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Article: A Possible Role for Singlet Oxygen in the Degradation of Various Antioxidants. A Meta-Analysis and Review of Literature Data.

Petrou, Athinoula L / Petrou, Petros L / Ntanos, Theodoros / Liapis, Antonis

2018 Volume 7, Issue 3

Abstract: The thermodynamic parameters ... ...

Abstract	The thermodynamic parameters E
Language	English
Publishing date	2018-02-27
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2704216-9
ISSN	2076-3921
ISSN	2076-3921
DOI	10.3390/antiox7030035
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: A meta-analysis and review examining a possible role for oxidative stress and singlet oxygen in diverse diseases.

Petrou, Athinoula L / Terzidaki, Athina

The Biochemical journal

2017 Volume 474, Issue 16, Page(s) 2713–2731

Abstract: From kinetic data (k, T) we calculated the thermodynamic parameters for various processes (nucleation, elongation, fibrillization, etc.) of proteinaceous diseases that are related to the β-amyloid protein (Alzheimer's), to tau protein (Alzheimer's, Pick' ... ...

Abstract	From kinetic data (k, T) we calculated the thermodynamic parameters for various processes (nucleation, elongation, fibrillization, etc.) of proteinaceous diseases that are related to the β-amyloid protein (Alzheimer's), to tau protein (Alzheimer's, Pick's), to α-synuclein (Parkinson's), prion, amylin (type II diabetes), and to α-crystallin (cataract). Our calculations led to ΔG
MeSH term(s)	Alzheimer Disease/metabolism ; Alzheimer Disease/pathology ; Amyloid beta-Peptides/chemistry ; Amyloid beta-Peptides/metabolism ; Cataract/metabolism ; Cataract/pathology ; Diabetes Mellitus, Type 2/metabolism ; Diabetes Mellitus, Type 2/pathology ; Energy Metabolism ; Humans ; Islet Amyloid Polypeptide/chemistry ; Islet Amyloid Polypeptide/metabolism ; Oxidative Stress ; Oxygen/chemistry ; Oxygen/metabolism ; Parkinson Disease/metabolism ; Parkinson Disease/pathology ; Singlet Oxygen ; Thermodynamics ; alpha-Crystallins/chemistry ; alpha-Crystallins/metabolism ; alpha-Synuclein/chemistry ; alpha-Synuclein/metabolism ; tau Proteins/chemistry ; tau Proteins/metabolism
Chemical Substances	Amyloid beta-Peptides ; Islet Amyloid Polypeptide ; alpha-Crystallins ; alpha-Synuclein ; tau Proteins ; Singlet Oxygen (17778-80-2) ; Oxygen (S88TT14065)
Language	English
Publishing date	2017-08-02
Publishing country	England
Document type	Journal Article ; Meta-Analysis ; Review
ZDB-ID	2969-5
ISSN	1470-8728 ; 0006-2936 ; 0306-3275 ; 0264-6021
ISSN (online)	1470-8728
ISSN	0006-2936 ; 0306-3275 ; 0264-6021
DOI	10.1042/BCJ20161058
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Article: The Free Energy of Activation as the critical factor in geochemical processes

Petrou, Athinoula L

Chemical geology. 2012 May 20, v. 308-309

2012

Abstract: By studying the Free Energy of Activation, ΔG≠, of various geochemical transformations we have revealed the importance of the contribution of the entropy of activation, ΔS≠, in the energetics of the processes. In studies performed so far including ... ...

