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Tuning proton coupl...
Tuning proton coupled electron transfer from tyrosine : A competition between concerted and step-wise mechanisms
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Sjodin, M. (författare)
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- Ghanem, Raed (författare)
- Lund University,Lunds universitet,Kemisk fysik,Enheten för fysikalisk och teoretisk kemi,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Chemical Physics,Physical and theoretical chemistry,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH
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- Polivka, Tomas (författare)
- Lund University,Lunds universitet,Kemisk fysik,Enheten för fysikalisk och teoretisk kemi,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Chemical Physics,Physical and theoretical chemistry,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH
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- Pan, Jie (författare)
- Lund University,Lunds universitet,Kemisk fysik,Enheten för fysikalisk och teoretisk kemi,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Chemical Physics,Physical and theoretical chemistry,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH
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- Styring, Stenbjörn (författare)
- Lund University,Lunds universitet,Biokemi och Strukturbiologi,Centrum för Molekylär Proteinvetenskap,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Biochemistry and Structural Biology,Center for Molecular Protein Science,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH
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Sun, Licheng C. (författare)
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- Sundström, Villy (författare)
- Lund University,Lunds universitet,Kemisk fysik,Enheten för fysikalisk och teoretisk kemi,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Chemical Physics,Physical and theoretical chemistry,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH
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Hammarstrom, L. (författare)
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(creator_code:org_t)
- 2004
- 2004
- Engelska.
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 6:20, s. 4851-4858
- Relaterad länk:
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http://dx.doi.org/10...
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https://urn.kb.se/re...
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https://doi.org/10.1...
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https://lup.lub.lu.s...
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Abstract
Ämnesord
Stäng
- The intra-molecular, proton-coupled electron transfer from a tyrosine residue to covalently linked tris-bipyridine ruthenium(III) complexes in aqueous solution (Ru-III-TyrOH --> Ru-II-TyrO(.) + H+) is studied in two complexes. The Ru-III-TyrOH state is generated by laser flash-induced photo-oxidation in the presence of the electron acceptor methyl viologen. The reaction is shown to follow either a concerted electron transfer-deprotonation (CEP) mechanism or a step-wise mechanism with electron transfer followed by deprotonation (ETPT). The CEP is characterised by a pH-dependent rate constant, a large reorganisation energy (lambda = 1.4 eV at pH = 7) and a significant kinetic isotope effect: k(H)/k(D) = 1.5-3. We can explain the pH-dependence and the high lambda by the pH-dependent DeltaGdegrees' for proton release to bulk water, and by the additional reorganisation energy associated with the proton transfer coordinate (both internal and solvent), respectively. In the calculation of lambda from the temperature dependent rate constant, correction is made for the large entropy increase of the reaction (TDeltaS(rxn) approximate to0.41 eV at pH = 7 and T = 298 K). The step-wise ETPT mechanism on the other hand shows a pH-independent rate, a lower reorganisation energy and no kinetic isotope effect. We propose that our complexes can be used as models to understand proton-coupled electron transfer in radical proteins. We show that the mechanism can be switched between CEP and ETPT by tuning the reaction pH and the electrochemical potential of the Ru-III/II oxidant. With a low driving force for the overall reaction the energy conservative CEP mechanism may dominate, in spite of the higher reorganisation energy as compared to ETPT.
Ämnesord
- NATURVETENSKAP -- Fysik -- Atom- och molekylfysik och optik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Atom and Molecular Physics and Optics (hsv//eng)
- NATURVETENSKAP -- Biologi (hsv//swe)
- NATURAL SCIENCES -- Biological Sciences (hsv//eng)
Nyckelord
- photosystem-ii
- water oxidation
- redox potentials
- complex
- oxygen
- chemistry
- phenols
Publikations- och innehållstyp
- ref (ämneskategori)
- art (ämneskategori)
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