Date: Tuesday, February 25, 2014
Time: 11:00 am
Speaker: Prof. Ke Xu, UC Berkeley
Title: Super-Resolution Fluorescence Microscopy: New Biology Revealed by Sub-10 nm Resolution
Location: 67-3111 Chemla Room
Fluorescence microscopy is an indispensable tool for biology. It provides the distinct advantages of being noninvasive and molecular specific, and so permits the real-time observation of specific molecular targets in live cells with high contrast. A drawback of fluorescence microscopy, however, is its relative low resolution (~200-300 nm) due to the diffraction of light. The recent development of super-resolution fluorescence microscopy overcomes the diffraction limit through fundamentally redesigning how images are acquired and processed. In particular, we recently developed methods that achieved sub-10 nm optical resolution for biological samples. The improved resolution helped reveal exciting new structures in cells. In particular, in neurons we discovered a novel cytoskeleton structure that is highly ordered at the nanometer-scale. We found that actin filaments are arranged into ring-like structures in axons, and the rings are evenly spaced along the axon with a well-defined 190 nm spacing, resulting in a ladder-like, periodic lattice with long-range order. We further pinpointed the molecular mechanism underlying this novel structure: spectrin tetramers connect adjacent actin rings, thus regulating the periodicity of the lattice and forming a cohesive cytoskeleton. This novel, periodic cytoskeleton is only found in axons, and besides providing mechanical support for the membrane, it further arranges sodium ion channels, the signal generators of neurons, into similar periodic patterns along the axon.