switch procedure. However, 4 of these patients required reoperations during retraining: 2 needed 1 reoperation and 2 needed 2 reoperations. Two patients died-1 after banding and 1 after the switch operation. CONCLUSIONS: Retraining of the LV by the adaptable device allows precise control of the tightening, avoids repetitive operations, and diminishes morbidity.

Leishmania braziliensis: partial control of experimental infection by interleukin-12 p40 deficient mice

Resistance to infection by Leishmania major has been associated with the development of a Th1 type response that is dependent on the presence of interleukin 12 (IL-12). In this work the involvement of this cytokine in the response to infection by L. braziliensis, a less virulent species in the mouse model, was evaluated. Our results show that while interferon (IFN-g) deficient (-/-) mice inoculated L. braziliensis develop severe uncontrolled lesions, chronic lesions that remained under control up to 12 weeks of infection were observed in IL-12p40 -/- mice. IL 12p40 -/- mice had fewer parasites in their lesions than IFN-g-/- mice. Lymph node cells from IL-12p40 -/- were capable of producing low but consistent levels of IFN-g suggestive of its involvement in parasite control. Furthermore, as opposed to previous reports on L. major-infected animals, no switch to a Th2 response was observed in IL-12p40 -/- infected with L. braziliensis.

Oxidative stress activation of miR-125b is part of the molecular switch for Hailey-Hailey disease manifestation.

Hailey-Hailey disease (HHD) is an autosomal dominant disorder characterized by suprabasal cutaneous cell separation (acantholysis) leading to the development of erosive and oozing skin lesion. Micro RNAs (miRNAs) are endogenous post-transcriptional modulators of gene expression with critical functions in health and disease. Here, we evaluated whether the expression of specific miRNAs may play a role in the pathogenesis of HHD. Here, we report that miRNAs are expressed in a non-random manner in Hailey-Hailey patients. miR-125b appeared a promising candidate for playing a role in HHD manifestation. Both Notch1 and p63 are part of a regulatory signalling whose function is essential for the control of keratinocyte proliferation and differentiation and of note, the expression of both Notch1 and p63 is downregulated in HHD-derived keratinocytes. We found that both Notch1 and p63 expression is strongly suppressed by miR-125b expression. Additionally, we found that miR-125b expression is increased by an oxidative stress-dependent mechanism. Our data suggest that oxidative stress-mediated induction of miR-125b plays a specific role in the pathogenesis of HHD by regulating the expression of factors playing an important role in keratinocyte proliferation and differentiation.