Biophysical Journal 89 4

Cover picture: Spectral resonance energy transfer analysis (sRET): a new method for quantifying resonance energy transfer efficiency, in addition to donor and acceptor concentration. N1E cells were transfected with DNA encoding β-Cerulean (the Gβ1-subunit of trimeric G-proteins tagged with a blue CFP variant), γ-Venus (the Gγ2-subunit tagged with a yellow YFP variant), and unlabeled Gα0-subunits. Cells expressing these constructs were spectrally imaged with multi-photon excitation at two wavelengths, and processed using sRET analysis to produce a β-Cerulean image (top panel, left), a γ-Venus image (top panel, right), and a RET efficiency image (middle panel, left). A fluorescence lifetime image was also acquired and processed to produce a RET efficiency image for comparison (FLIM-RET, middle panel, right). RET efficiency distribution histograms were produced from the two RET efficiency images (bottom panel). See the article by Thaler et al. on page 2736.