Linear Dichroism of Biological Chromophores

Hofrichter, James; Eaton, William A.

doi:10.1146/annurev.bb.05.060176.002455

Cited by 113 publications

(71 citation statements)

References 156 publications

(290 reference statements)

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“…Linear dichroism (LD) constitutes an alternative method. The ␣, ␤, and ␥ optical absorbance bands of Cyt c are known to correspond to electronic transitions lying in the heme plane (31), a conclusion tentatively extended to other hemes (32). Each of these bands corresponds, in many but not all cases (33), to the overlap of two transitions.…”

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confidence: 88%

“…The directions of the two transitions in the plane of the heme are not known with certainty but have been proposed to lie along the X and Y Fe-pyrrole ring directions (34,35). Bacteriochlorophylls (BChl) and chlorophylls (Chl) lack the high degree of symmetry of porphyrins, and the absorbance bands associated with different directions in the plane of the chlorin ring are therefore always distinct (32,36).…”

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confidence: 99%

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On the Spatial Organization of Hemes and Chlorophyll in Cytochrome b 6 f

Schoepp¹,

Chabaud²,

Breyton³

et al. 2000

Journal of Biological Chemistry

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The organization of chromophores in the cytochrome b 6 f from Chlamydomonas reinhardtii has been studied spectroscopically. Linear dichroism (LD) measurements, performed on the complex co-reconstituted into vesicles with photosynthetic reaction centers as an internal standard, allow the determination of the orientations of the chromophore with respect to the membrane plane. The orientations of the b H -and b L -hemes are comparable to those determined crystallographically on the cytochrome bc 1 . The excitonic CD signal, resulting from the interaction between b-hemes, is similar to that reported for the cytochrome bc 1 . LD and CD data are consistent with the differences between the b 6 f and bc 1 leaving the orientation of the b-hemes unaffected.

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confidence: 88%

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confidence: 99%

On the Spatial Organization of Hemes and Chlorophyll in Cytochrome b 6 f

Schoepp¹,

Chabaud²,

Breyton³

et al. 2000

Journal of Biological Chemistry

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“…Since the power spectrum of the pure flavin reveals nonzero absorbance beyond 530 nm, the observed polarization may arise from two perpendicular overlapping transitions, the in-plane flavin 7r -7r*, x, and the out-of-plane charge transfer, z . The expression for the polarization ratio becomes where t, and tz are the molar extinction coefficients for the x and z transitions (Hofrichter & Eaton, 1976). With data from two crystal faces, the internal consistency of various choices for x and z can be tested by using…”

Section: Imentioning

confidence: 99%

Molecular complex of lumiflavin and 2-aminobenzoic acid: crystal structure, crystal spectra, and solution properties

Shieh¹,

Ghisla²,

Hanson³

et al. 1981

Biochemistry

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ABSTRACT:The molecular complex lumiflavin-2-aminobenzoic acid monohydrate (C,3H,2N402C7H7N02-HZO) crystallizes from aqueous solution as red triclinic prisms. The space group is Pi with cell dimensions a = 9.660 A, b = 14.866 A, c = 7.045 A, a = 95-44', B = 95.86', and y = 105.66'. The crystal structure was solved by direct methods and refined by block-diagonal least-squares procedures to an R value of 0.050 on the basis of 1338 observed reflections. The structure is composed of stacks of alternating lumiflavin and un-ionized (neutral) 2-aminobenzoic acid molecules. Two different modes of stacking interaction are observed. In one, 2-aminobenzoic acid overlaps all three of the isoalloxazine rings, at a mean distance of 3.36 A; in the other, 2-aminobenzoic acid interacts with the pyrazine and dimethylbenzene moieties, at a distance (3) to two symmetrically related aminobenzoates; the water of crystallization forms three hydrogen bonds, bridging two flavins, via O(4) and N(5), and one aminobenzoic acid. The red color of the crystals results from a charge-transfer transition involving stacked flavin and 2-aminobenzoic acid molecules. Measurements of the polarized optical absorption spectra of crystals show that the transition moment direction for the long wavelength absorbance (beyond 530 nm) contains an out-of-plane component which can only arise from a charge-transfer interaction. Since the amino N does not make exceptionally close interactions with isoalloxazine atoms in either stacking mode (minimum interatomic distance 3.52 A), the charge transfer is presumed to involve T orbitals of the 2-aminobenzoic acid donor.

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“…Polarized absorption spectra of hemoglobin crystals provide information on the heme orientation in different ligation states (24,25). The pertinent parameter is the polarization ratio (PR), i.e.…”

Section: Resultsmentioning

confidence: 99%

“…Polarized light absorption along these directions obeys the Beer-Lambert law. The optical theory for myoglobin and hemoglobin crystals has been previously reported (18,24,25).…”

Section: Methodsmentioning

confidence: 97%