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Nano-optical Tweezers Make Single-Molecule Protein Study Easier

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Laser tweezers could eventually replace fluorescence imaging in applications such as studying heterogeneity in virus populations and nanoparticle manipulation.

A nano-optical tweezer, developed at the University of Victoria, facilitates the capture and analysis of individual proteins. It also enables single-protein interactions with small-molecule drugs and DNA. It builds on existing optical tweezer techniques, which use a single-beam laser directed through an objective lens to trap and manipulate micron-sized particles and image them in 3-D.


The double nanohole optical tweezer uses a standard inverted microscope and a nanofabricated metal film. Images courtesy of SPIE. 


Fluorescence labeling has long been used in such work, but has downsides including bleaching, low signal and disruption of biomolecules’ natural state. Fixing these requires expensive processing and instrumentation, researchers said.

The new tweezer operates for an extended time and uses only the trapped object’s intrinsic light scattering. Additionally, the device offers a label-free, single-molecule, low-cost approach that operates in free solution without the need for tethers, which the researchers said can disrupt molecular motion and block potential binding sites of proteins and small molecules.

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The researchers have found that a double nanohole aperture makes the new nano-optical tweezer more efficient than traditional techniques, and has enabled them to achieve trapping even with low laser power. This aperture uses a conventional inverted microscope laser-trapping system.    


Variations in laser-scattering autocorrelation show binding-induced changes to the molecular dynamics of the protein.


While some trapping techniques use surface plasmon resonance, the researchers note that this aperture does not, resulting in lower heat and energy consumption.

The new tweezer also enables dielectrostriction, a pulling force capable of unfolding proteins and studying them in real time. The technique also could be adapted for DNA sequencing.

The research is published in SPIE Newsroom/Nanotechnology (doi: 10.1117/2.1201405.005494). 

For more information, visit www.uvic.ca.

Published: May 2014
Glossary
fluorescence
Fluorescence is a type of luminescence, which is the emission of light by a substance that has absorbed light or other electromagnetic radiation. Specifically, fluorescence involves the absorption of light at one wavelength and the subsequent re-emission of light at a longer wavelength. The emitted light occurs almost instantaneously and ceases when the excitation light source is removed. Key characteristics of fluorescence include: Excitation and emission wavelengths: Fluorescent materials...
nano
An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
nanoparticle
A small object that behaves as a whole unit or entity in terms of it's transport and it's properties, as opposed to an individual molecule which on it's own is not considered a nanoparticle.. Nanoparticles range between 100 and 2500 nanometers in diameter.
optical tweezers
Optical tweezers refer to a scientific instrument that uses the pressure of laser light to trap and manipulate microscopic objects, such as particles or biological cells, in three dimensions. This technique relies on the momentum transfer of photons from the laser beam to the trapped objects, creating a stable trapping potential. Optical tweezers are widely used in physics, biology, and nanotechnology for studying and manipulating tiny structures at the microscale and nanoscale levels. Key...
AmericasBiophotonicsBioScanCanadaDNAfluorescencelensesMicroscopymoleculenanonanoparticleOptical trappingoptical tweezersOpticsResearch & Technologysingle proteintethersUniversity of Victorianano-optical tweezerdielectrostrictionLasers

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