- Institute of Biophysics
Biological Research Centre
Temesvári krt. 62
6726 Szeged
Hungary
- Biophysics, Biomembranes, Enzymology, Spectroscopy, Electron Paramagnetic Resonance Spectroscopy, Free Radicals, and 15 moreMembrane transport proteins, Molecular modeling, Psychoacoustics, Protein Folding, Electronic Transport In Molecules, Structural Biology, Fluorescence Spectroscopy, Infrared spectroscopy, Calorimetry, Computer Programming, Machine Learning, Biochemistry and cell biology, Biochemistry and Biotechnology, Acoustics, and Sound and Music Engineeringedit
- I graduated in Physics, specialised into Biophysics. For one and half decades I was primarily an electron paramagneti... moreI graduated in Physics, specialised into Biophysics. For one and half decades I was primarily an electron paramagnetic resonance (EPR) spectroscopist studying spin-labelled membranes and proteins and free radical reactions. In 1999 I became a group leader and extended my researcher profile to a more general interest in biophysics of biomembranes and membrane transport proteins, and with other techniques such as fluorescence and infrared spectroscopy, calorimetry and molecular modelling. Specific current projects include the rotary mechanism of the vacuolar proton-ATPase, protein folding and structure prediction with machine learning and molecular mechanics, free radicals in native biomembranes, and psychoacoustics.edit
Accumulation of proteins in filter membranes limits the efficiently of filtering technologies for cleaning wastewater. Efforts are ongoing to coat commercial filters with different materials (such as titanium-dioxide, TiO2) in order to... more
Accumulation of proteins in filter membranes limits the efficiently of filtering technologies for cleaning wastewater. Efforts are ongoing to coat commercial filters with different materials (such as titanium-dioxide, TiO2) in order to reduce the fouling of the membrane. Beyond monitoring the desired effect of retention of biomolecules, it is demanding to understand what are the biophysical changes in water-soluble proteins caused by interacting with the new coated filter membranes, an aspect that has received little attention so far. Using spin label electron paramagnetic resonance (EPR), aided with native fluorescent spectroscopy and dynamic light scattering (DLS), here we report the changes in the structure and dynamics of bovine serum albumin (BSA) exposed to TiO2 (P25) nanoparticles or passing through commercial polyvinylidene fluoride (PVDF) membranes coated with the same nanoparticles. We have found that the filtering process and prolongued exposure to TiO2 nanoparticles had ...
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Ductins are a family of homologous and structurally similar membrane proteins with 2 or 4 trans-membrane alpha-helices. The active forms of the Ductins are membranous ring-or star-shaped oligomeric assemblies and they provide various... more
Ductins are a family of homologous and structurally similar membrane proteins with 2 or 4 trans-membrane alpha-helices. The active forms of the Ductins are membranous ring-or star-shaped oligomeric assemblies and they provide various pore, channel, gap-junction functions, assist in membrane fusion processes and also serve as the rotor c-ring domain of V-and F-ATPases. All functions of the Ductins have been reported to be sensitive to the presence of certain divalent metal cations (Me 2+), most frequently Cu 2+ or Ca 2+ ions, for most of the better known members of the family, and the mechanism of this effect is not yet known. Given that we have earlier found a prominent Me 2+ binding site in a wellcharacterised Ductin protein, we hypothesise that certain divalent cations can structurally modulate the various functions of Ductin assemblies via affecting their stability by reversible non-covalent binding to them. A fine control of the stability of the assembly ranging from separated monomers through a loosely/weakly to tightly/strongly assembled ring might render precise regulation of Ductin functions possible. The putative role of direct binding of Me 2+ to the c-ring subunit of active ATP hydrolase in autophagy and the mechanism of Ca 2+dependent formation of the mitochondrial permeability transition pore are also discussed.
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The dynamic balance of transcriptional and translational regulation together with degron-controlled proteolysis shapes the ever-changing cellular proteome. While a large variety of degradation signals has been characterized, our knowledge... more
The dynamic balance of transcriptional and translational regulation together with degron-controlled proteolysis shapes the ever-changing cellular proteome. While a large variety of degradation signals has been characterized, our knowledge of cis-acting protein motifs that can in vivo stabilize otherwise short-lived proteins is very limited. We have identified and characterized a conserved 13-mer protein segment derived from the p54/Rpn10 ubiquitin receptor subunit of the Drosophila 26S proteasome, which fulfills all the characteristics of a protein stabilization motif (STABILON). Attachment of STABILON to various intracellular as well as medically relevant secreted model proteins resulted in a significant increase in their cellular or extracellular concentration in mammalian cells. We demonstrate that STABILON acts as a universal and dual function motif that, on the one hand, increases the concentration of the corresponding mRNAs and, on the other hand, prevents the degradation of s...
