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A Practical Guide to Optical Trapping Joshua W. Shaevitz

Summary: A Practical Guide to Optical Trapping
Joshua W. Shaevitz
August 22, 2006
1 Introduction to optical trapping
In the last few decades, novel microscopy techniques have been developed to monitor the activity of single
enzymes as they perform their biological functions in vitro. Motor proteins such as kinesin, myosin, F1Fo
ATPase, and RNA polymerase have been mercilessly subjected to magnetic, elastic, and optical forces
[14, 40, 48, 16, 18]. In 1986, Ashkin and colleagues reported the first observation of a stable three-
dimensional optical trap, or optical tweezers, created using radiation pressure from a single laser beam
[4]. Only a few years later, Block and colleagues had used an optical trap to manipulate and apply forces to
E. coli flagella [8] and single kinesin motors [9]. Optical traps use light to manipulate microscopic objects
as small as 10 nm using the radiation pressure from a focused laser beam. In addition, measurement of
the light deflection yields information about the position of the object in the laser focus. Many excellent
reviews have been written about optical trapping, its uses, and designs, see e.g. [2, 6, 22, 27, 37, 38, 43]. In
particular, Lang and Block [23] is a thorough review of the optical trapping literature. This manuscript is
meant to be a practical guide to understanding optical traps, and not an in depth review. When possible,
simple examples and explanations are used to give the reader an intuitive feel for how these systems work
and how they are implemented. I hope that this document will continue to improve, and welcome any


Source: Asbury, Chip - Department of Physiology and Biophysics, University of Washington at Seattle


Collections: Biology and Medicine