How advances in cryo-electron tomography have contributed to our current view of bacterial cell biology

Microbial Biotechnolog

Structural Analysis of a Nitrogenase Iron Protein from Methanosarcina acetivorans: Implications for CO2 Capture by a Surface-Exposed [Fe4S4] Cluster.

Nitrogenase iron (Fe) proteins reduce CO2 to CO and/or hydrocarbons under ambient conditions. Here, we report a 2.4-Å crystal structure of the Fe protein from Methanosarcina acetivorans (MaNifH), which is generated in the presence of a reductant, dithionite, and an alternative CO2 source, bicarbonate. Structural analysis of this methanogen Fe protein species suggests that CO2 is possibly captured in an unactivated, linear conformation near the [Fe4S4] cluster of MaNifH by a conserved arginine (Arg) pair in a concerted and, possibly, asymmetric manner. Density functional theory calculations and mutational analyses provide further support for the capture of CO2 on MaNifH while suggesting a possible role of Arg in the initial coordination of CO2 via hydrogen bonding and electrostatic interactions. These results provide a useful framework for further mechanistic investigations of CO2 activation by a surface-exposed [Fe4S4] cluster, which may facilitate future development of FeS catalysts for ambient conversion of CO2 into valuable chemical commodities.IMPORTANCE This work reports the crystal structure of a previously uncharacterized Fe protein from a methanogenic organism, which provides important insights into the structural properties of the less-characterized, yet highly interesting archaeal nitrogenase enzymes. Moreover, the structure-derived implications for CO2 capture by a surface-exposed [Fe4S4] cluster point to the possibility of developing novel strategies for CO2 sequestration while providing the initial insights into the unique mechanism of FeS-based CO2 activation

Reversible and Irreversible Interactions of Poly(3-hexylthiophene) with Oxygen Studied by Spin-Sensitive Methods

Understanding of degradation mechanisms in polymer:fullerene bulk-heterojunctions on the microscopic level aimed at improving their intrinsic stability is crucial for the breakthrough of organic photovoltaics. These materials are vulnerable to exposure to light and/or oxygen, hence they involve electronic excitations. To unambiguously probe the excited states of various multiplicities and their reactions with oxygen, we applied combined magneto-optical methods based on multifrequency (9 and 275 GHz) electron paramagnetic resonance (EPR), photoluminescence (PL), and PL-detected magnetic resonance (PLDMR) to the conjugated polymer poly(3-hexylthiophene) (P3HT) and polymer:fullerene bulk heterojunctions (P3HT:PCBM; PCBM = [6,6]-phenyl-C61-butyric acid methyl ester). We identified two distinct photochemical reaction routes, one being fully reversible and related to the formation of polymer:oxygen charge transfer complexes, the other one, irreversible, being related to the formation of singlet oxygen under participation of bound triplet excitons on the polymer chain. With respect to the blends, we discuss the protective effect of the methanofullerenes on the conjugated polymer bypassing the triplet exciton generation

Increased susceptibility of Trpv4 -deficient mice to obesity and obesity-induced osteoarthritis with very high-fat diet

To test the hypotheses that: 1) the transient receptor potential vanilloid 4 (TRPV4) ion channel is protective in the obesity-model of osteoarthritis (OA), resulting in more severe obesity-induced OA in Trpv4 knockout (Trpv4−/−) mice; and 2) loss of TRPV4 alters mesodermal stem cell differentiation

Gonadal Malformations in Whitefish from Lake Thun: Defining the Case and Evaluating the Role of EDCs

The objectives of this project were to evaluate i) whether the gonad alterations of whitefish (Coregonus lavaretus spp.) in Lake Thun represent abnormal morphological variations specific to this lake, and, if so, ii) whether the malformations are related to chemical exposure, in particular to exposure to endocrine-disrupting compounds (EDCs). Large-scale monitoring data revealed that, although whitefish in other lakes display some background variation of gonad morphology, the situation in Lake Thun, is unique because of the significantly higher prevalence of gonad malformations. The abnormal variations of whitefish gonad morphology include aplasias, compartmentations, fusions, and intersex. In the search for the factor(s) causing the gonad malformations, coregonids were exposed from fertilization up to maturity to Lake Thun water and plankton or to contaminants possibly being present in the lake, including trinitrotoluenes, and naphtalene sulfonates. Since these experiments are still ongoing, a conclusive answer cannot be given yet, but initial observations point to a role of the lake plankton. The possible presence of EDCs in Lake Thun was assessed using bioanalytics and biomarkers. The bioanalytical studies found estrogenic activities in concentrated plankton extracts of Lake Thun, however, estrogenic activities occurred also in plankton extracts of reference lakes. Bioassay-directed fractionation of the plankton samples points to degradation products of natural substances as a cause of the estrogenic activity. Examination of Lake Thun whitefish for EDC biomarkers such as vitellogenin, sex steroid levels or intersex frequency yielded no indications of exposure to EDCs, neither in fish with normal nor in fish with abnormal gonad morphology. Long-term laboratory exposure of developing coregonids to the prototype estrogenic compound, 17?-estradiol, resulted in an increased frequency of intersex gonads, but did not induce the other gonad malformations typical for Lake Thun coregonids. In summing up, the currently available evidence does not support an EDC or chemical etiology of the gonad malformations, however, this preliminary conclusion needs to be substantiated in the ongoing investigations. The project also highlights the need for more detailed knowledge of natural variation in wildlife populations to be able to recognize anthropogenically caused variation