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Small heat shock proteins (sHSPs) have been demonstrated to interact with lipids and modulate the physical state of membranes across species. Through these interactions, sHSPs contribute to the maintenance of membrane integrity. HSPB1 is... more
Small heat shock proteins (sHSPs) have been demonstrated to interact with lipids and modulate the physical state of membranes across species. Through these interactions, sHSPs contribute to the maintenance of membrane integrity. HSPB1 is a major sHSP in mammals, but its lipid interaction profile has so far been unexplored. In this study, we characterized the interaction between HSPB1 and phospholipids. HSPB1 not only associated with membranes via membrane-forming lipids, but also showed a strong affinity towards highly fluid membranes. It participated in the modulation of the physical properties of the interacting membranes by altering rotational and lateral lipid mobility. In addition, the in vivo expression of HSPB1 greatly affected the phase behavior of the plasma membrane under membrane fluidizing stress conditions. In light of our current findings, we propose a new function for HSPB1 as a membrane chaperone.
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
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The effect of an oscillating electric field generated from music on yeast vacuolar proton-ATPase (V-ATPase) activity in its native environment is reported. An oscillating electric field is generated from audio clips of music spanning... more
The effect of an oscillating electric field generated from music on yeast vacuolar proton-ATPase (V-ATPase) activity in its native environment is reported. An oscillating electric field is generated from audio clips of music spanning various genres and played to electrodes that are immersed into a dispersion of yeast vacuolar membrane vesicles natively hosting a high concentration of active V-ATPase. The substantial difference in the ATP hydrolysing activity of V-ATPase under the most stimulating and inhibiting music is unprecedented. Good correlation is found between changes in ATPase activity of the enzyme and the combined intensity of certain frequency bands of the Fourier spectra of the music clips. Most prominent identified frequencies are harmonically related to each other and to the estimated rotation rate of the enzyme.
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Proline is a versatile plant metabolite, which is produced in large amounts in plants exposed to osmotic and oxidative stress. Proline has been shown to provide protection against various reactive oxygen species (ROS), such as hydrogen... more
Proline is a versatile plant metabolite, which is produced in large amounts in plants exposed to osmotic and oxidative stress. Proline has been shown to provide protection against various reactive oxygen species (ROS), such as hydrogen peroxide and hydroxyl radicals. On the other hand, its protective effect against singlet oxygen has been debated, and it is considered ineffective against superoxide. Here we used various methods for the detection of singlet oxygen (electron paramagnetic resonance, EPR, spin trapping by 2,2,6,6-tetramethyl-4-piperidone, fluorescence probing by singlet oxygen sensor green, SOSG, and oxygen uptake due to chemical trapping) and superoxide (oxygen uptake due to oxygen reduction) in vitro and in isolated thylakoids. We demonstrated that proline does quench both singlet oxygen and superoxide in vitro.
Autophagy, the process of cellular self-degradation, is intrinsically tied to the degradative function of the lysosome. Several diseases have been linked to lysosomal degradative defects, including rare lysosomal storage disorders and... more
Autophagy, the process of cellular self-degradation, is intrinsically tied to the degradative function of the lysosome. Several diseases have been linked to lysosomal degradative defects, including rare lysosomal storage disorders and neurodegenerative diseases. Ion channels and pumps play a major regulatory role in autophagy. Importantly, calcium signaling produced by TRPML1 (transient receptor potential cation channel, mucolipin subfamily) has been shown to regulate autophagic progression through biogenesis of autophagic-lysosomal organelles, activation of mTORC1 (mechanistic target of rapamycin complex 1) and degradation of autophagic cargo. ER calcium channels such as IP3Rs supply calcium for the lysosome, and lysosomal function is severely disrupted in the absence of lysosomal calcium replenishment by the ER. TRPML1 function is also regulated by LC3 (microtubule-associated protein light chain 3) and mTORC1, two critical components of the autophagic network. Here we provide an overview of the current knowledge about ion channels and pumps-including lysosomal V-ATPase (vacuolar proton-ATPase), which is required for acidification and hence proper enzymatic activity of lysosomal hydrolases-in the regulation of autophagy, and discuss how functional impairment of some of these leads to diseases.
