ABSTRACT
In the eld of membrane lipid and protein dynamics, uorescence recovery after photobleaching (FRAP) and single-particle tracking methods have provided ample evidence that lipids and proteins could have their motion restricted by interaction with other lipids and with the cell cytoskeleton.1-8 Fluorescence correlation spectroscopy (FCS) is a relatively new method in this eld that has received particular attention recently because of the possible combination with super-resolution microscopy methods.9-14 In this context, the use of very small volumes of excitation or variable volumes of excitation15 was considered necessary to unravel to transport of molecules at the nanoscale. However, most of the FCS studies done so far are based on the original idea of measuring temporal correlation at a single point in the membrane. Measuring a single location in the membrane is restrictive since the temporal uctuations at one point cannot reveal local microstructures or the anisotropic molecular transport in membranes. In this contribution, we discuss uctuation methods based on spatial correlation that reveal the dynamics of membrane lipids and proteins at the nanoscale.16-27 We show here that spatial correlations intrinsically contain more information than the classical temporal correlation rst introduced with the single-point FCS. Spatiotemporal correlation approaches have the
10.1 Introduction .................................................................................................. 215 10.2 The Autocorrelation Function....................................................................... 218 10.3 The Principle of Scanning FCS .................................................................... 219 10.4 The RICS Principle ....................................................................................... 223 10.5 The iMSD Concept and the Generalization of Fluctuation Correlation
Experiments .................................................................................................. 227 10.6 Example of Studies of Membrane Lateral Diffusion That Emphasize
the Spatial Correlation Method .................................................................... 231 10.7 Conclusions ...................................................................................................234 Acknowledgments .................................................................................................. 235 References .............................................................................................................. 235
potential to shift the paradigm in the use and kind of information that can be derived from uctuation methods for membrane studies. Also, spatiotemporal correlation can complement single-particle tracking experiments with much higher sensitivity and faster time scale.
