Ultrabright photoactivatable fluorophores created by reductive caging

Application of advanced fluorescence microscopy to the structure of meiotic chromosomes

Chromosomes undergoing meiosis are defined by a macromolecular protein assembly called the synaptonemal complex which holds homologs together and carries out important meiotic functions. By retaining the molecular specificity, multiplexing ability, and in situ imaging capabilities of fluorescence microscopy, but with vastly increased resolution, 3D-SIM and other superresolution techniques are poised to make significant discoveries about the structure and function of the synaptonemal complex. This review discusses recent developments in this field and poses questions approachable with current and future technology.

Zooming in on biological processes with fluorescence nanoscopy

Fluorescence nanoscopy enables the study of biological phenomena at nanometer scale spatial resolution. Recent biological studies using fluorescence nanoscopy have showcased the ability of these techniques to directly observe protein organization, subcellular molecular interactions, structural dynamics, electrical signaling, and diffusion of cytosolic proteins at unprecedented spatial resolution. Super-resolution imaging techniques critically rely on bright fluorescent probes such as organic dyes or fluorescent proteins. Recently, these methods have been extended to live cells and multicolor, three-dimensional imaging, thereby providing exquisite spatiotemporal resolutions of the order of 10-20 nm and 1-2 s for subcellular imaging. Further improvements in image processing algorithms, labeling techniques, correlative microscopy, and development of advanced fluorescent probes will be required to achieve true molecular-scale resolution using these techniques.

Correlative microscopy of individual cells: sequential application of microscopic systems with increasing resolution to study the nuclear landscape

The term correlative microscopy denotes the sequential visualization of one and the same cell using various microscopic techniques. Correlative microscopy provides a unique platform to combine the particular strength of each microscopic approach and compensate for its specific limitations. As an example, we report results of a correlative microscopic study exploring features of the nuclear landscape in HeLa cells. We present a detailed protocol to first investigate distinct structural features of a living cell in space and time (4D) using spinning disk laser scanning microscopy (SDLSM). Then, after fixation and staining of selected structures (e.g., by means of immunodetection), details of these structures are explored at increasingly higher resolution using three-dimensional (3D) confocal laser scanning microscopy (CLSM); super-resolution fluorescence microscopy, such as three-dimensional structured illumination microscopy (3D-SIM); and transmission electron microscopy (TEM). We discuss problems involved in the comparison of images of a given cell nucleus recorded with different microscopic approaches, which requires not only a compensation for different resolutions but also for various distortions.