86,665 research outputs found
Crucial aminoacids in the F O sector of the F 1 F O -ATP synthase address H + across the inner mitochondrial membrane: molecular implications in mitochondrial dysfunctions
No full textThe eukaryotic F 1 F O -ATP synthase/hydrolase activity is coupled to H + translocation through the inner mitochondrial membrane. According to a recent model, two asymmetric H + half-channels in the a subunit translate a transmembrane vertical H + flux into the rotor rotation required for ATP synthesis/hydrolysis. Along the H + pathway, conserved aminoacid residues, mainly glutamate, address H + both in the downhill and uphill transmembrane movements to synthesize or hydrolyze ATP, respectively. Point mutations responsible for these aminoacid changes affect H + transfer through the membrane and, as a cascade, result in mitochondrial dysfunctions and related pathologies. The involvement of specific aminoacid residues in driving H + along their transmembrane pathway within a subunit, sustained by the literature and calculated data, leads to depict a model consistent with some mitochondrial disorders
Mitochondrial F-type ATP synthase: multiple enzyme functions revealed by the membrane-embedded FO structure
No full textOf the two main sectors of the F-type ATP synthase, the membrane-intrinsic F(O)domain is the one which, during evolution, has undergone the highest structural variations and changes in subunit composition. The F(O)complexity in mitochondria is apparently related to additional enzyme functions that lack in bacterial and thylakoid complexes. Indeed, the F-type ATP synthase has the main bioenergetic role to synthesize ATP by exploiting the electrochemical gradient built by respiratory complexes. The F(O)membrane domain, essential in the enzyme machinery, also participates in the bioenergetic cost of synthesizing ATP and in the formation of thecristae, thus contributing to mitochondrial morphology. The recent enzyme involvement in a high-conductance channel, which forms in the inner mitochondrial membrane and promotes the mitochondrial permeability transition, highlights a new F-type ATP synthase role. Point mutations which cause amino acid substitutions in F(O)subunits produce mitochondrial dysfunctions and lead to severe pathologies. The F(O)variability in different species, pointed out by cryo-EM analysis, mirrors the multiple enzyme functions and opens a new scenario in mitochondrial biology
Selenite ameliorates the ATP hydrolysis of mitochondrial F1FO-ATPase by changing the redox state of thiol groups and impairs the ADP phosphorylation
No full text: Selenite as an inorganic form of selenium can affect the redox state of mitochondria by modifying the thiol groups of cysteines. The F1FO-ATPase has been identified as a mitochondrial target of this compound. Indeed, the bifunctional mechanism of ATP turnover of F1FO-ATPase was differently modified by selenite. The activity of ATP hydrolysis was stimulated, whereas the ADP phosphorylation was inhibited. We ascertain that a possible new protein adduct identified as seleno-dithiol (-S-Se-S-) mercaptoethanol-sensitive caused the activation of F-ATPase activity and the oxidation of free -SH groups in mitochondria. Conversely, the inhibition of ATP synthesis by selenite might be irreversible. The kinetic analysis of the activation mechanism was an uncompetitive mixed type with respect to the ATP substrate. Selenite bound more selectively to the F1FO-ATPase loaded with the substrate by preferentially forming a tertiary (enzyme-ATP-selenite) complex. Otherwise, the selenite was a competitive mixed-type activator with respect to the Mg2+ cofactor. Thus, selenite more specifically bound to the free enzyme forming the complex enzyme-selenite. However, even if the selenite impaired the catalysis of F1FO-ATPase, the mitochondrial permeability transition pore phenomenon was unaffected. Therefore, the reversible energy transduction mechanism of F1FO-ATPase can be oppositely regulated by selenite
Osservazioni preliminari sulla presenza di un feromone sessuale in Poecilus cupreus (L.) (Coleoptera Carabidae)
No full textA Therapeutic Role for the F1FO-ATP Synthase
