title: Determination of the fractal dimension of membrane protein aggregates using fluorescence energy transfer.
abstract: It is demonstrated that fluorescence resonance energy transfer may be used to determine the fractal dimension of aggregates of membrane-bound proteins. Theoretical and experimental results are presented for two different experimental designs: energy transfer between proteins and energy transfer from lipids to proteins. For energy transfer between proteins the lattice spacing must be known independently for a fractal dimension to be uniquely determined, and this represents a disadvantage to this experimental design. Results are presented for the calcium ATPase and a fractal dimension of 1.9 is estimated for ATPase aggregates by assuming a lattice spacing of 50 A. Energy transfer from lipids to protein provides a means of estimating the length of the "coast-line" of the aggregate. In this case the fractal dimension is uniquely determined from a log-log plot. An analysis of data for bacteriohodopsin reconstituted in phospholipid vesicles gives a fractal dimension of 1.6. The structural basis of the value for the fractal dimension is discussed for these two systems. These techniques provide a means of assessing the nature of protein-protein interactions in membranous systems.
authors.affiliation: Department of Chemistry, University of Denver, Colorado 80208.
authors.forename: T G
authors.initials: TG
authors.lastname: Dewey
authors.forename: M M
authors.initials: MM
authors.lastname: Datta
mesh_terms: D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D004735:Energy Transfer; D005456:Fluorescent Dyes; D046911:Macromolecular Substances; D008433:Mathematics; D008565:Membrane Proteins / Q000378:metabolism*; D008962:Models, Theoretical; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D005456:Fluorescent Dyes; D046911:Macromolecular Substances; D008565:Membrane Proteins; D000252:Calcium-Transporting ATPases