Biophysical Journal 88 2

Cover picture: Optical highlighting of DsRed variants in mammalian cells. (Top) Confocal image of a single HT-1080 cell expressing mitochondrially targeted DsRed[N42Q] after exposure of a subcellular region to femtosecond irradiation (λEX = 750 nm) to illustrate the localized red-to-green color change in fluorescence emission. Higher magnification images before and after “optical highlighting” demonstrate the lack of effect of “greening” on mitochondrial morphology (overlay). (Bottom) Confocal images before (left) and after (t = 0, middle) exposure of the right-hand portion of the cell to multiphoton excitation. (Right) Image captured ∼5 min later shows equilibration of the color gradient by diffusional mixing throughout the cytoplasm, but not within nuclear lobes (arrows). See the article by Robinson and Marchant on page 1444.