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Nanoparticles targeting transporters of the blood-brain barrier (BBB) are promising candidates to increase the brain penetration of biopharmacons. Solute carriers (SLC) are expressed at high levels in brain endothelial cells and show a... more
Nanoparticles targeting transporters of the blood-brain barrier (BBB) are promising candidates to increase the brain penetration of biopharmacons. Solute carriers (SLC) are expressed at high levels in brain endothelial cells and show a specific pattern at the BBB. The aim of our study was to test glutathione and ligands of SLC transporters as single or dual BBB targeting molecules for nanovesicles. High mRNA expression levels for hexose and neutral amino acid transporting SLCs were found in isolated rat brain microvessels and our rat primary cell based co-culture BBB model. Niosomes were derivatized with glutathione and SLC ligands glucopyranose and alanine. Serum albumin complexed with Evans blue (67 kDa), which has a very low BBB penetration, was selected as a cargo. The presence of targeting ligands on niosomes, especially dual labeling, increased the uptake of the cargo molecule in cultured brain endothelial cells. This cellular uptake was temperature dependent and could be decr...
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Background The blood-brain barrier restricts drug penetration to the central nervous system. Targeted nanocarriers are new potential tools to increase the brain entry of drugs. Ligands of endogenous transporters of the blood-brain barrier... more
Background The blood-brain barrier restricts drug penetration to the central nervous system. Targeted nanocarriers are new potential tools to increase the brain entry of drugs. Ligands of endogenous transporters of the blood-brain barrier can be used as targeting vectors for brain delivery of nanoparticles. Objective We tested biotin-labeled solid nanoparticles for the first time and compared to biotinylated glutathione-labeled nanoparticles in brain endothelial cells. Method Neutravidin coated fluorescent polystyrene nanoparticles were derivatized with biotin and biotinylated glutathione. As a human in vitro blood-brain barrier model hCMEC/D3 brain endothelial cells were used. Cell viability by MTT test, uptake and transfer of the nanoparticles across the endothelial monolayers were measured. The uptake of the nanoparticles was visualized by confocal microscopy. Results The tested nanoparticles caused no change in cell viability. The uptake of biotin- and glutathione-labeled nanopa...
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Rotary enzymes are complex, highly challenging biomolecular machines whose biochemical working mechanism involves intersubunit rotation. The true intrinsic rate of rotation of any rotary enzyme is not known in a native, unmodified state.... more
Rotary enzymes are complex, highly challenging biomolecular machines whose biochemical working mechanism involves intersubunit rotation. The true intrinsic rate of rotation of any rotary enzyme is not known in a native, unmodified state. Here we use the effect of an oscillating electric (AC) field on the biochemical activity of a rotary enzyme, the vacuolar proton-ATPase (V-ATPase), to directly measure its mean rate of rotation in its native membrane environment, without any genetic, chemical or mechanical modification of the enzyme, for the first time. The results suggest that a transmembrane AC field is able to synchronise the steps of ion-pumping in individual enzymes via a hold-and-release mechanism, which opens up the possibility of biotechnological exploitation. Our approach is likely to work for other transmembrane ion-transporting assemblies, not only rotary enzymes, to determine intrinsic in situ rates of ion pumping.
Histidine-rich tripodal peptides form unique oligonuclear complexes with copper(ii), which exhibit efficient catecholase-like activity.
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Although the physiological regulatory function of the gasotransmitter NO (a diatomic free radical) was discovered decades ago, NO is still in the frontline research in biomedicine. NO has been implicated in a variety of physiological and... more
Although the physiological regulatory function of the gasotransmitter NO (a diatomic free radical) was discovered decades ago, NO is still in the frontline research in biomedicine. NO has been implicated in a variety of physiological and pathological processes; therefore, pharmacological modulation of NO levels in various tissues may have significant therapeutic value. NO is generated by NOS in most of cell types and by non-enzymatic reactions. Measurement of NO is technically difficult due to its rapid chemical reactions with a wide range of molecules, such as, for example, free radicals, metals, thiols, etc. Therefore, there are still several contradictory findings on the role of NO in different biological processes. In this review, we briefly discuss the major techniques suitable for measurement of NO (electron paramagnetic resonance, electrochemistry, fluorometry) and its derivatives in biological samples (nitrite/nitrate, NOS, cGMP, nitrosothiols) and discuss the advantages and...
