The Experts below are selected from a list of 1611 Experts worldwide ranked by ideXlab platform
Daugelavičius Rimantas - One of the best experts on this subject based on the ideXlab platform.
-
Studies of multidrug efflux pump activity in Lactococcus lactis using ethidium cations
'Wiley', 2020Co-Authors: Mikalayeva Valeryia, Daugelavičius RimantasAbstract:Abstract of special issue: 22nd IUBMB & 37th FEBS Congress, Seville, Spain, September 4-9, 2012Multidrug resistance (MDR) efflux pump is the main reason of bacteria resistance to antibiotics. Lactococcus lactis is very important bacterium in food industry. We used spectrofluorimetric measurments to assay the activity of MDR pumps and to investigate the response of the pumps to cell growth conditions. We used ethidium (Et) as as indicatory compound, which increases its fluorescence because of the binding to DNA. We also used another MDR pump substrate Tetraphenylphosphonium (TPP+ ) as a competitive compound and antibiotic gramicidin D as the cell permeabilizer. In this study we demonstrated that the differences in MDR efflux pump activity depend on the growth conditions (with or without heme source) and the energetic state of cellsBiochemijos katedraVytauto Didžiojo universiteta
-
The peculiarities of Tetraphenylphosphonium and ethidium interaction with Listeria monocytogenes and efficiencies of efflux
'OMICS Publishing Group', 2020Co-Authors: Sakalauskaitė Sandra, Šepetytė Kamilė, Daugelavičius RimantasAbstract:31st Euro global summit and expo on vaccines & vaccination; 4th World congress and exhibition on antibiotics and antibiotic resistance & June 14-16, 2018 Barcelona, Spain: posters & accepted abstractsAntimicrobial resistance is a steadily growing world wide problem. Multidrug resistance efflux pumps play a key role in resistance to antibiotics. Because of these pumps Listeria monocytogenes is a multidrug resistant pathogen, not sensitive to many antimicrobial compounds. It is very important to understand the mechanisms how could we regulate the activity of efflux because L. monocytogenes is an opportunistic foodborne Gram-positive pathogen causing serious human infections. It is not easy to develop new antimicrobial compounds which would not be efflux substrates. In addition, the sides effects of new compounds are unknown. So, the knowledge about the inhibition of antibiotics efflux out of cells could increase the efficiency of treatment. We used potentiometric and fluorescence methods to assay the activity of efflux in L. monocytogenes. We used Tetraphenylphosphonium selective electrode to register the activity of efflux. In parallel, the intensity of ethidium fluorescence was determined. We used inhibitors of different families of efflux pumps, such as chlorpromazine, verapamil, and reserpine. Also we explored the effect of Phe-Arg-β-naphthylamide (PAβN) and 1-(1-Naphthylmethyl) piperazine on these gram-positive bacteria. The aim of our studies was to determine the peculiarities of Tetraphenylphosphonium and ethidium interaction with L. monocytogenes cells and to evaluate the efficiency of efflux inhibition. We determined that all of the used inhibitors increase the accumulation of efflux pumps substrate. In addition, we observed that PAβN and NMP inhibit the efflux of Tetraphenylphosphonium but not ethidium. Accumulation of TPP+ strongly inhibited the intensity of L. monocytogenes respiration while ethidium binding was not interfering with this process. The electrochemical analysis of PAβN binding to L. monocytogenes indicated that bacteria accumulate a large amount of this efflux inhibitorBiochemijos katedraGamtos mokslų fakultetasVytauto Didžiojo universiteta
-
Interaction of ethidium and Tetraphenylphosphonium cations with Salmonella enterica cells
