Stark effect in wild-type and heterodimer-containing reaction centers from Rhodobacter capsulatus

Journal Article · Tue Jan 30 00:00:00 EST 1990 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00456a008· OSTI ID:6710021

DiMagno, T J; Norris, J R ^[1]; Bylina, E J; Youvan, D C ^[2]; Angerhofer, A ^[3]

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1. Univ. of Chicago, IL (USA) Argonne National Lab., IL (USA)
2. Massachusetts Institute of Technology, Cambridge (USA)
3. Argonne National Lab., IL (USA)

The effect of an external electric field on the optical absorption spectra of wild-type Rhodobacter capsulatus and two Rb. capsulatus reaction centers that have been genetically modified through site-directed mutagenesis was measured at 77 K. The two genetically modified reaction centers replace histidine M200, the axial ligand to the M-side bacteriochlorophyll of the special pair, with either leucine or phenylalanine. These substitutions results in the replacement of the M-side bacteriochlorophyll with bacteriopheophytin, forming a bacteriochlorophyll-bacteriopheophytin heterodimer. The magnitude of the change in dipole moment from the ground to excited state ({Delta}{mu}{sub app}) and the angle {delta} between the Q{sub y} transition moment and the direction of {Delta}{mu}{sub app} were measured for the special pair absorption band for all three reaction centers. The differences in the magnitude of {Delta}{mu}{sub app} and the angle {delta} between wild-type and heterodimer reaction centers are consistent with increased charge transfer in the heterodimer special pair. These results support calculations that place the special pair charge-transfer state higher in energy than the excited singlet state in wild-type Rb. capsulatus RCs.

• DOE Contract Number: W-31-109-ENG-38
• OSTI ID: 6710021
• Journal Information: Biochemistry; (USA), Vol. 29:4; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CHLOROPHYLL
DIPOLE MOMENTS
PHOTOSYNTHETIC BACTERIA
STARK EFFECT
PHOTOSYNTHETIC REACTION CENTERS
ABSORPTION SPECTROSCOPY
ELECTRIC FIELDS
HISTIDINE
LEUCINE
PHENYLALANINE
PHOTOSYNTHESIS
AMINO ACIDS
AZOLES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
IMIDAZOLES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHYTOCHROMES
PIGMENTS
PORPHYRINS
PROTEINS
SPECTROSCOPY
SYNTHESIS
550201* - Biochemistry- Tracer Techniques