No full textRecently, the F1FO-ATP synthase, due to its dual role of life enzyme as main adenosine triphosphate (ATP) maker and of death enzyme, as ATP dissipator and putative structural component of the mitochondrial permeability transition pore (mPTP), which triggers cell death, has been increasingly considered as a drug target. Accordingly, the enzyme offers new strategies to counteract the increased antibiotic resistance. The challenge is to find or synthesize compounds able to discriminate between prokaryotic and mitochondrial F1FO-ATP synthase, exploiting subtle structural differences to kill pathogens without affecting the host. From this perspective, the eukaryotic enzyme could also be made refractory to macrolide antibiotics by chemically produced posttranslational modifications. Moreover, because the mitochondrial F1FO-ATPase activity stimulated by Ca2+ instead of by the natural modulator Mg2+ is most likely involved in mPTP formation, effectors preferentially targeting the Ca2+-activated enzyme may modulate the mPTP. If the enzyme involvement in the mPTP is confirmed, Ca2+-ATPase inhibitors may counteract conditions featured by an increased mPTP activity, such as neurodegenerative and cardiovascular diseases and physiological aging. Conversely, mPTP opening could be pharmacologically stimulated to selectively kill unwanted cells. On the basis of recent literature and promising lab findings, the action mechanism of F1 and FO inhibitors is considered. These molecules may act as enzyme modifiers and constitute new drugs to kill pathogens, improve compromised enzyme functions, and limit the deathly enzyme role in pathologies. The enzyme offers a wide spectrum of therapeutic strategies to fight at the molecular level diseases whose treatment is still insufficient or merely symptomatic
Novel Regioselective Synthesis of 1,3,4,5-Tetrasubstituted Pyrazoles and Biochemical Valuation on F1FO-ATPase and Mitochondrial Permeability Transition Pore Formation
No full textAn efficient, eco-compatible, and very cheap method for the construction of fully substituted pyrazoles (Pzs) via eliminative nitrilimine-alkene 1,3-dipolar cycloaddition (ENAC) reaction was developed in excellent yield and high regioselectivity. Enaminones and nitrilimines generated in situ were selected as dipolarophiles and dipoles, respectively. A deep screening of the employed base, solvent, and temperature was carried out to optimize reaction conditions. Recycling tests of ionic liquid were performed, furnishing efficient performance until six cycles. Finally, a plausible mechanism of cycloaddition was proposed. Then, the effect of three different structures of Pzs was evaluated on the F1FO-ATPase activity and mitochondrial permeability transition pore (mPTP) opening. The Pz derivatives’ titration curves of 6a, 6h, and 6o on the F1FO-ATPase showed a reduced activity of 86%, 35%, and 31%, respectively. Enzyme inhibition analysis depicted an uncompetitive mechanism with the typical formation of the tertiary complex enzyme-substrate-inhibitor (ESI). The dissociation constant of the ESI complex (Ki’) in the presence of the 6a had a lower order of magnitude than other Pzs. The pyrazole core might set the specific mechanism of inhibition with the F1FO-ATPase, whereas specific functional groups of Pzs might modulate the binding affinity. The mPTP opening decreased in Pz-treated mitochondria and the Pzs’ inhibitory effect on the mPTP was concentration-dependent with 6a and 6o. Indeed, the mPTP was more efficiently blocked with 0.1 mM 6a than with 1 mM 6a. On the contrary, 1 mM 6o had stronger desensitization of mPTP formation than 0.1 mM 6o. The F1FO-ATPase is a target of Pzs blocking mPTP formation
1,5-Disubstituted-1,2,3-triazoles as inhibitors of the mitochondrial Ca2+ -activated F1 FO -ATP(hydrol)ase and the permeability transition pore
No full textThe mitochondrial permeability transition pore (mPTP), a high-conductance channel triggered by a sudden Ca(2+)concentration increase, is composed of the F1FO-ATPase. Since mPTP opening leads to mitochondrial dysfunction, which is a feature of many diseases, a great pharmacological challenge is to find mPTP modulators. In our study, the effects of two 1,5-disubstituted 1,2,3-triazole derivatives, five-membered heterocycles with three nitrogen atoms in the ring and capable of forming secondary interactions with proteins, were investigated. Compounds3aand3bwere selected among a wide range of structurally related compounds because of their chemical properties and effectiveness in preliminary studies. In swine heart mitochondria, both compounds inhibit Ca2+-activated F1FO-ATPase without affecting F-ATPase activity sustained by the natural cofactor Mg2+. The inhibition is mutually exclusive, probably because of their shared enzyme site, and uncompetitive with respect to the ATP substrate, since they only bind to the enzyme-ATP complex. Both compounds show the same inhibition constant (KMODIFIER LETTER PRIMEi), but compound3ahas a doubled inactivation rate constant compared with compound3b. Moreover, both compounds desensitize mPTP opening without altering mitochondrial respiration. The results strengthen the link between Ca2+-activated F1FO-ATPase and mPTP and suggest that these inhibitors can be pharmacologically exploited to counteract mPTP-related diseases
