Manipulation of objects on a microscopic scale can be done conveniently with a device known as a laser or optical tweezers. While laser trapping was originally devised for trapping Rayleigh particles (i.e. particles much less than the wavelength of the incident light) it's ability to manipulate biological particles such as macromolecules, viruses, microtubles and chromosomes offers great practical potential. Many systems of interest require multiple optical traps and several methods have been developed to achieve multiple trap configurations. However currently available trapping systems can produce at most only a few independent traps. Recently, Grier and Dufresne conceived of a new solution for achieving a multi-trap system. In their method a hologram is used to alter a single laser beam's wavefront. The wavefront is altered so that the downstream laser beam forms a large number of individual laser beams with relative positions and directions of travel fixed by the exact nature of the hologram. The hologram can be calculated from a user specified pattern of desired trap positions. Currently a laboratory device has been fabricated. This device has demonstrated the ability create the holograms and to trap multiple (up to 200) particles in any chosen pattern. We propose developing a commercial version of the holographic optical tweezers (HOT) along with a sample chamber suitable for introducing, manipulating and collecting specimen. We will also provide examples of how to apply HOT to the study of biological systems. One detailed example will be the study of receptor-agonist binding which could be extended to any system of interacting macromolecules such as antibody-antigen reactions. A second example will involve the evaluation of the bending moments of sickle cell hemoglobin fibers which are responsible for sickle cell anemia. Similar studies could be carried out on actin and myosin filaments and microtubles. Other potential applications will also be discussed briefly.
