Understanding the structure–function relationship of cells and organelles in their natural context requires multidimensional imaging. As techniques for multimodal 3-D imaging have become more accessible, effective processing, visualization, and analysis of large datasets are posing a bottleneck for the workflow. Here, we present a new software package for high-performance segmentation and image processing of multidimensional datasets that improves and facilitates the full utilization and quantitative analysis of acquired data, which is freely available from a dedicated website. The open-source environment enables modification and insertion of new plug-ins to customize the program for specific needs. We provide practical examples of program features used for processing, segmentation and analysis of light and electron microscopy datasets, and detailed tutorials to enable users to rapidly and thoroughly learn how to use the program.

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Removing the nucleus in sieve elements: Although a cell's nucleus performs critical command and control functions, some cell types, such as enucleated red blood cells, seem to do without. Sieve element cells in plants similarly carry out their function of transporting nutrients and signals from one end of the plant to the other without the guidance of a nucleus. Furuta et al. watched how the nucleus self-destructs during the development of sieve element cells (see the Perspective by Geldner). The process is regulated under the control of transcription factors, even as the entire nuclear edifice crumbles into nothingness. Science , this issue p. 933 ; see also p. 875

Cytochrome c oxidase catalyzes most of the biological oxygen consumption on Earth, a process responsible for energy supply in aerobic organisms. This remarkable membrane-bound enzyme also converts free energy from O ₂ reduction to an electrochemical proton gradient by functioning as a redox-linked proton pump. Although the structures of several oxidases are known, the molecular mechanism of redox-linked proton translocation has remained elusive. Here, correlated internal electron and proton transfer reactions were tracked in real time by spectroscopic and electrometric techniques after laser-activated electron injection into the oxidized enzyme. The observed kinetics establish the long-sought reaction sequence of the proton pump mechanism and describe some of its thermodynamic properties. The 10-μs electron transfer to heme a raises the pK _a of a “pump site,” which is loaded by a proton from the inside of the membrane in 150 μs. This loading increases the redox potentials of both hemes a and a ₃ , which allows electron equilibration between them at the same rate. Then, in 0.8 ms, another proton is transferred from the inside to the heme a ₃ /Cu _B center, and the electron is transferred to Cu _B . Finally, in 2.6 ms, the preloaded proton is released from the pump site to the opposite side of the membrane.