The rate ladder of proton-coupled tyrosine oxidation in water

A systematic dependence on hydrogen bonds and protonation state

Tania Irebo, Olof Johansson, Leif Hammarström

Research output: Contribution to journalArticle

47 Citations (Scopus)

Abstract

Proton coupled electron transfer (PCET) from tyrosine covalently linked to Ru(bpy)3 2+ has been studied with laser flash-quench techniques. Two new complexes with internal hydrogen bonding bases to the phenolic proton have been synthesized. Depending on the hydrogen bonding and protonation situation the rate constant of PCET spanned over 5 orders of magnitude and revealed a systematic dependence on pH. This resulted in a previously predicted "rate ladder" scheme: (i) pH dependent concerted electron-proton transfer (CEP) with deprotonation to bulk water, giving low PCET rates, (ii) pH independent CEP with deprotonation to the internal base, giving intermediate PCET rates, and (iii) pure electron transfer from tyrosinate, giving high rates. This behavior is reminiscent of Yz oxidation in Mn-depleted and native photosystem II. The study also revealed important differences in rates between phenols with strong and weak hydrogen bonds, and for the latter a hydrogen bond-gated PCET was observed.

Original languageEnglish
Pages (from-to)9194-9195
Number of pages2
JournalJournal of the American Chemical Society
Volume130
Issue number29
DOIs
Publication statusPublished - Jul 23 2008

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Protonation
Ladders
Tyrosine
Protons
Hydrogen
Hydrogen bonds
Electrons
Oxidation
Water
Deprotonation
Proton transfer
Hydrogen Bonding
Photosystem II Protein Complex
Phenols
Rate constants
Lasers

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

The rate ladder of proton-coupled tyrosine oxidation in water : A systematic dependence on hydrogen bonds and protonation state. / Irebo, Tania; Johansson, Olof; Hammarström, Leif.

In: Journal of the American Chemical Society, Vol. 130, No. 29, 23.07.2008, p. 9194-9195.

Research output: Contribution to journalArticle

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