As a preview to the forthcoming laboratory manual Imaging in Neuroscience, due in May, the current issue of Cold Spring Harbor Protocols highlights two articles on neuroscience imaging techniques.  The articles are freely accessible here and here.

Monitoring Individual Molecules with Quantum Dots

The first article details the use of nanometer-sized quantum dots (QDs) to track the motion of individual membrane molecules over time.  QDs possess strong fluorescence and photostability, permitting extended recording times compared to other methods.  In the article, authors Sabine Lévi, Maxime Dahan, and Antoine Triller (Ecole Normale Supérieure, Paris) provide step-by-step methods to stain neurons with QDs and to track QD-labeled molecules using single-fluorophore epifluorescence, as well as guidance for interpreting the data and reconstructing the trajectory of individual QD-labeled molecules.  These methods have been successfully used to follow the diffusion of individual glycine receptors, GABA receptors, NMDA receptors, lipid raft markers, glycophosphatidylinositol-anchored green fluorescent protein (GPI-GFP), and other molecules of interest.

Studying Specific Neural Activities with Microbial Opsins

The second article describes characteristics of various microbial opsins that are used in optogenetics.  Optogenetics is a revolutionary technology that combines optics and genetics to study very specific events, such as action potentials, in their natural context—even in freely moving mammals.  Microbial opsins are light-sensing proteins that regulate ion fluxes to control biological activities, and their corresponding genes can be expressed in mammalian neurons to enable millisecond-precision optical control of neural activity.  The authors of the article, Karl Diesseroth and colleagues (Stanford) and Peter Hegemann (Humboldt-Universität, Berlin), describe the diversity of microbial opsin genes, including those for bacteriorhodopsins, proteorhodopsins, halorhodopsins, and channelrhodopsins, and the structure-function properties of their corresponding proteins.  This overview will be useful to those looking to employ optogenetics as a research tool.