Design, fabrication and characterization of piezoelectric cantilever MEMS for underwater application
No full textThis work shows a preliminary microfabrication route for a novel directional hydrophone based on a cross-shaped design of piezoelectric cantilevers. A thin layer of aluminum nitride (AlN) using Molybdenum (Mo) thin film as electrodes will be exploited as piezoelectric functional layer for the microfabrication of a cantilever-based ultrasonic micro electro mechanical system (MEMS) hydrophone. A parameterized simulation based on length of these cantilevers between 100 and 1000 μm allowed to set the first resonant mode between 20 kHz and 200 kHz, the desired underwater ultrasonic acoustic range. The microsystem was designed with cantilevers facing each other in a cross configuration in order to have novel MEMS hydrophone with an omnidirectional response. In order to investigate the first resonance frequency mode and displacement measurements, a Laser Doppler Vibrometer was used and good agreement between simulations and experimental results was achieved. Responsivity and directionality measurements of the piezoelectric MEMS cantilevers were performed in water. Maximum sensitivity up to −153 dB with omnidirectional directivity pattern was achieved by fabricated MEMS sensor
Microstructure and Electrical Properties of Novel piezo-optrodes Based on Thin-Film Piezoelectric Aluminium Nitride for Sensing
No full textThin-film piezoelectric materials are currently employed in micro-and nanodevices for energy harvesting and mechanical sensing. The deposition of these functional layers, however, is quite challenging onto non-rigid/non-flat substrates, such as optical fibers (OFs). Besides the recent novel applications of OFs as probes for biosensing and bioactuation, the possibility to combine them with piezoelectric thin films and metallic electrodes can pave the way for the employment of novel opto-electro-mechanical sensors (e.g., waveguides, optical phase modulators, tunable filters, energy harvesters or biosensors). In this work the deposition of a thin-film piezoelectric wurtzite-phase Aluminium Nitride (AlN), sandwiched between molybdenum (Mo) electrodes, on the curved lateral surface of an optical fiber with polymeric cladding, is reported for the first time, without the need of an orientation-promoting interlayer. The material surface properties and morphology are characterized by microscopy techniques. High orientation is demonstrated by SEM, PFM and X-ray diffraction analysis on a flat polymeric control, with a resulting piezoelectric coefficient (d33) of ∼5.4 pm/V, while the surface roughness Rms measured by AFM is 9 ÷ 16 nm. The output mechanical sensing capability of the resulting AlN-based piezo-optrode is investigated through mechanical buckling tests: The peak-To-peak voltage for weakly impulsive loads increases with increasing relative displacements (up to 30%), in the range of 20 ÷ 35 mV. Impedance spectroscopy frequency sweeps (10 kHz-1 MHz, 1 V) demonstrate a sensor capacitance of ∼8 pF, with an electrical Q factor as high as 150. The electrical response in the long-Term period (two months) revealed good reliability and durability
Sensitivity and directivity analysis of piezoelectric ultrasonic cantilever-based mems hydrophone for underwater applications
No full textIn this paper, we report on the characterization of the sensitivity and the directionality of a novel ultrasonic hydrophone fabricated by micro-electro-mechanical systems (MEMS) process, using aluminum nitride (AlN) thin film as piezoelectric functional layer and exploiting a stress-driven design. Hydrophone structure and fabrication consist of four piezoelectric cantilevers in cross configuration, whose first resonant frequency mode in water is designed between 20 kHz and 200 kHz. The MEMS fabricated structures exploit 1 μm and 2 μm thick piezoelectric AlN thin film embedded between two molybdenum electrodes grown by DC magnetron sputtering on silicon (Si) wafer. The 200 nm thick molybdenum electrodes thin layers add a stress-gradient through cantilever thickness, leading to an out-of-plane cantilever bending. A water resistant parylene conformal coating of 1 μm was deposited on each cantilever for waterproof operation. AlN upward bent cantilevers show maximum sensitivity up to −163 dB. The cross configuration of four stress-driven piezoelectric cantilevers, combined with an opportune algorithm for processing all data sensors, permits a finer directionality response of this hydrophone
- …