'Elsevier BV', 2020Co-Authors: Mikalayeva Valeryia, Sakalauskaitė Sandra, Daugelavičius RimantasAbstract:This work was supported by Research Q2 Council of Lithuania, funding grant No. MIP-040/2015Background and objective: One of the main causes of bacterial resistance to antimicrobials is multidrug resistance induced by the increased efficiency of the efflux pumps. In this study we analyzed how the conditions of assay affect the efflux of indicator substrates ethidium (Et+) and Tetraphenylphosphonium (TPP+) in Salmonella enterica ser. Typhimurium cells. Impact of the outer membrane permeability barrier, composition and temperature of the medium on accumulation of the indicator compounds also was analyzed. Materials and methods: The fluorescence of Et+ and Nile Red was measured using 96-well plates and a plate reader. In parallel to traditional studies of fluorescence we applied a constructed selective electrode to follow the accumulation of Et+ in S. enterica cells. Simul- taneously with monitoring of Et+ concentration in the cell incubation medium, electrochem- ical measurements of TPP+ accumulation were performed. Furthermore, Et+ and TPP+ were used within the same sample as agents competing for the interaction with the efflux pumps. An inhibitor phenylalanyl-arginyl-b-naphtylamide (PAbN) was applied to evaluate the input of RND-family pumps in the total efflux of these indicator compounds. Results: S. enterica cells with the intact outer membrane (OM) bound very low amounts of Et+ or TPP+. Cells with the permeabilized OM accumulate considerably higher amounts of the indicator compounds at pH 8.0, but only Et+ was considerably accumulated at pH 6.5. At conditions of electrochemical monitoring accumulation of Et+ by the permeabilized cells at 37 8C was considerably faster than at 23 8C, but at the higher temperature most of the cell-accumulated Et+ was extruded back to the medium. The fluorescence of Et+ in suspension of cells incubated in 400 mmol/L Tris buffer was about twice higher compared to 100 mmol/L one. [...]Biochemijos katedraGamtos mokslų fakultetasLietuvos sveikatos mokslų universitetas. Medicinos akademija. Kardiologijos institutasVytauto Didžiojo universiteta
-
Evaluation of the efficiency of synthesized efflux pump inhibitors on salmonella enterica ser. Typhimurium cells
'Wiley', 2020Co-Authors: Sutkuvienė Simona, Mikalayeva Valeryia, Pavan Sylvia, Berti Federico, Daugelavičius RimantasAbstract:Online ISSN: 1747-0285Multidrug efflux pump inhibitors have a great potential as pharmacological agents that increase the drug susceptibility of bacterial pathogens. Our study was focused on the synthesis and evaluation of the efficiency of resistance–nodulation–division (RND) family efflux pump inhibitors. The efficiency of these inhibitors was investigated on Salmonella enterica ser. typhimurium cells using Tetraphenylphosphonium (TPP+) and ethidium cations as the efflux pump substrates. Results of our study indicated that efficiency of the inhibitors depends on the cell outer membrane permeability and method of the assay used. Temperature of the incubation medium and a solvent of the inhibitor used have only minor effect on results of the assayBiochemijos katedraVytauto Didžiojo universiteta
-
Analysis of efflux activity in Listeria monocytogenes cells
2018Co-Authors: Šepetytė Kamilė, Sakalauskaitė Sandra, Daugelavičius RimantasAbstract:Introduction: Listeria monocytogenes is an opportunistic foodborne Gram-positive pathogen causing serious human infections. These bacteria are widely distributed in the environment and are the third most common cause of death from food poisoning. Because of efflux pumps L. monocytogenes is a multidrug resistant pathogen, not sensitive to many antimicrobial compounds, including tetracycline, amoxicillin, benzalkonium chloride. Efflux pumps are membrane transporters which can extrude out of the cells various toxic compounds. Knowledge about the regulation of activity of these pumps could enhance the efficiency of treatment. One of ideas how to control the efflux is to use the pump inhibitors. Aim: To assessthe influence of potential inhibitors on the interaction of L. monocytogenes cells with efflux indicator Tetraphenylphosphonium (TPP+) ions.[...]Biochemijos katedraGamtos mokslų fakultetasVytauto Didžiojo universiteta
Joachim Fuchs - One of the best experts on this subject based on the ideXlab platform.
