Conformational changes of individual fluorescently labeled proteins can be followed in solution using a confocal microscope. Two fluorophores attached to selected domains of the protein report fluctuating conformations. Based on Förster resonance energy transfer (FRET) between these fluorophores on a single protein, sequential distance changes between the dyes provide the real time trajectories of protein conformations. However, observation times are limited for freely diffusing biomolecules by Brownian motion through the confocal detection volume. A. E. Cohen and W. E. Moerner have invented and built microfluidic devices with 4 electrodes for an Anti-Brownian Electrokinetic Trap (ABELtrap). Here we present an ABELtrap based on a laser focus pattern generated by a pair of acousto-optical beam deflectors and controlled by a programmable FPGA chip. Fluorescent 20-nm beads in solution were used to mimic freely diffusing large proteins like solubilized F_oF₁-ATP synthase. The ABELtrap could hold these nanobeads for about 10 seconds at the given position. Thereby, observation times of a single particle were increased by a factor of 1000.

Date Published: 22 February 2013
PDF: 11 pages
Proc. SPIE 8587, Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues XI, 85870L (22 February 2013); doi: 10.1117/12.2002952

Published in SPIE Proceedings Vol. 8587:
Imaging, Manipulation, and Analysis of Biomolecules, Cells, and Tissues XI
Daniel L. Farkas; Dan V. Nicolau; Robert C. Leif, Editor(s)