MAGNETIC CIRCULAR DICHROISM OF BACTERIOCHLOROPHYLL a IN SOLUTION AND IN A PROTEIN

John C. Sutherland, John Melvin Olson

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Abstract— The magnetic circular dichroism (MCD) (300–850nm) of the bacteriochlorophyll (Bchl) a‐protein from the green photosynthetic bacterium Prosthecochloris aestuarii 2 K is qualitatively similar to the MCD of Bchl a in methanol and ether solution. This result implies that the transition dipole of the lowest energy electronic transition (near 800 nm) is roughly perpendicular to the transition dipole of the next higher electronic band (near 600nm) for Bchl a molecules in the protein just as it is for molecules in solution. This result provides no support for the recent proposal that interactions with the protein rotates the direction of the transition dipoles of the 800nm band of all the Bchl a molecules in the protein by 90°. While a rotation of the 800nm transition dipoles cannot be rigorously excluded, it would be necessary for the postulated perturbation to rotate the transition dipoles of both the 800 and 600nm bands by 90°. In a broader sense, any postulated perturbation would have to be shown to leave both the absorption spectrum and the MCD largely unaffected. MCD is a more sensitive test than absorption spectroscopy for perturbations of electronic states and changes in the relative orientation of transitions, because it depends on both the magnitudes and directions of at least two electric and one magnetic transition dipole.

Original languageEnglish (US)
Pages (from-to)379-384
Number of pages6
JournalPhotochemistry and Photobiology
Volume33
Issue number3
DOIs
StatePublished - Jan 1 1981
Externally publishedYes

Fingerprint

Bacteriochlorophylls
Circular Dichroism
dichroism
dipoles
Molecules
Proteins
Electronic states
proteins
Absorption spectroscopy
perturbation
Ether
Methanol
Absorption spectra
Spectrum Analysis
Bacteria
electronics
molecules
bacteria
proposals
ethers

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry

Cite this

MAGNETIC CIRCULAR DICHROISM OF BACTERIOCHLOROPHYLL a IN SOLUTION AND IN A PROTEIN. / Sutherland, John C.; Olson, John Melvin.

In: Photochemistry and Photobiology, Vol. 33, No. 3, 01.01.1981, p. 379-384.

Research output: Contribution to journalArticle

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