Abstract	By studying the Free Energy of Activation, ΔG≠, of various geochemical transformations we have revealed the importance of the contribution of the entropy of activation, ΔS≠, in the energetics of the processes. In studies performed so far including changes of phases, adsorption, desorption, formation or breaking of bonds, ordering of ions, etc. only the activation energy was considered as the main factor determining the rate of the transformation process through the Arrhenius equation. The above changes result in change of degrees of freedom of the systems. If the above changes happen during the “reactants to transition state or activated complex” step, they result in changes of the entropy of activation. Through the use of the Eyring–Polanyi equation and literature data we were able to determine ΔG≠=ΔH≠−TΔS≠ where ΔH≠ is related to Eₐcₜ=RT+ΔΗ≠ and ΔS≠ is related to A of the Arrhenius equation. It was found that the combination of enthalpy and entropy of activation in ΔG≠ gives a more realistic/true value of the energy requirements of the activation step that the processes need in order to take place. Also, an explanation is given of why calculated activation energy values (that are related only to enthalpy of activation values) for certain transformations deviate from the expected and observed energy requirements that characterize the processes when the entropic component is substantial. This analysis shows that similar processes have similar ΔG≠ values and therefore there is a way of foreseeing the ΔG≠ of a process, if a number of similar processes have been studied and their ΔG≠ values have been calculated.
Keywords	activation energy ; adsorption ; desorption ; energy requirements ; enthalpy ; entropy ; equations ; ions
Language	English
Dates of publication	2012-0520
Size	p. 50-59.
Publishing place	Elsevier B.V.
Document type	Article
ZDB-ID	2179-9
ISSN	0009-2541
ISSN	0009-2541
DOI	10.1016/j.chemgeo.2012.03.015
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Kinetics and Mechanisms of the Chromium(III) Reactions with 2,4- and 2,5-Dihydroxybenzoic Acids in Weak Acidic Aqueous Solutions

Kimon Zavitsanos / Athinoula L. Petrou

Bioinorganic Chemistry and Applications, Vol

2010 Volume 2010

Abstract: The reactions of 2,4- and 2,5-dihydroxybenzoic acids (dihydroxybenzoic acid, DHBA) with chromium(III) in weak acidic aqueous solutions have been shown to take place in at least two stages. The first stage of the reactions has an observed rate constant k1( ...

Abstract	The reactions of 2,4- and 2,5-dihydroxybenzoic acids (dihydroxybenzoic acid, DHBA) with chromium(III) in weak acidic aqueous solutions have been shown to take place in at least two stages. The first stage of the reactions has an observed rate constant k1(obs)=k1[DHBA]+C and the corresponding activation parameters are ΔH1(2,4)≠=49,5 kJ/mol−1, ΔS1(2,4)≠=−103,7 J mol−1 K−1, ΔH1(2,5)≠=60,3 kJ/mol−1, and ΔS1(2,5)≠=−68,0 J mol−1 K−1. These are composite activation parameters and the breaking of the strong intramolecular hydrogen bonding in the two ligands is suggested to be the first step of the (composite) first stage of the reactions. The second stage is ligand concentration independent and is thus attributed to a chelation process. The corresponding activation parameters are ΔH2(2,4)≠=45,13 kJ/mol−1, ΔS2(2,4)≠=−185,9 J mol−1 K−1, ΔH2(2,5)≠=54,55 kJ/mol−1, and ΔS2(2,5)≠=−154,8 J mol−1 K−1. The activation parameters support an associative mechanism for the second stage of the reactions. The various substitution processes are accompanied by proton release, resulting in pH decrease.
Keywords	Biotechnology ; TP248.13-248.65 ; Inorganic chemistry ; QD146-197
Subject code	540
Language	English
Publishing date	2010-01-01T00:00:00Z
Publisher	Hindawi Limited
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Kinetics and Mechanisms of the Chromium(III) Reactions with 2,4- and 2,5-Dihydroxybenzoic Acids in Weak Acidic Aqueous Solutions.

Zavitsanos, Kimon / Petrou, Athinoula L

Bioinorganic chemistry and applications

2010 Volume 2010

Abstract	The reactions of 2,4- and 2,5-dihydroxybenzoic acids (dihydroxybenzoic acid, DHBA) with chromium(III) in weak acidic aqueous solutions have been shown to take place in at least two stages. The first stage of the reactions has an observed rate constant k(1(obs)) = k(1)[DHBA] + C and the corresponding activation parameters are DeltaH(1(2,4)) ( not equal) = 49, 5 kJ/mol(-1), DeltaS(1(2,4)) ( not equal) = -103, 7 J mol(-1) K(-1), DeltaH(1(2,5)) ( not equal) = 60, 3 kJ/mol(-1), and DeltaS(1(2,5)) ( not equal) = -68, 0 J mol(-1) K(-1). These are composite activation parameters and the breaking of the strong intramolecular hydrogen bonding in the two ligands is suggested to be the first step of the (composite) first stage of the reactions. The second stage is ligand concentration independent and is thus attributed to a chelation process. The corresponding activation parameters are DeltaH(2(2,4)) ( not equal) = 45, 13 kJ/mol(-1), DeltaS(2(2,4)) ( not equal) = -185, 9 J mol(-1) K(-1), DeltaH(2(2,5)) ( not equal) = 54, 55 kJ/mol(-1), and DeltaS(2(2,5)) ( not equal) = -154, 8 J mol(-1) K(-1). The activation parameters support an associative mechanism for the second stage of the reactions. The various substitution processes are accompanied by proton release, resulting in pH decrease.
Language	English
Publishing date	2010-07-11
Publishing country	Egypt
Document type	Journal Article
ZDB-ID	2213020-2
ISSN	1687-479X ; 1565-3633
ISSN (online)	1687-479X
ISSN	1565-3633
DOI	10.1155/2010/832768
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Article ; Online: Mechanism of proton transfer to coordinated thiolates: encapsulation of acid stabilizes precursor intermediate.

