Under the microscope

The first commercial version of a new light microscope that allows cellular processes to be viewed at the smallest possible level of detail has been installed at the University of California Davis Center for Biophotonics Science and Technology.

The microscope - called OMX for Optical Microscopy eXperimental - will provide significant advantages to researchers seeking to understand and treat disease.

'OMX is a breakthrough technology in microscopy because it overcomes a long-standing barrier, the diffraction limit of light, to significantly increase the resolution of light microscopes,' said Dennis Matthews, the centre's director.

'The implications for medicine are profound, since the foundations of disease lie far deeper in cell structures than we can currently observe. With OMX, it is possible to see those cellular structures and how they 'talk' in real time.'

The diffraction limit has been an insurmountable barrier to medical researchers wanting to view cellular processes as they occur. Electron microscopes are high resolution but cannot be used to view living samples. Optical fluorescence microscopy allows imaging of live samples, but is relatively low resolution.

The new microscope, on the other hand, uses a new technique called structured illumination, which was invented by UCSF postdoctoral researcher Mats Gustafsson to overcome these limitations.

Structured illumination microscopy involves illuminating a sample with a pattern caused by interfering beams of light, rather than a single uniform beam. The illumination is achieved by passing incident light through a diffraction grating, then recombining the diffracted beams in the sample plane.

Emitted light from a sample so illuminated contains normally unobservable high-resolution information that has been shifted into an observable frequency range. By acquiring several images of shifted patterns at each section through the sample, high-resolution information can be separated and computationally re-shifted to its correct position in frequency space, leading to an increase in the resolution of the reconstructed image.

Since the OMX can produce rapid three-dimensional images of live samples in real time, researchers will be able to study cellular processes in action. UC Davis researchers are already planning to use the microscope in studies of traumatic brain injury and breast cancer.

The OMX was developed over the last five years at UCSF by professors John Sedat and David Agard. The project was supported by the biophotonics centre through a grant from the US National Science Foundation