ABSTRACT
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This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
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The effect of an oscillating electric field generated from music on yeast vacuolar proton-ATPase (V- ATPase) activity in its native environment is reported. An oscillating electric field is generated from audio clips of music spanning... more
The effect of an oscillating electric field generated from music on yeast vacuolar proton-ATPase (V- ATPase) activity in its native environment is reported. An oscillating electric field is generated from audio clips of music spanning various genres and played to electrodes that are immersed into a dispersion of yeast vacuolar membrane vesicles natively hosting a high concentration of active V- ATPase. The substantial difference in the ATP hydrolysing activity of V-ATPase under the most stimulating and inhibiting music is unprecedented. Good correlation is found between changes in the specific activity of the enzyme and the combined intensity of certain frequency bands of the Fourier spectra of the music clips. Most prominent identified frequencies are harmonically related to each other and to the estimated rotation rate of the enzyme. Under the given experimental conditions, the top four music clips that most enhance the specific activity of V-ATPase are in the musical key of D, in...
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Replacement of the normal culture liquid to a nitrate-free medium resulted in an immediate drop in the ratio of protein to lipid in isolated cell envelopes of Anacystis nidulans cells. The relative fluidity of the envelope membranes or... more
Replacement of the normal culture liquid to a nitrate-free medium resulted in an immediate drop in the ratio of protein to lipid in isolated cell envelopes of Anacystis nidulans cells. The relative fluidity of the envelope membranes or liposomes, made from the extracted lipids of the envelope, was estimated by measuring the steady-state fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene. A thermotrophic phase transition of lipids within the cytoplasmic membrane of intact cells was also revealed by detecting the temperature-dependent absorption changes in the proportion of zeaxanthin at 390 nm. It became evident that a decrease in the proportion of protein to lipid within the cell envelope was accompanied neither by changes in the microviscosity level, nor by shifting of characteristic temperatures of the liquid-crystalline-to-gel transition of lipids. In parallel with nitrate starvation, however, the proportion of saturated fatty acids of the envelope lipids increased markedly. Accumulation of saturated, longer-chain (C18) fatty acids at the cost of C16 counterparts upon nitrate deprivation occurred in all of the complex lipids. In accordance with these findings, a pronounced decrease in the fluidity was demonstrated for the liposomes prepared from the envelope polar lipids of nitrate-starved cells compared with the corresponding control, throughout the temperature range (45-5 degrees C) studied. We propose that the fluidizing effect due to a fall in the ratio of protein to lipid was compensated by a rapidly triggering regulatory process which enables the preservation of the fluidity characteristics at an optimal level within the cell envelope of A. nidulans.
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Research Interests: Engineering, Physics, Chemistry, Decision Making, Biology, and 15 moreFluorescent Dyes and Reagents, Medicine, Multidisciplinary, Fluorescence Lifetime, Humans, Cancer Therapy, Laurdan, Heat stress, Microstructures, Heat Shock Proteins, Heat Shock Protein, Electron Paramagnetic Resonance, Membrane Fluidity, Cell Membrane, and fluorescent dyes
Research Interests: Chemistry, Structural Biology, Biology, Biophysical Chemistry, Medicine, and 15 moreEPR Spectroscopy, Biological Sciences, Saccharomyces cerevisiae, Sequence alignment, Animals, Physical sciences, Enzyme, CHEMICAL SCIENCES, Chickens, Molecular weight, Amino Acid Sequence, Bone Resorption, Electron Paramagnetic Resonance, Macrolides, and Molecular Sequence Data
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The effect of an oscillating electric field generated from music on yeast vacuolar proton-ATPase (V-ATPase) activity in its native environment is reported. An oscillating electric field is generated by electrodes that are immersed into a... more
The effect of an oscillating electric field generated from music on yeast vacuolar proton-ATPase (V-ATPase) activity in its native environment is reported. An oscillating electric field is generated by electrodes that are immersed into a dispersion of yeast vacuolar membrane vesicles natively hosting a high concentration of active V-ATPase. The substantial difference in the ATP hydrolysing activity of V-ATPase under the most stimulating and inhibiting music is unprecedented. Since the topic, i.e., an effect of music on biomolecules, is very attractive for non-scientific, esoteric mystification, we provide a rational explanation for the observed new phenomenon. Good correlation is found between changes in the specific activity of the enzyme and the combined intensity of certain frequency bands of the Fourier spectra of the music clips. Most prominent identified frequencies are harmonically related to each other and to the estimated rotation rate of the enzyme. These results lead to t...