Alwaaly, Ahmed / Clegg, William / Harrington, Ross W / Petrou, Athinoula L / Henderson, Richard A

Dalton transactions (Cambridge, England : 2003)

2015 Volume 44, Issue 26, Page(s) 11977–11983

Abstract: Earlier kinetic studies on the protonation of the coordinated thiolate in the square-planar [Ni(SC6H4R'-4)(triphos)](+) (R' = NO2, Cl, H, Me or MeO) by lutH(+) (lut = 2,6-dimethylpyridine) indicate a two-step mechanism involving initial formation of a ( ... ...

Abstract	Earlier kinetic studies on the protonation of the coordinated thiolate in the square-planar [Ni(SC6H4R'-4)(triphos)](+) (R' = NO2, Cl, H, Me or MeO) by lutH(+) (lut = 2,6-dimethylpyridine) indicate a two-step mechanism involving initial formation of a (kinetically detectable) precursor intermediate, {[Ni(SC6H4R'-4)(triphos)]···Hlut}(2+) (K(R)1), followed by an intramolecular proton transfer step (k(R)2). The analogous [Ni(SR)(triphos)]BPh4 {R = Et, Bu(t) or Cy; triphos = PhP(CH2CH2PPh2)2} have been prepared and characterized by spectroscopy and X-ray crystallography. Similar to the aryl thiolate complexes, [Ni(SR)(triphos)](+) are protonated by lutH(+) in an equilibrium reaction but the observed rate law is simpler. Analysis of the kinetic data for both [Ni(SR)(triphos)](+) and [Ni(SC6H4R'-4)(triphos)](+) shows that both react by the same mechanism, but that K(R)1 is largest when the thiolate is poorly basic, or the 4-R' substituent in the aryl thiolates is electron-withdrawing. These results indicate that it is both NH···S hydrogen bonding and encapsulation of the bound lutH(+) (by the phenyl groups on triphos) which stabilize the precursor intermediate.
Language	English
Publishing date	2015-07-14
Publishing country	England
Document type	Journal Article
ZDB-ID	1472887-4
ISSN	1477-9234 ; 1364-5447 ; 0300-9246 ; 1477-9226
ISSN (online)	1477-9234 ; 1364-5447
ISSN	0300-9246 ; 1477-9226
DOI	10.1039/c5dt01716e
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Article ; Online: Kinetics and Mechanism of the Reaction between Chromium(III) and 2,3-Dihydroxybenzoic Acid in Weak Acidic Aqueous Solutions.

Petrou, Athinoula L / Thoma, Vladimiros / Tampouris, Konstantinos

Bioinorganic chemistry and applications

2010 , Page(s) 348692

Abstract: The reaction between chromium(III) and 2,3-dihydroxybenzoic acid (2,3-DHBA) takes place in at least three stages, involving various intermediates. The ligand (2,3-DHBA)-to-chromium(III) ratio in the final product of the reaction is 1 : 1. The first stage ...

