April 12, 2006

Oak Ridge develops method for optically trapping and moving objects smaller than wavelength of light

A team from the Department of Energy's Oak Ridge National Laboratory, California Institute of Technology and Protein Discovery developed a new method to use a beam of light to trap protein molecules and make them dance in space The technique, called photoelectrophoretic localization and transport, or PELT, involves shining a highly focused beam of light on semiconductor material and using electric fields to move the proteins. Force-field traps are created by a photocurrent focused at the illuminated areas of the semiconductor. In contrast to traditional electrophoresis, which uses high voltage, this approach permits researchers to dynamically change characteristics of the electric field in three dimensions in real time using computer-controlled software and low voltage.

This new method also overcomes limitations of conventional optical trapping techniques, commonly called optical tweezers, which are versatile but unable to transport objects smaller than the wavelength of light. Included in this category are many biomolecules such as DNA fragments, oligonucleotides, proteins and peptides. Instead, such small molecules must first be attached to larger particles called "handles." This and other techniques have significant limitations, according to authors of the PNAS paper.

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