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Barley thylakoid membranes were studied with FTIR and EPR spectroscopy. Thylakoids were exposed to elevated temperatures in order to induce structural changes. As temperatures increased through physiological to even higher levels, no... more
Barley thylakoid membranes were studied with FTIR and EPR spectroscopy. Thylakoids were exposed to elevated temperatures in order to induce structural changes. As temperatures increased through physiological to even higher levels, no features changed, but upon heating to above 45 degrees C, the fraction of lipid acyl chain segments with gauche-type vibration increased, accompanied by a sharp drop in the membranous spin probe component. These apparently conflicting observations in fact concur with the formation of an inverted hexagonal (H(II)) phase, supporting its putative role in protecting the photosynthetic machinery in thylakoid membranes against thermally-induced disassembly.
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Non-linear electron spin resonance (EPR) techniques suitable for measuring proximity relationships in membranes are reviewed. These were developed during the past decade in order to measure changes sensitively in the spin-lattice... more
Non-linear electron spin resonance (EPR) techniques suitable for measuring proximity relationships in membranes are reviewed. These were developed during the past decade in order to measure changes sensitively in the spin-lattice relaxation time (T1) of nitroxyl spin labels covalently attached to membrane lipids or proteins. In combination with paramagnetic quenching agents and double spin-labelling, the methods were further developed for distance measurements. Selected examples are given to illustrate different methods, and types of data obtained for both integral and peripheral membrane proteins.
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lateral sclerosis
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... EXAFS SPECTRAL STUDIES. Auteur(s) / Author(s). NAGY L. ; YAMAGUCHI T. ; NOMURA M. ;PALI T. ; OHTAKI H. ; Revue / Journal Title. ACH, models in chemistry ISSN 1217-8969 Source / Source. 1998, vol. 135, n o 1-2, pp. 129-145 [17 page(s)... more
... EXAFS SPECTRAL STUDIES. Auteur(s) / Author(s). NAGY L. ; YAMAGUCHI T. ; NOMURA M. ;PALI T. ; OHTAKI H. ; Revue / Journal Title. ACH, models in chemistry ISSN 1217-8969 Source / Source. 1998, vol. 135, n o 1-2, pp. 129-145 [17 page(s) (article)] Langue / Language. ...
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Excess light causes damage to the photosynthetic apparatus of plants and algae primarily via reactive oxygen species. Singlet oxygen can be formed by interaction of chlorophyll (Chl) triplet states, especially in the Photosystem II... more
Excess light causes damage to the photosynthetic apparatus of plants and algae primarily via reactive oxygen species. Singlet oxygen can be formed by interaction of chlorophyll (Chl) triplet states, especially in the Photosystem II reaction center, with oxygen. Whether Chls in the light-harvesting antenna complexes play direct role in oxidative photodamage is less clear. In this work, light-induced photobleaching of Chls in the major trimeric light-harvesting complex II (LHCII) is investigated in different molecular environments-protein aggregates, embedded in detergent micelles or in reconstituted membranes (proteoliposomes). The effects of intense light treatment were analyzed by absorption and circular dichroism spectroscopy, steady-state and time-resolved fluorescence and EPR spectroscopy. The rate and quantum yield of photobleaching was estimated from the light-induced Chl absorption changes. Photobleaching occurred mainly in Chl a and was accompanied by strong fluorescence quenching of the remaining unbleached Chls. The rate of photobleaching increased by 140% when LHCII was embedded in lipid membranes, compared to detergent-solubilized LHCII. Removing oxygen from the medium or adding antioxidants largely suppressed the bleaching, confirming its oxidative mechanism. Singlet oxygen formation was monitored by EPR spectroscopy using spin traps and spin labels to detect singlet oxygen directly and indirectly, respectively. The quantum yield of Chl a photobleaching in membranes and detergent was found to be 3.4 × 10 −5 and 1.4 × 10 −5 , respectively. These values compare well with the yields of ROS production estimated from spin-trap EPR spectroscopy (around 4 × 10 −5 and 2 × 10 −5). A kinetic model is proposed, quantifying the generation of Chl and carotenoid triplet states and singlet oxygen. The high quantum yield of photobleaching, especially in the lipid membrane, suggest that direct photodamage of the antenna occurs with rates relevant to photoinhibition in vivo. The results represent further evidence that the molecular environment of LHCII has profound impact on its functional characteristics, including, among others, the susceptibility to photodamage.
