Linked Life Data

9778366

Source:http://linkedlifedata.com/resource/pubmed/id/9778366

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
42
pubmed:dateCreated
1998-11-18
pubmed:abstractText
The triplet states of antenna and reaction center bacteriochlorophyll (BChl) g in membranes of Heliobacterium chlorum were studied by optically detected magnetic resonance in zero magnetic field, using absorbance detection. A variety of triplet states was detected, which were all localized on single BChl g chromophores as concluded from a comparison with the triplet state of monomeric BChl g in organic solvents. With the aid of the microwave-induced absorbance difference spectra, we assign a triplet state with zero-field splitting parameters |D| = 727.5 and |E| = 254. 5 MHz to that of the primary donor. The low |E| value indicates that the BChls of the primary donor are monoligated. The intensities of the zero-field transitions were strongly dependent on the redox state of the secondary electron acceptors. A triplet state with |D| = 690-705 MHz and |E| =230 MHz, present under all redox conditions, is associated with antenna BChl g absorbing at 814 nm. Its triplet yield was independent of the redox conditions; we conclude therefore that the antenna chromophores absorbing at 814 nm are not connected with the reaction center at cryogenic temperatures (1.2 K). In addition, relatively strong signals were detected belonging to triplet states with |D| and |E| of 663-680 and 220-227 MHz, respectively, whose amplitudes were dependent on the redox conditions. Triplet states with these zero-field splitting parameters are located on antenna chromophores absorbing between 798-814 nm; their zero-field transitions and absorbance difference spectra indicate a considerable heterogeneity. The concentration of triplet states of antenna chromophores absorbing around 800 nm decreased markedly upon prolonged excitation at 1.2 K. This phenomenon is attributed to quenching of excitations on antenna pigments by stable charge separation in the closely connected reaction center, possibly involving a low-quantum yield menaquinone electron acceptor.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
20
pubmed:volume
37
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
14900-9
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Triplet properties and interactions of the primary electron donor and antenna chromophores in membranes of Heliobacterium chlorum, studied with ADMR spectroscopy.
pubmed:affiliation
Department of Biophysics, Huygens Laboratory, Leiden University, The Netherlands.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't