Browsing by Subject "Oxidation-Reduction"

Article

Aerial Oxidation of a VIV-Iminopyridine Hydroquinonate Complex: A Trap for the VIV-Semiquinonate Radical Intermediate

Stylianou, M.; Drouza, C.; Giapintzakis, John; Athanasopoulos, G. I.; Keramidas, A. D. (2015)

The reaction of 2,5-bis[N,N′-bis(2-pyridyl-aminomethyl)aminomethyl]-p-hydroquinone (H2bpymah) with VO2+ salts in acetonitrile or water at a low pH (2.2-3.5) results in the isolation of [VIV(O)(Cl)2(μ-bpymah)], the ...

Article

Aerial Oxidation of a VIV-Iminopyridine Hydroquinonate Complex: A Trap for the VIV-Semiquinonate Radical Intermediate

Stylianou, Marios; Drouza, Chryssoula; Giapintzakis, Ioannis; Athanasopoulos, Georgios I.; Keramidas, Anastasios D. (2015)

The reaction of 2,5-bis[N,N′-bis(2-pyridyl-aminomethyl)aminomethyl]-p-hydroquinone (H2bpymah) with VO2+ salts in acetonitrile or water at a low pH (2.2-3.5) results in the isolation of [{VIV(O)(Cl)}2(μ-bpymah)], the ...

Article

Biological charge transfer via flickering resonance

Zhang, Y.; Liu, C.; Balaeff, A.; Skourtis, Spiros S.; Beratan, David N. (2014)

Biological electron-transfer (ET) reactions are typically described in the framework of coherent two-state electron tunneling or multistep hopping. However, these ET reactions may involve multiple redox cofactors in van ...

Article

Detection of the His-heme Fe2+-NO species in the reduction of NO to N2O by ba3-oxidase from thermus thermophilus

Pinakoulaki, Eftychia; Ohta, T.; Soulimane, T.; Kitagawa, T.; Varotsis, Constantinos (2005)

Reaction pathways in the enzymatic formation and cleavage of the N-N and N-O bonds, respectively, are difficult to verify without the structure of the intermediates, but we now have such information on the heme a3 2+-NO ...

Article

Direct detection of Fe(IV)=O intermediates in the cytochrome aa3 oxidase from Paracoccus denitrificans[H2O2 reaction

Pinakoulaki, Eftychia; Pfitzner, U.; Ludwig, B.; Varotsis, Constantinos (2003)

We report the first evidence for the formation of the "607- and 580-nm forms" in the cytochrome oxidase aa3/H2O2 reaction without the involvement of tyrosine 280. The pKa of the 607-580-nm transition is 7.5. The 607-nm ...

Article

Donor atom electrochemical contribution to redox potentials of square pyramidal vanadyl complexes

Vlasiou, Manolis; Drouza, Chryssoula; Kabanos, Themistoklis A.; Keramidas, Anastasios D. (2015)

A simple donor atom additivity relationship has been used to calculate the donor atom electrochemical contribution (DEC) of the Oac (acetylacetonate-enolic oxygen), OPh (phenolic oxygen), SPh (mercaptophenol sulfur), Nam ...

Article

High nuclearity single-molecule magnets: A mixed-valence Mn26 cluster containing the di-2-pyridylketone diolate dianion

Stamatatos, Theocharis C.; Nastopoulos, Vassilios; Tasiopoulos, Anastasios J.; Moushi, Eleni E.; Wernsdorfer, W.; Christou, George; Perlepes, Spyros P. (2008)

The employment of the dianion (dpkd2-) of the gem-diol form of di-2-pyridylketone (dpk) as a tetradentate chelate in manganese chemistry is reported, and the synthesis, crystal structure, and magnetochemical characterization ...

Article

Is vanadate reduced by thiols under biological conditions? Changing the Redox potential of V(V)/V(IV) by complexation in aqueous solution

Crans, D. C.; Zhang, B.; Gaidamauskas, E.; Keramidas, Anastasios D.; Willsky, G. R.; Roberts, C. R. (2010)

Although dogma states that vanadate is readily reduced by glutathione, cysteine, and other thiols, there are several examples documenting that vanadium(V)-sulfur complexes can form and be observed. This conundrum has ...

Article

Mixed transition metal-lanthanide complexes at high oxidation states: Heteronuclear CeIVMnIV clusters

Tasiopoulos, Anastasios J.; Milligan Jr., P. L.; Abboud, K. A.; O'Brien, T. A.; Christou, George (2007)

The syntheses of the first mixed-metal CeIVMnIV complexes are reported. [CeMn2O3(O2CMe)(NO 3)4(H2O)2(bpy)2]-(NO 3) (1

Article

Nickel/lanthanide single-molecule magnets: {Ni3Ln} "stars" with a ligand derived from the metal-promoted reduction of di-2-pyridyl ketone under solvothermal conditions

Efthymiou, Constantinos G.; Stamatatos, Theocharis C.; Papatriantafyllopoulou, Constantina; Tasiopoulos, Anastasios J.; Wernsdorfer, W.; Perlepes, Spyros P.; Christou, George (2010)

Unusual {NiII3LnIII(μ-OR) 6}3+ complexes with a "star" topology have been prepared with ligands derived from the metal-promoted reduction of di-2-pyridyl ketone under solvothermal conditions

Article

Nitric oxide activation and reduction by heme-copper oxidoreductases and nitric oxide reductase

Pinakoulaki, Eftychia; Varotsis, Constantinos (2008)

The understanding of the dynamics and conformational control involved in the interplay between structure and function of nitric oxide reductase (Nor) and heme-copper oxidoreductases in their function to convert nitric oxide ...