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Proline is a versatile plant metabolite, which is produced in large amounts in plants exposed to osmotic and oxidative stress. Proline has been shown to provide protection against various reactive oxygen species (ROS), such as hydrogen... more
Proline is a versatile plant metabolite, which is produced in large amounts in plants exposed to osmotic and oxidative stress. Proline has been shown to provide protection against various reactive oxygen species (ROS), such as hydrogen peroxide and hydroxyl radicals. On the other hand, its protective effect against singlet oxygen has been debated, and it is considered ineffective against superoxide. Here we used various methods for the detection of singlet oxygen (electron paramagnetic resonance, EPR, spin trapping by 2,2,6,6-tetramethyl-4-piperidone, fluorescence probing by singlet oxygen sensor green, SOSG, and oxygen uptake due to chemical trapping) and superoxide (oxygen uptake due to oxygen reduction) in vitro and in isolated thylakoids. We demonstrated that proline does quench both singlet oxygen and superoxide in vitro. By comparing the effects of chemical scavengers and physical quenchers, we concluded that proline eliminates singlet oxygen via a physical mechanism, with a bimolecular quenching rate of ca. 1.5-4 10 6 M −1 s −1. Our data also show that proline can eliminate superoxide in vitro in a process that is likely to proceed via an electron transfer reaction. We could also show that proline does quench both singlet oxygen and superoxide produced in isolated thylakoids. The scavenging efficiency of proline is relatively small on a molar basis, but considering its presence in high amounts in plant cells under stress conditions it may provide a physiologically relevant contribution to ROS scav-enging, supplementing other nonenzymatic ROS scavengers of plant cells.
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The effect of enzyme concentration on the H2-uptake and H2-evolving activities of the reversible hydrogenase from Thiocapsa roseopersicina was examined. In the activity range assayed by a spectrophotometric technique the apparent... more
The effect of enzyme concentration on the H2-uptake and H2-evolving activities of the reversible hydrogenase from Thiocapsa roseopersicina was examined. In the activity range assayed by a spectrophotometric technique the apparent H2-uptake specific activity varied greatly with hydrogenase concentration. Study of H2-evolving activity measured by the H2 electrode method and compared with a gas chromatographic assay also indicated that specific activity was highly dependent on enzyme concentration. The results indicate that the widely applied hydrogenase assays give systematically erroneous specific activity values. These assays should be used only for relative measurements and the hydrogenase concentration in the reaction mixture should be kept constant. To make the data from various laboratories comparable the assay parameters should be standardized.
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Research Interests: Chemical Engineering, Fluorescent Dyes and Reagents, Biological Sciences, Physical sciences, Temperature, and 10 moreMembrane Lipids, Time Resolved, Phase transition, Steady state, Temperature Dependence, Time Factors, Fluorescent probes, Biochemistry and cell biology, Molecular Structure, and Liquid Crystalline
Page 1. Chapter 11 Saturation Transfer Spectroscopy of Biological Membranes Derek Marsh,A László I. Horváth,B Tibor Pálib And Vsevolod A. Livshitsc a Max-Planck-Institut für Biophysikalische Chemie, Abteilung Spektroskopie ...
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The rate of lipid lateral diffusion has been investigated by computer simulation of electron spin resonance (ESR) spectra of spin-labelled dimyristoyl phosphatidylcholine (DMPC) vesicles. An optimization method has been developed to fit... more
The rate of lipid lateral diffusion has been investigated by computer simulation of electron spin resonance (ESR) spectra of spin-labelled dimyristoyl phosphatidylcholine (DMPC) vesicles. An optimization method has been developed to fit the experimental spectra to the theoretical ones calculated from the modified Bloch-equations in order to determine frequencies of probe-probe collisions and the lipid lateral diffusion coefficients. The main results of this study are: (i) Due to the sensitivity of our method to the extent of the overlapping of hyperfine spectral lines it is possible to determine the spin exchange contribution to linebroadening. (ii) It is obvious from these computer analyses that over a wide range of temperatures well above the phase transition both static dipolar interaction and dynamic spin exchange make significant contributions to the linebroadening. (iii) Lipid lateral diffusion coefficient in DMPC bilayers at 36 degrees C was (2.3 +/- 0.2) x 10(-11) m2 s-1.
