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The structure of chromatophores from purple photosynthetic bacteria fused with lipid‐impregnated collodion films determined by near‐field scanning optical microscopy
Author(s) -
Shinkarev Vladimir P,
Brunner Robert,
White Jeffrey O,
Wraight Colin A
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00630-4
Subject(s) - collodion , chromatophore , membrane , nitrocellulose , fusion , chemistry , biophysics , substrate (aquarium) , lipid bilayer , blisters , vesicle , fluorescence , materials science , chemical engineering , optics , biology , biochemistry , composite material , ecology , linguistics , philosophy , physics , fishery , engineering
Lipid‐impregnated collodion (nitrocellulose) films have been frequently used as a fusion substrate in the measurement and analysis of electrogenic activity in biological membranes and proteoliposomes. While the method of fusion of biological membranes or proteoliposomes with such films has found a wide application, little is known about the structures formed after the fusion. Yet, knowledge of this structure is important for the interpretation of the measured electric potential. To characterize structures formed after fusion of membrane vesicles (chromatophores) from the purple bacterium Rhodobacter sphaeroides with lipid‐impregnated collodion films, we used near‐field scanning optical microscopy. It is shown here that structures formed from chromatophores on the collodion film can be distinguished from the lipid‐impregnated background by measuring the fluorescence originating either from endogenous fluorophores of the chromatophores or from fluorescent dyes trapped inside the chromatophores. The structures formed after fusion of chromatophores to the collodion film look like isolated (or sometimes aggregated, depending on the conditions) blisters, with diameters ranging from 0.3 to 10 μm (average ≈1 μm) and heights from 0.01 to 1 μm (average ≈0.03 μm). These large sizes indicate that the blisters are formed by the fusion of many chromatophores. Results with dyes trapped inside chromatophores reveal that chromatophores fused with lipid‐impregnated films retain a distinct internal water phase.