Gramicidin in chromatophores of Rhodobacter sphaeroides |
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Authors: | G Althoff G Schönknecht W Junge |
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Institution: | (1) Biophysik, Fachbereich Biologie/Chemie, Universität Osnabrück, W-4500 Osnabrück, Germany;(2) Present address: Botanisches Institut I der Universität Würzburg, Mittlerer Dallenbergweg 64, W-8700 Würzburg, Federal Republic of Germany |
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Abstract: | Chromatophores of Rhodobacter sphaeroides were excited with light flashes to generate a transmembrane electrical potential difference. The electric relaxation was measured by electrochromic absorption changes as a function of added gramicidin. At low gramicidin/bacteriochlorophyll (BChl) molar ratios the decay of the electrochromic absorption changes showed a biphasic behaviour, with a fast phase relaxing at some s, and a slow phase relaxing at more than 100 ms. This was attributable to a mixture of vesicles containing gramicidin dimers with others containing none. The concentration dependence of this effect was linear. This implied full dimerization of gramicidin. The data were interpreted to yield an average bacteriochlorophyll content per chromatophore of 770(±150) and the conductance of a single gramicidin dimer in the chromatophore membrane of 15(±4) pS (in about 115 mM KCl).Abbreviations BChl
Bacteriochlorphyll
- tricine
N-Trishydroxymethyllmethylglycine
Offprint requests to: W. Junge |
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Keywords: | Photosynthesis Chromatophore Gramicidin Electrochromism Size analysis |
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