Effect of fluorescamine modification of purple membranes on exciton coupling and light-to-dark adaptation

Eric Lam, Lester Packer

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Abstract

Purple membranes of Halobacterium, halobium were modified with fluorescamine. At pH 8.8, with a molar ratio of fluorescamine to bacteriorhodopsin of 170, about 6 residues of lysine were modified while the arginines were not affected at all. Except for the appearance of the fluorescamine peak at 394 nm and some broadening of the chromophore peak at 570 nm, the absorption spectrum of bacteriorhodopsin was not significantly changed after modification. After fluorescamine modification, circular dichroism studies indicated loss of exciton coupling between bacteriorhodopsin molecules in the purple membrane. Rotational diffusion studies suggested enhanced mobility of the chromophore after modification. However, the spectral changes accompanying the light-to-dark adaptation of purple membranes were not prevented by fluorescamine modification. The implications of these findings are that exciton coupling between neighboring bacteriorhodopsin molecules in the purple membrane is not required for light-to-dark adaptation.

Original languageEnglish (US)
Pages (from-to)464-471
Number of pages8
JournalBiochemical and Biophysical Research Communications
Volume101
Issue number2
DOIs
StatePublished - Jul 30 1981
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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