Browsing Τμήμα Χημείας / Department of Chemistry by Author "Varotsis, Constantinos"
Now showing items 1-20 of 24
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The Active Site Structure of Heme a3 3+-C≡N-CuB2+ of Cytochrome aa 3 Oxidase as Revealed from Resonance Raman Scattering
Pinakoulaki, Eftychia; Vamvouka, M.; Varotsis, Constantinos (2003)Resonance Raman and FTIR spectroscopies have been employed to investigate the structure of the heme a3-C≡N-CuB complex of oxidized cytochrome aa3 oxidase. The characterization of this complex is essential since a central ...
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Decay of the transient CuB-CO complex is accompanied by formation of the heme Fe-CO complex of cytochrome cbb3-CO at ambient temperature: Evidence from time-resolved fourier transform infrared spectroscopy
Stavrakis, Stavros; Koutsoupakis, Constantinos; Pinakoulaki, Eftychia; Urban, A.; Saraste, M.; Varotsis, Constantinos (2002)Time-resolved step-scan Fourier infrared spectroscopy has been used to study the CO-bound cbb3-type cytochrome c oxidase from Pseudomonas stutzeri at room temperature. We observe a single band in the FTIR spectrum at 1956 ...
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Detection of a photostable five-coordinate heme a3-Fe-Co species and functional implications of His384/α10 in CO-bound ba 3-cytochrome c oxidase from Thermus thermophilus
Ohta, T.; Pinakoulaki, Eftychia; Soulimane, T.; Kitagawa, T.; Varotsis, Constantinos (2004)Resonance Raman (RR) spectra are reported for the fully reduced carbon monoxy derivative of ba3-cytochrome c oxidase from Thermus thermophilus. The RR spectra show the formation of a photolabile six-coordinate heme-CO and ...
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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 ...
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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 ...
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Fourier transform infrared (FTIR) and step-scan time-resolved FTIR spectroscopies reveal a unique active site in cytochrome caa3 oxidase from Thermus thermophilus
Pinakoulaki, Eftychia; Soulimane, T.; Varotsis, Constantinos (2002)Fourier transform infrared (FTIR) and step-scan time-resolved FTIR difference spectra are reported for the [carbonmonoxy]cytochrome caa3 from Thermus thermophilus. A major C-O mode of heme a3 at 1958 cm-1 and two minor ...
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Fourier transform infrared evidence for a ferric six-coordinate nitrosylheme b3 complex of cytochrome cbb3 oxidase from Pseudomonas stutzeri at ambient temperature
Stavrakis, Stavros; Pinakoulaki, Eftychia; Urbani, A.; Varotsis, Constantinos (2002)We report the first vibrational study of NO bound to an oxidized heme-copper oxidase. Cytochrome cbb3 oxidase from P. stutzeri reduces both O2 and NO to H2O and N2O, respectively. The ferric nitrosyl complex of cbb3 exhibits ...
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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 ...
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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 ...
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Observation of the equilibrium CuB-CO complex and functional implications of the transient heme a3 propionates in cytochrome ba3-CO from Thermus thermophilus. Fourier transform infrared (FTIR) and time-resolved step-scan FTIR studies
Koutsoupakis, Constantinos; Stavrakis, Stavros; Pinakoulaki, Eftychia; Soulimane, T.; Varotsis, Constantinos (2002)We report the first evidence for the existence of the equilibrium CuB 1+-CO species of CO-bound reduced cytochrome ba3 from Thermus thermophilus at room temperature. The frequency of the C-O stretching mode of CuB 1+-CO ...
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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 ...
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Probing the environment of CuB in heme-copper oxidases
Daskalakis, Vangelis; Pinakoulaki, Eftychia; Stavrakis, Stavros; Varotsis, Constantinos (2007)Time-resolved step-scan FTIR (TRS2-FTIR) and density functional theory have been applied to probe the structural dynamics of CuB in heme-copper oxidases at room temperature. The TRS2-FTIR data of cbb3 from Pseudomonas ...
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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 ...
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Recognition and discrimination of gases by the oxygen-sensing signal transducer protein HemAT as revealed by FTIR spectroscopy
Pinakoulaki, Eftychia; Yoshimura, H.; Yoshioka, S.; Aono, S.; Varotsis, Constantinos (2006)The determination of ligand binding properties is a key step in our understanding of gas sensing and discrimination by gas sensory proteins. HemAT is a newly discovered signal transducer heme protein that recognizes O 2 ...
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Resonance Raman detection of a ferrous five-coordinate nitrosylheme b3 complex in cytochrome cbb3 oxidase from Pseudomonas stutzeri
Pinakoulaki, Eftychia; Stavrakis, Stavros; Urbani, A.; Varotsis, Constantinos (2002)Understanding the chemical nature of the nitric oxide (NO) moiety of nitrosylheme copper oxidases is crucial for elucidation of the NO activation process. In the present work, direct resonance Raman spectroscopic observation ...
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Resonance Raman detection of the Fe2+-C-N modes in heme-copper oxidases: A probe of the active site
Pinakoulaki, Eftychia; Vamvouka, M.; Varotsis, Constantinos (2004)Resonance Raman spectroscopy has been employed to investigate the reduced cyano complexes of cytochrome aa3 from bovine heart and Rhodobacter sphaeroides and of cytochrome bo3 from E. coli. In the aa 3-type oxidases, the ...
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Resonance raman spectroscopy of nitric oxide reductase and cbb3 Heme-Copper oxidase
Pinakoulaki, Eftychia; Varotsis, Constantinos (2008)Elucidating the structure and properties of the active sites in cbf 3 heme-copper oxidase and in nitric oxide reductase (Nor) is crucial in understanding the reaction mechanisms of oxygen and nitric oxide reduction by both ...
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The role of the cross-link His-Tyr in the functional properties of the binuclear center in cytochrome c oxidase
Pinakoulaki, Eftychia; Pfitzner, U.; Ludwig, B.; Varotsis, Constantinos (2002)Resonance Raman and Fourier transform infrared spectroscopies have been used to study the aa3-type cytochrome c oxidase and the Y280H mutant from Paracoccus denitrificans. The stability of the binuclear center in the absence ...
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Simultaneous resonance Raman detection of the heme a3-Fe-CO and CuB-CO species in CO-bound ba3-cytochrome c oxidase from Thermus thermophilus: Evidence for a charge transfer CuB-CO transition
Pinakoulaki, Eftychia; Ohta, T.; Soulimane, T.; Kitagawa, T.; Varotsis, Constantinos (2004)Understanding of the chemical nature of the dioxygen and nitric oxide moiety of ba3-cytochrome c oxidase from Thermus thermophilus is crucial for elucidation of its physiological function. In the present work, direct ...
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Structural dynamics of heme-copper oxidases and nitric oxide reductases: Time-resolved step-scan Fourier transform infrared and time-resolved resonance Raman studies
Pinakoulaki, Eftychia; Koutsoupakis, Constantinos; Stavrakis, Stavros; Aggelaki, Marialena; Papadopoulos, George Angelos; Daskalakis, Vangelis; Varotsis, Constantinos (2005)Of the spectroscopic methods available for the characterization of the dynamics of heme protein active sites, time-resolved resonance Raman spectroscopy (TR3) is a powerful technique because excitation within the heme π-π* ...