Abstract	The reaction between chromium(III) and 2,3-dihydroxybenzoic acid (2,3-DHBA) takes place in at least three stages, involving various intermediates. The ligand (2,3-DHBA)-to-chromium(III) ratio in the final product of the reaction is 1 : 1. The first stage is suggested to be the reaction of [Cr(H(2)O)(5)(OH)](2+) with the ligand in weak acidic aqueous solutions that follows an I(d) mechanism. The second and third stages do not depend on the concentrations of chromium(III), and their activation parameters are DeltaH( not equal) (2(obs)) = 61.2 +/- 3.1 kJmol(-1), DeltaS( not equal) (2(obs)) = -91.1 +/- 11.0 JK(-1)mol(-1), DeltaH( not equal) (3(obs)) = 124.5 +/- 8.7 kJmol(-1), and DeltaS( not equal) (3(obs)) = 95.1 +/- 29.0 JK(-1)mol(-1). These two stages are proposed to proceed via associative mechanisms. The positive value of DeltaS( not equal) (3(obs)) can be explained by the opening of a four-membered ring (positive entropy change) and the breaking of a hydrogen bond (positive entropy change) at the associative step of the replacement of the carboxyl group by the hydroxyl group at the chromium(III) center (negative entropy change in associative mechanisms). The reactions are accompanied by proton release, as shown by the pH decrease.
Language	English
Publishing date	2010-05-31
Publishing country	Egypt
Document type	Journal Article
ZDB-ID	2213020-2
ISSN	1687-479X ; 1565-3633
ISSN (online)	1687-479X
ISSN	1565-3633
DOI	10.1155/2010/348692
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Article ; Online: Kinetics and Mechanism of the Reaction between Chromium(III) and 2,3-Dihydroxybenzoic Acid in Weak Acidic Aqueous Solutions

Athinoula L. Petrou / Vladimiros Thoma / Konstantinos Tampouris

Bioinorganic Chemistry and Applications, Vol

2010 Volume 2010

Abstract	The reaction between chromium(III) and 2,3-dihydroxybenzoic acid (2,3-DHBA) takes place in at least three stages, involving various intermediates. The ligand (2,3-DHBA)-to-chromium(III) ratio in the final product of the reaction is 1 : 1. The first stage is suggested to be the reaction of [Cr(H2O)5(OH)]2+ with the ligand in weak acidic aqueous solutions that follows an Id mechanism. The second and third stages do not depend on the concentrations of chromium(III), and their activation parameters are ΔH≠=61.2±3.1 kJmol−1, ΔS≠=−91.1±11.0 JK−1mol−1, ΔH≠=124.5±8.7 kJmol−1, and ΔS≠=95.1±29.0 JK−1mol−1. These two stages are proposed to proceed via associative mechanisms. The positive value of ΔS≠ can be explained by the opening of a four-membered ring (positive entropy change) and the breaking of a hydrogen bond (positive entropy change) at the associative step of the replacement of the carboxyl group by the hydroxyl group at the chromium(III) center (negative entropy change in associative mechanisms). The reactions are accompanied by proton release, as shown by the pH decrease.
Keywords	Biotechnology ; TP248.13-248.65 ; Inorganic chemistry ; QD146-197
Subject code	540
Language	English
Publishing date	2010-01-01T00:00:00Z
Publisher	Hindawi Limited
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Reaction of Chromium(III) with 3,4-Dihydroxybenzoic Acid

Kimon Zavitsanos / Konstantinos Tampouris / Athinoula L. Petrou

Bioinorganic Chemistry and Applications, Vol

Kinetics and Mechanism in Weak Acidic Aqueous Solutions

2008 Volume 2008

Keywords	Inorganic chemistry ; QD146-197 ; Chemistry ; QD1-999 ; Science ; Q ; DOAJ:Inorganic Chemistry ; DOAJ:Chemistry
Language	English
Publishing date	2008-01-01T00:00:00Z
Publisher	Hindawi Publishing Corporation
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Kinetics and Mechanism of the Reaction between Chromium(III) and 3,4-Dihydroxy-Phenyl-Propenoic Acid (Caffeic Acid) in Weak Acidic Aqueous Solutions

Vladimiros Thoma / Konstantinos Tampouris / Athinoula L. Petrou

Bioinorganic Chemistry and Applications, Vol

2008 Volume 2008

Keywords	Inorganic chemistry ; QD146-197 ; Chemistry ; QD1-999 ; Science ; Q ; DOAJ:Inorganic Chemistry ; DOAJ:Chemistry
Language	English
Publishing date	2008-01-01T00:00:00Z
Publisher	Hindawi Publishing Corporation
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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