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ABSTRACT
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Non-linear electron spin resonance (EPR) techniques suitable for measuring proximity relationships in membranes are reviewed. These were developed during the past decade in order to measure changes sensitively in the spin-lattice... more
Non-linear electron spin resonance (EPR) techniques suitable for measuring proximity relationships in membranes are reviewed. These were developed during the past decade in order to measure changes sensitively in the spin-lattice relaxation time (T1) of nitroxyl spin labels covalently attached to membrane lipids or proteins. In combination with paramagnetic quenching agents and double spin-labelling, the methods were further developed for distance measurements. Selected examples are given to illustrate different methods, and types of data obtained for both integral and peripheral membrane proteins.
Research Interests:
Accumulation of proteins in filter membranes limits the efficiently of filtering technologies for cleaning wastewater. Efforts are ongoing to coat commercial filters with different materials (such as titanium-dioxide, TiO2) in order to... more
Accumulation of proteins in filter membranes limits the efficiently of filtering technologies for cleaning wastewater. Efforts are ongoing to coat commercial filters with different materials (such as titanium-dioxide, TiO2) in order to reduce the fouling of the membrane. Beyond monitoring the desired effect of retention of biomolecules, it is demanding to understand what are the biophysical changes in water-soluble proteins caused by interacting with the new coated filter membranes, an aspect that has received little attention so far. Using spin label electron paramagnetic resonance (EPR), aided with native fluorescent spectroscopy and dynamic light scattering (DLS), here we report the changes in the structure and dynamics of bovine serum albumin (BSA) exposed to TiO2 (P25) nanoparticles or passing through commercial polyvinylidene fluoride (PVDF) membranes coated with the same nanoparticles. We have found that the filtering process and prolongued exposure to TiO2 nanoparticles had significant effects on different regions of BSA, and denaturation of the protein was not observed, neither with TiO2 nanoparticles nor by pressing through TiO2coated filter membranes.
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The effect of an oscillating electric field generated from music on yeast vacuolar proton-ATPase (V-ATPase) activity in its native environment is reported. An oscillating electric field is generated from audio clips of music spanning... more
The effect of an oscillating electric field generated from music on yeast vacuolar proton-ATPase (V-ATPase) activity in its native environment is reported. An oscillating electric field is generated from audio clips of music spanning various genres and played to electrodes that are immersed into a dispersion of yeast vacuolar membrane vesicles natively hosting a high concentration of active V-ATPase. The substantial difference in the ATP hydrolysing activity of V-ATPase under the most stimulating and inhibiting music is unprecedented. Good correlation is found between changes in the specific activity of the enzyme and the combined intensity of certain frequency bands of the Fourier spectra of the music clips. Most prominent identified frequencies are harmonically related to each other and to the estimated rotation rate of the enzyme. Under the given experimental conditions, the top four music clips that most enhance the specific activity of V-ATPase are in the musical key of D, in a perfect agreement with the Fourier analysis of the clips. 1
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The effect of an oscillating electric field generated from music on yeast vacuolar proton-ATPase (V-ATPase) activity in its native environment is reported. An oscillating electric field is generated from audio clips of music spanning... more
The effect of an oscillating electric field generated from music on yeast vacuolar proton-ATPase (V-ATPase) activity in its native environment is reported. An oscillating electric field is generated from audio clips of music spanning various genres and played to electrodes that are immersed into a dispersion of yeast vacuolar membrane vesicles natively hosting a high concentration of active V-ATPase. The substantial difference in the ATP hydrolysing activity of V-ATPase under the most stimulating and inhibiting music is unprecedented. Good correlation is found between changes in ATPase activity of the enzyme and the combined intensity of certain frequency bands of the Fourier spectra of the music clips. Most prominent identified frequencies are harmonically related to each other and to the estimated rotation rate of the enzyme. 1