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RESEARCH PRODUCT

Thermally Activated Superradiance and Intersystem Crossing in the Water-Soluble Chlorophyll Binding Protein

Harald PaulsenAndreas KnorrThomas RengerFranz-josef SchmittH. J. EichlerG. RengerMohamed MadjetFrank MühI. TrostmannC. Theiss

subject

Models MolecularCircular DichroismDimerExcitonStatic ElectricityLight-Harvesting Protein ComplexesTemperatureWaterCrystal structureCrystallography X-RayPhotochemistryLepidiumSurfaces Coatings and Filmschemistry.chemical_compoundCrystallographyIntersystem crossingSolubilitychemistryChlorophyllExcited stateMaterials ChemistryChlorophyll bindingQuantum TheoryPhysical and Theoretical ChemistryAbsorption (chemistry)

description

The crystal structure of the class IIb water-soluble chlorophyll binding protein (WSCP) from Lepidium virginicum is used to model linear absorption and circular dichroism spectra as well as excited state decay times of class IIa WSCP from cauliflower reconstituted with chlorophyll (Chl) a and Chl b. The close agreement between theory and experiment suggests that both types of WSCP share a common Chl binding motif, where the opening angle between pigment planes in class IIa WSCP should not differ by more than 10 degrees from that in class IIb. The experimentally observed (Schmitt et al. J. Phys. Chem. B 2008, 112, 13951) decrease in excited state lifetime of Chl a homodimers with increasing temperature is fully explained by thermally activated superradiance via the upper exciton state of the dimer. Whereas a temperature-independent intersystem crossing (ISC) rate is inferred for WSCP containing Chl a homodimers, that of WSCP with Chl b homodimers is found to increase above 100 K. Our quantum chemical/electrostatic calculations suggest that a thermally activated ISC via an excited triplet state T4 is responsible for the latter temperature dependence.

yearjournalcountryeditionlanguage
2009-06-25The Journal of Physical Chemistry B
https://doi.org/10.1021/jp901886w