-
neue selenreiche 1 3 dichalkogenol 2 selone via 4 5 dilithio 1 3 dichalkogenol 2 selone
Journal of Organometallic Chemistry, 1992Co-Authors: Helmut Poleschner, Reiner Radeglia, Joachim FuchsAbstract:Abstract 1,3-Dithiole-2-thione ( 1 ), 1,3-diselenole-2-selone ( 2 ), 1,3-thiaselenole-2-thione ( 3 ), 1,3-dithiole-2-selone ( 4 ), 1,3-diselenole-2-thione ( 5 ) and 1,3-thiaselenole-2-selone ( 6 ) are dilithiated with lithium diisopropyl amide in the 4/5 position, followed by selenation (thiolation) and complexation of the resulting heterocyclic diselenolates (dithiolates) to the zinc bis-chelates (tetrabutylammonium or Tetraphenylphosphonium salts). These zinc complexes react with benzoyl chloride to the corresponding selenole and thiole esters. It is noteworthy that the heterocyclic thiones with one or two ring selenium atoms undergo ring transformation (Dimroth rearrangement) during the lithiation chalcogenation sequence, whilst the thione sulfur and one ring selenium atom change their places: 3 → 1,3-dithiole-2-selone-4,5-diselenolate or dithiolate structure, 5 → 1,3-thiaselenole-2-selone-4,5-diselenolate structure. This observed rearrangement is verified by independent synthetic pathways. The corresponding identical zinc chelates 12 and complex 18 result from the precursors 3 and 4 and 5 and 6 respectively. Trapping experiments support the conclusion that this rearrangement takes place already during lithiation. The zinc chelates and thiole and selenole esters are characterized in detail by IR and above all by 13 C and 77 Se NMR spectroscopy, including NMR shift values of the precursor heterocycles. The X-ray crystal structure determination of bis(Tetraphenylphosphonium)-bis(1,3-thiaselenole-2-selone-4,5-diselenolato) zincate ( 18 ), obtained from 5 , shows the rearrangement of 5 to the 1,3-thiaselenole-2-selone partial structure in 18 .
Lin Zhang - One of the best experts on this subject based on the ideXlab platform.
-
Tetraphenylphosphonium tetrafluoroborate 1 1 1 3 3 3 hexafluoroisopropanol ph4pbf4 hfip effecting epoxide initiated cation olefin polycyclizations
ChemInform, 2016Co-Authors: Yan Tian, Lin ZhangAbstract:The use of an excess amount of Tetraphenylphosphonium tetrafluoroborate in 1,1,1,3,3,3-hexafluoroisopropanol, which can stabilize the intermediate cation in the reaction, efficiently promoted epoxide-initiated cation-olefin polycyclization reactions with broad functional group tolerance and water and oxygen tolerance.
-
Tetraphenylphosphonium Tetrafluoroborate/1,1,1,3,3,3-Hexafluoroisopropanol (Ph4PBF4/HFIP) Effecting Epoxide-Initiated Cation–Olefin Polycyclizations
2016Co-Authors: Yan Tian, Lin ZhangAbstract:The use of an excess amount of Tetraphenylphosphonium tetrafluoroborate in 1,1,1,3,3,3-hexafluoroisopropanol, which can stabilize the intermediate cation in the reaction, efficiently promoted epoxide-initiated cation–olefin polycyclization reactions with broad functional group tolerance and water and oxygen tolerance
Helmut Poleschner - One of the best experts on this subject based on the ideXlab platform.
-
neue selenreiche 1 3 dichalkogenol 2 selone via 4 5 dilithio 1 3 dichalkogenol 2 selone
Journal of Organometallic Chemistry, 1992Co-Authors: Helmut Poleschner, Reiner Radeglia, Joachim FuchsAbstract:Abstract 1,3-Dithiole-2-thione ( 1 ), 1,3-diselenole-2-selone ( 2 ), 1,3-thiaselenole-2-thione ( 3 ), 1,3-dithiole-2-selone ( 4 ), 1,3-diselenole-2-thione ( 5 ) and 1,3-thiaselenole-2-selone ( 6 ) are dilithiated with lithium diisopropyl amide in the 4/5 position, followed by selenation (thiolation) and complexation of the resulting heterocyclic diselenolates (dithiolates) to the zinc bis-chelates (tetrabutylammonium or Tetraphenylphosphonium salts). These zinc complexes react with benzoyl chloride to the corresponding selenole and thiole esters. It is noteworthy that the heterocyclic thiones with one or two ring selenium atoms undergo ring transformation (Dimroth rearrangement) during the lithiation chalcogenation sequence, whilst the thione sulfur and one ring selenium atom change their places: 3 → 1,3-dithiole-2-selone-4,5-diselenolate or dithiolate structure, 5 → 1,3-thiaselenole-2-selone-4,5-diselenolate structure. This observed rearrangement is verified by independent synthetic pathways. The corresponding identical zinc chelates 12 and complex 18 result from the precursors 3 and 4 and 5 and 6 respectively. Trapping experiments support the conclusion that this rearrangement takes place already during lithiation. The zinc chelates and thiole and selenole esters are characterized in detail by IR and above all by 13 C and 77 Se NMR spectroscopy, including NMR shift values of the precursor heterocycles. The X-ray crystal structure determination of bis(Tetraphenylphosphonium)-bis(1,3-thiaselenole-2-selone-4,5-diselenolato) zincate ( 18 ), obtained from 5 , shows the rearrangement of 5 to the 1,3-thiaselenole-2-selone partial structure in 18 .
