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Shining light on the fleeting interactions of single molecules

Date:
May 21, 2015
Source:
Department of Energy, Office of Science
Summary:
Scientists have devised a way of directly detecting and visualizing biomolecules and their changing association states in solution by measuring their size and charge characteristics while confined in a single-molecule trap.
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An anti-Brownian single-molecule microfluidic trap is used to observe individual light-harvesting antenna complexes in solution. The red laser beam flies over a pattern to track the position of the trimeric antenna protein shown and the grey arrows represent a snapshot of the feedback forces applied by the four electrodes. The spontaneous dissociation of the complex is directly visualized by measuring molecule-by-molecule size and charge characteristics in the trap. The panels show different stages in the dissociation of the trimeric antenna into monomers.
Credit: Image courtesy of Moerner Lab, Stanford University

Researchers have developed a method to directly detect and visualize individual biomolecules and their changing association states in solution by measuring their size and charge characteristics while confined in a single-molecule trap.

This method provides scientists a new, more direct way to measure binding and aggregation properties of single molecules in solution, and is applicable to numerous fields including biology, chemistry, materials science, and statistical physics and mechanics. Currently, the method is being used to assess the optical properties of photosynthetic antenna proteins in various states of assembly, and to measure other protein-protein interactions at the single-molecule level.

Many biological and chemical processes critically depend on molecules interacting in aqueous solution. However, watching these molecular encounter events is not easy due to the perpetual thermal agitation of the surrounding water molecules, and nanometer-sized biomolecules quickly diffuse out of the field-of-view of any conventional microscope. Building on the work that recently earned him a Nobel Prize in Chemistry, a Stanford University researcher used a microfluidic single-molecule trap to capture individual molecules in solution without any perturbations due to surface attachment. The trap compensates a single molecule's Brownian diffusive motion by continuously applying electric fields in solution that drive the molecule back to the center of the field-of-view.

While trapped, the molecule's residual movement can be precisely analyzed to yield size and charge sensitive motion parameters in real time (specifically, diffusion coefficient and mobility). Binding and dissociation events are directly visualized by fluctuations in those motion parameters. The methodology is demonstrated on two model systems: the time-dependent spontaneous dissociation of photosynthetic light-harvesting antenna complexes and direct observation of DNA strands binding and unbinding in solution.

This work was funded in part by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. Additional funding was provided by Stanford University.


Story Source:

Materials provided by Department of Energy, Office of Science. Note: Content may be edited for style and length.


Journal Reference:

  1. Quan Wang, W E Moerner. Single-molecule motions enable direct visualization of biomolecular interactions in solution. Nature Methods, 2014; 11 (5): 555 DOI: 10.1038/nmeth.2882

Cite This Page:

Department of Energy, Office of Science. "Shining light on the fleeting interactions of single molecules." ScienceDaily. ScienceDaily, 21 May 2015. <www.sciencedaily.com/releases/2015/05/150521081649.htm>.
Department of Energy, Office of Science. (2015, May 21). Shining light on the fleeting interactions of single molecules. ScienceDaily. Retrieved May 25, 2017 from www.sciencedaily.com/releases/2015/05/150521081649.htm
Department of Energy, Office of Science. "Shining light on the fleeting interactions of single molecules." ScienceDaily. www.sciencedaily.com/releases/2015/05/150521081649.htm (accessed May 25, 2017).

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