Component-Based Real-Time Operating System for Embedded Applications

Acceptance rate: 37%, Rank (CORE): AInternational audienceAs embedded systems must constantly integrate new functionalities, their developement cycles must be based on high-level abstractions, making the software design more flexible. CBSE provides an approach to these new requirements. However, low-level services provided by operating systems are an integral part of embedded applications, furthermore deployed on resource-limited devices. Therefore, the expected benefits of CBSE must not impact on the constraints imposed by the targetted domain, such as memory footprint, energy consumption, and execution time. In this paper, we present the componentization of a legacy industry-established Real-Time Operating System, and how component-based applications are built on top of it. We use the Think framework that allows to produce flexible systems while paying for flexibility only where desired. Performed experimentions show that the induced overhead is negligeable

TRPV3 and TRPV4 ion channels are not major contributors to mouse heat sensation

<p>Abstract</p> <p>Background</p> <p>The discovery of heat-sensitive Transient Receptor Potential Vanilloid (TRPV) ion channels provided a potential molecular explanation for the perception of innocuous and noxious heat stimuli. TRPV1 has a significant role in acute heat nociception and inflammatory heat hyperalgesia. Yet, substantial innocuous and noxious heat sensitivity remains in TRPV1 knockout animals. Here we investigated the role of two related channels, TRPV3 and TRPV4, in these capacities. We studied TRPV3 knockout animals on both C57BL6 and 129S6 backgrounds, as well as animals deficient in both TRPV3 and TRPV4 on a C57BL6 background. Additionally, we assessed the contributions of TRPV3 and TRPV4 to acute heat nociception and inflammatory heat hyperalgesia during inhibition of TRPV1.</p> <p>Results</p> <p>TRPV3 knockout mice on the C57BL6 background exhibited no obvious alterations in thermal preference behavior. On the 129S6 background, absence of TRPV3 resulted in a more restrictive range of occupancy centered around cooler floor temperatures. TRPV3 knockout mice showed no deficits in acute heat nociception on either background. Mice deficient in both TRPV3 and TRPV4 on a C57BL6 background showed thermal preference behavior similar to wild-type controls on the thermal gradient, and little or no change in acute heat nociception or inflammatory heat hyperalgesia. Masking of TRPV1 by the TRPV1 antagonist JNJ-17203212 did not reveal differences between C57BL6 animals deficient in TRPV3 and TRPV4, compared to their wild-type counterparts.</p> <p>Conclusions</p> <p>Our results support the notion that TRPV3 and TRPV4 likely make limited and strain-dependent contributions to innocuous warm temperature perception or noxious heat sensation, even when TRPV1 is masked. These findings imply the existence of other significant mechanisms for heat perception.</p

TRPV4-Mediated Calcium Influx into Human Bronchial Epithelia upon Exposure to Diesel Exhaust Particles

BACKGROUND: Human respiratory epithelia function in airway mucociliary clearance and barrier function and have recently been implicated in sensory functions. OBJECTIVE: We investigated a link between chronic obstructive pulmonary disease (COPD) pathogenesis and molecular mechanisms underlying Ca2+ influx into human airway epithelia elicited by diesel exhaust particles (DEP). METHODS AND RESULTS: Using primary cultures of human respiratory epithelial (HRE) cells, we determined that these cells possess proteolytic signaling machinery, whereby proteinase-activated receptor-2 (PAR-2) activates Ca2+-permeable TRPV4, which leads to activation of human respiratory disease-enhancing matrix metalloproteinase-1 (MMP-1), a signaling cascade initiated by diesel exhaust particles (DEP), a globally relevant air pollutant. Moreover, we observed ciliary expression of PAR-2, TRPV4, and phospholipase-Cβ3 in human airway epithelia and their DEP-enhanced protein-protein complex formation. We also found that the chronic obstructive pulmonary disease (COPD)-predisposing TRPV4P19S variant enhances Ca2+ influx and MMP 1 activation, providing mechanistic linkage between man-made air pollution and human airway disease. CONCLUSION: DEP evoked protracted Ca2+ influx via TRPV4, enhanced by the COPD-predisposing human genetic polymorphism TRPV4P19S. This mechanism reprograms maladaptive inflammatory and extracellular-matrix-remodeling responses in human airways. The novel concept of air pollution-responsive ciliary signal transduction from PAR-2 to TRPV4 in human respiratory epithelia will accelerate rationally targeted therapies, possibly via the inhalatory route

A synthetic mechanogenetic gene circuit for autonomous drug delivery in engineered tissues

Mechanobiologic signals regulate cellular responses under physiologic and pathologic conditions. Using synthetic biology and tissue engineering, we developed a mechanically responsive bioartificial tissue that responds to mechanical loading to produce a preprogrammed therapeutic biologic drug. By deconstructing the signaling networks induced by activation of the mechanically sensitive ion channel transient receptor potential vanilloid 4 (TRPV4), we created synthetic TRPV4-responsive genetic circuits in chondrocytes. We engineered these cells into living tissues that respond to mechanical loading by producing the anti-inflammatory biologic drug interleukin-1 receptor antagonist. Chondrocyte TRPV4 is activated by osmotic loading and not by direct cellular deformation, suggesting that tissue loading is transduced into an osmotic signal that activates TRPV4. Either osmotic or mechanical loading of tissues transduced with TRPV4-responsive circuits protected constructs from inflammatory degradation by interleukin-1α. This synthetic mechanobiology approach was used to develop a mechanogenetic system to enable long-term, autonomously regulated drug delivery driven by physiologically relevant loading