D B Zorov - One of the best experts on this subject based on the ideXlab platform.
-
neuroprotective effects of mitochondria targeted plastoquinone and thymoquinone in a rat model of brain ischemia reperfusion injury
Molecules, 2015Co-Authors: D N Silachev, Egor Y Plotnikov, Ljubava D Zorova, I B Pevzner, N V Sumbatyan, G A Korshunova, M V Gulyaev, Y A Pirogov, V P Skulachev, D B ZorovAbstract:We explored the neuroprotective properties of natural plant-derived antioxidants plastoquinone and thymoquinone (2-demethylplastoquinone derivative) modified to be specifically accumulated in mitochondria. The modification was performed through chemical conjugation of the quinones with penetrating cations: Rhodamine 19 or Tetraphenylphosphonium. Neuroprotective properties were evaluated in a model of middle cerebral artery occlusion. We demonstrate that the mitochondria-targeted compounds, introduced immediately after reperfusion, possess various neuroprotective potencies as judged by the lower brain damage and higher neurological status. Plastoquinone derivatives conjugated with rhodamine were the most efficient, and the least efficiency was shown by antioxidants conjugated with Tetraphenylphosphonium. Antioxidants were administered intraperitoneally or intranasally with the latter demonstrating a high level of penetration into the brain tissue. The therapeutic effects of both ways of administration were similar. Long-term administration of antioxidants in low doses reduced the neurological deficit, but had no effect on the volume of brain damage. At present, cationic decylrhodamine derivatives of plastoquinone appear to be the most promising anti-ischemic mitochondria-targeted drugs of the quinone family. We suggest these antioxidants could be potentially used for a stroke treatment.
-
Neuroprotective Effects of Mitochondria-Targeted Plastoquinone and Thymoquinone in a Rat Model of Brain Ischemia/Reperfusion Injury
MDPI AG, 2015Co-Authors: D N Silachev, Egor Y Plotnikov, Ljubava D Zorova, I B Pevzner, N V Sumbatyan, G A Korshunova, M V Gulyaev, Y A Pirogov, V P Skulachev, D B ZorovAbstract:We explored the neuroprotective properties of natural plant-derived antioxidants plastoquinone and thymoquinone (2-demethylplastoquinone derivative) modified to be specifically accumulated in mitochondria. The modification was performed through chemical conjugation of the quinones with penetrating cations: Rhodamine 19 or Tetraphenylphosphonium. Neuroprotective properties were evaluated in a model of middle cerebral artery occlusion. We demonstrate that the mitochondria-targeted compounds, introduced immediately after reperfusion, possess various neuroprotective potencies as judged by the lower brain damage and higher neurological status. Plastoquinone derivatives conjugated with rhodamine were the most efficient, and the least efficiency was shown by antioxidants conjugated with Tetraphenylphosphonium. Antioxidants were administered intraperitoneally or intranasally with the latter demonstrating a high level of penetration into the brain tissue. The therapeutic effects of both ways of administration were similar. Long-term administration of antioxidants in low doses reduced the neurological deficit, but had no effect on the volume of brain damage. At present, cationic decylrhodamine derivatives of plastoquinone appear to be the most promising anti-ischemic mitochondria-targeted drugs of the quinone family. We suggest these antioxidants could be potentially used for a stroke treatment