Article

Nitric-oxide reductase: Structure and properties of the catalytic site from resonance Raman scattering

Pinakoulaki, Eftychia; Gemeinhardt, S.; Saraste, M.; Varotsis, Constantinos (2002)

We have applied resonance Raman spectroscopy to investigate the properties of the dinuclear center of oxidized, reduced, and NO-bound nitric-oxide reductase from Paracoccus denitrificans. The spectra of the oxidized enzyme ...

Article

Novel approach to fast determination of cholesterol oxidation products in Cypriot foodstuffs using ultra-performance liquid chromatography-tandem mass spectrometry

Georgiou, Christiana A.; Constantinou, Michalis S.; Andreou, Rafaella; Hapeshi, Evroula; Fatta‐Kassinos, Despo; Kapnissi‐Christodoulou, Constantina P. (2016)

This paper reports the development and validation of a new method based on ultra-performance LC coupled to MS/MS for the simultaneous determination of four cholesterol oxidation products (COPs) in foodstuffs in only 4.1 ...

Article

Novel approach to fast determination of cholesterol oxidation products in Cypriot foodstuffs using ultra-performance liquid chromatography-tandem mass spectrometry

Georgiou, Christiana A.; Constantinou, Michalis S.; Andreou, Rafaella; Hapeshi, E.; Fatta-Kassinos, Despo; Kapnissi-Christodoulou, Constantina (2016)

This paper reports the development and validation of a new method based on ultra-performance LC coupled to MS/MS for the simultaneous determination of four cholesterol oxidation products (COPs) in foodstuffs in only 4.1 ...

Article

Novel lipophilic amidate oxorhenium and oxotechnetium complexes as potential brain agents: Synthesis, characterization and biological evaluation

Papadopoulos, Minas S.; Nock, B.; Maina-Nock, Theodosia; Pirmettis, Ioannis C.; Raptopoulou, Catherine P.; Tasiopoulos, Anastasios J.; Troganis, Anastassios N.; Kabanos, Themistoklis A.; Terzis, Aris; Chiotellis, Efstratios (2001)

Novel oxorhenium and oxotechnetium complexes based on the tetradentate 1-(2-hydroxybenzamido)-2-(pyridinecarboxamido)benzene, H3L, ligand have been synthesized and characterized herein. Thus, by reacting equimolar quantities ...

Article

The origin of the Fe IV = O intermediates in cytochrome aa 3 oxidase

Pinakoulaki, Eftychia; Daskalakis, Vangelis; Varotsis, Constantinos (2012)

The dioxygen reduction mechanism in cytochrome oxidases relies on proton control of the electron transfer events that drive the process. Proton delivery and proton channels in the protein that are relevant to substrate ...

Article

Oxidovanadium(IV/V) complexes as new redox mediators in dye-sensitized solar cells: A combined experimental and theoretical study

Apostolopoulou, Andigoni; Vlasiou, Manolis; Tziouris, Petros A.; Tsiafoulis, Constantinos G.; Tsipis, Athanassios C.; Rehder, D.; Kabanos, Themistoklis A.; Keramidas, Anastasios D.; Stathatos, Elias (2015)

Corrosiveness is one of the main drawbacks of using the iodide/triiodide redox couple in dye-sensitized solar cells (DSSCs). Alternative redox couples including transition metal complexes have been investigated where ...

Article

Physical constraints on charge transport through bacterial nanowires

Polizzi, N. F.; Skourtis, Spiros S.; Beratan, David N. (2012)

Extracellular appendages of the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 were recently shown to sustain currents of 10 10 electrons per second over distances of 0.5 microns [El-Naggar et al., Proc. ...

Article

Probing the nitrite and nitric oxide reductase activity of cbb3 oxidase: Resonance Raman detection of a six-coordinate ferrous heme-nitrosyl species in the binuclear b3/CuB center

Loullis, Andreas; Pinakoulaki, Eftychia (2015)

In this work we report the first spectroscopic evidence demonstrating that cbb3 oxidase catalyzes the reduction of nitrite to nitrous oxide under reducing anaerobic conditions. The reaction proceeds through the formation ...

Article

The protein effect in the structure of two ferryl-oxo intermediates at the same oxidation level in the heme copper binuclear center of cytochrome c oxidase

Pinakoulaki, Eftychia; Daskalakis, Vangelis; Ohta, T.; Richter, O. -M H.; Budiman, K.; Kitagawa, T.; Ludwig, B.; Varotsis, Constantinos (2013)

Identification of the intermediates and determination of their structures in the reduction of dioxygen to water by cytochrome c oxidase (CcO) are particularly important to understanding both O2 activation and proton pumping ...