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Optically directed molecular transport and 3D isoelectric positioning of amphoteric biomolecules

Hafeman, Dean G. and Harkins, James B., IV and Witkowski, Charles E., II and Lewis, Nathan S. and Warmack, Robert J. and Brown, Gilbert M. and Thundat, Thomas (2006) Optically directed molecular transport and 3D isoelectric positioning of amphoteric biomolecules. Proceedings of the National Academy of Sciences of the United States of America, 103 (17). pp. 6436-6441. ISSN 0027-8424. http://resolver.caltech.edu/CaltechAUTHORS:HAFpnas06

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Abstract

We demonstrate the formation of charged molecular packets and their transport within optically created electrical force-field traps in a pH-buffered electrolyte. We call this process photoelectrophoretic localization and transport (PELT). The electrolyte is in contact with a photoconductive semiconductor electrode and a counterelectrode that are connected through an external circuit. A light beam directed to coordinates on the photoconductive electrode surface produces a photocurrent within the circuit and electrolyte. Within the electrolyte, the photocurrent creates localized force-field traps centered at the illuminated coordinates. Charged molecules, including polypeptides and proteins, electrophoretically accumulate into the traps and subsequently can be transported in the electrolyte by moving the traps over the photoconductive electrode in response to movement of the light beam. The molecules in a single trap can be divided into aliquots, and the aliquots can be directed along multiple routes simultaneously by using multiple light beams. This photoelectrophoretic transport of charged molecules by PELT resembles the electrostatic transport of electrons within force-field wells of solid-state charge-coupled devices. The molecules, however, travel in a liquid electrolyte rather than a solid. Furthermore, we have used PELT to position amphoteric biomolecules in three dimensions. A 3D pH gradient was created in an electrolyte medium by controlling the illumination position on a photoconductive anode where protons were generated electrolytically. Photoelectrophoretic transport of amphoteric molecules through the pH gradient resulted in accumulation of the molecules at their apparent 3D isoelectric coordinates in the medium.


Item Type:Article
Additional Information:Copyright © 2006 by the National Academy of Sciences Edited by Calvin F. Quate, Stanford University, Stanford, CA, and approved February 24, 2006 (received for review November 14, 2005). Published online before print April 17, 2006, 10.1073/pnas.0509881103 We thank Dr. Ring-Ling Chen for assistance and advice in construction of experimental equipment; Dr. Rubye Farahi for assistance in preparation of thin-film materials; Dr. Greg Hurst for assistance with MALDI mass spectrometry; and Drs. Kilian Dill, Bruce Jacobsen, Evelyn McGown, David Hachey, Richard Caprioli, Alfred Yergy, and Michael Sailor for helpful advice and assistance. This work was conducted under a cooperative research and development agreement between UT-Battelle and Protein Discovery, Inc., and was supported by National Institute on Drug Abuse Small Business Innovation Research Contract N43DA-3-7735 (to Protein Discovery, Inc.). In addition, partial support was received from the U.S. Department of Energy Office of Biological and Environmental Research and Environmental Management Science Program (T.T.). Oak Ridge National Laboratory is managed by UT-Battelle for the U.S. Department of Energy under contract DE-AC05-00OR22725. Author contributions: D.G.H., J.B.H., C.E.W., N.S.L., R.J.W., G.M.B., and T.T. designed research; D.G.H., J.B.H., and C.E.W. performed research; D.G.H., J.B.H., N.S.L., R.J.W., G.M.B., and T.T. contributed new reagents/analytic tools; D.G.H., J.B.H., C.E.W., N.S.L., R.J.W., G.M.B., and T.T. analyzed data; and D.G.H. wrote the paper. Conflict of interest statement: D.G.H., J.B.H., C.E.W., and N.S.L. own either stock or stock options in Protein Discovery, Inc., which holds a license to a patent application pending in the U.S. Patent Office that may cover portions of the technology described in this paper. G.M.B. and T.T. are listed coinventors on the subject patent application. In addition, R.J.W., G.M.B., and T.T. are employed at the Oak Ridge National Laboratory by its contractor, UT-Battelle, which is the assignee of the subject patent application. This paper was submitted directly (Track II) to the PNAS office.
Subject Keywords:electrophoresis; light; mass spectrometry; protein transport; proteomics
Issue or Number:17
Record Number:CaltechAUTHORS:HAFpnas06
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:HAFpnas06
Alternative URL:http://dx.doi.org/10.1073/pnas.0509881103
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5413
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:16 Oct 2006
Last Modified:14 Nov 2014 19:19

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