Look inside a living cell
A revolutionary microscopy technique using three-dimensional structured illumination has allowed scientists at the University of California, working under the guidance of Professor John Sedat, to obtain a series of unprecedented, the most detailed to date, optical images of the functioning of the internal structures of cells.
The resolution of conventional light microscopes is limited by the fundamental properties of light: lenses do not allow you to see an object whose size is less than half the wavelength of radiation. Magnification of more than 2000 times is meaningless, because the image does not become more detailed, and the minimum size of objects visible in an optical microscope is about 200 nm. Much larger magnification can be achieved using electron microscopy and other non-optical methods, but they are applicable only to dead cells. Therefore, the interactions of DNA, RNA, proteins and other macromolecules occurring inside the cell still largely remain a mystery.
The resolution of the new microscope is about 100 nanometers. This is achieved by the fact that the cells are illuminated not by a beam of light, but by thin strips of light – an interference pattern. The reflection of this light by the smallest cellular structure, for example, by the accumulation of proteins inside the cell nucleus, slightly changes the interference pattern. Special software processes the reflected light recorded by the microscope and creates an image.
The authors made an important contribution to the development of a new technique originally intended for obtaining two-dimensional images. The next stage of the work will be to find a way to reduce the amount of light used, which will reduce the damaging effect on cells during microscopy.
The figure shows one of the three–dimensional images obtained using the new method: a cell in the process of division, immediately after the formation of two new nuclei (their shells are colored blue). Red grains are chromosomes, green filaments are microtubules of the protein tubulin, which pull the nuclei to opposite poles of the cell. A few more pictures can be viewed here.
To be fair, it should be noted that in recent years two more methods of optical microscopy have been developed, allowing to see even finer details in living cells.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of TechnologyReview
06.06.2008