RESUMO
In order to model the individual electron transfer steps from the manganese cluster to the photooxidized sensitizer P680+ in Photosystem II (PS II) in green plants, the supramolecular complex 4 has been synthesized. In this complex, a ruthenium(II) tris-bipyridine type photosensitizer has been linked to a manganese(II) dimer via a substituted L-tyrosine, which bridges the manganese ions. The trinuclear complex 4 was characterized by electron paramagnetic resonance (EPR) and electrospray ionization mass spectrometry (ESI-MS). The excited state lifetime of the ruthenium tris-bipyridine moiety in 4 was found to be about 110 ns in acetonitrile. Using flash photolysis in the presence of an electron acceptor (methylviologen), it was demonstrated that in the supramolecular complex 4 an electron was transferred from the excited state of the ruthenium tris-bipyridine moiety to methylviologen, forming a methylviologen radical and a ruthenium(III) tris-bipyridine moiety. Next, the Ru(III) species retrieved the electron from the manganese(II/II) dimer in an intramolecular electron transfer reaction with a rate constant kET > 1.0 x 10(7) s(-1), generating a manganese(II/III) oxidation state and regenerating the ruthenium(II) photosensitizer. This is the first example of intramolecular electron transfer in a supramolecular complex, in which a manganese dimer is covalently linked to a photosensitizer via a tyrosine unit, in a process which mimics the electron transfer on the donor side of PS II.
Assuntos
Complexo de Proteínas do Centro de Reação Fotossintética/química , 2,2'-Dipiridil/análogos & derivados , 2,2'-Dipiridil/síntese química , 2,2'-Dipiridil/química , 2,2'-Dipiridil/metabolismo , Complexos de Coordenação , Dimerização , Espectroscopia de Ressonância de Spin Eletrônica , Elétrons , Cromatografia Gasosa-Espectrometria de Massas , Ligação de Hidrogênio , Indicadores e Reagentes/química , Manganês/química , Manganês/metabolismo , Modelos Moleculares , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Compostos Organometálicos/síntese química , Compostos Organometálicos/química , Compostos Organometálicos/metabolismo , Fotólise , Complexo de Proteína do Fotossistema II , Espectrometria de Massas de Bombardeamento Rápido de Átomos , Tirosina/síntese química , Tirosina/química , Tirosina/metabolismoRESUMO
A 27 year old, HIV positive, homosexual man was admitted for evaluation and treatment of acute oligoarticular arthritis. Gonococcal arthritis was found in a single hip and a single sternoclavicular joint, which is an unusual distribution for this bacterial pathogen.