'Micro-boxes' of water used to study single molecules

Jul 20, 2006

Researchers at the National Institute of Standards and Technology have demonstrated the use of water droplets as minuscule "boxes" for small numbers of biomolecules. The unusually simple containment method may enable easier experiments on single molecule dynamics and perhaps lead to the development of molecule-sorting devices that might be used for medical screening or biotechnology research.

The work was reported in the July 3 issue of Applied Physics Letters.

The NIST team creates the boxes by briefly shaking a mixture of water, the biomolecules to be studied, and a fluorocarbon medium. Water droplets form in the oily fluorocarbon and naturally encapsulate one to several biomolecules. The researchers then watch through a microscope while using infrared lasers as "optical tweezers" to manipulate and combine the droplets (dubbed "hydrosomes") inside a tiny chamber on a slide.

'Micro-boxes' of water used to study single molecules
Prodded by optical tweezers, two "hydrosomes" move together and fuse to mix their contents, in an experiment using water droplets as minuscule boxes for manipulating small numbers of biomolecules for nanobiochemistry. Credit: NIST

A green laser is then used to excite the molecules in individual droplets, and the light emissions over several seconds are analyzed to count the molecules and observe other phenomena. The researchers use two sets of optical tweezers to move droplets together to fuse them and mix their contents. The team demonstrated the technique by trapping and manipulating droplets encapsulating various molecules (including a delicate protein that survived the shaking process), detecting the fluorescence signal from dye and protein molecules, and observing the transfer of energy from one end of a specially treated DNA molecule to the other.

Water offers several advantages over other methods for containing single molecules, such as attaching them to surfaces or placing them inside liposomes (artificial cells). The water droplets can be held far from any surface that might interfere, can readily encapsulate biomolecules (which prefer being in water as opposed to the fluorocarbon medium), and can readily fuse together to mix molecules or rapidly change their chemical environment.

The water droplets currently average about 300 nanometers in diameter and contain volumes measured in quadrillionths of liters; research is continuing to improve methods for controlling droplet size for different applications.

Citation: J.E. Reiner, A.M. Crawford, R.B. Kishore, L.S. Goldner, K. Helmerson and M.K. Gilson. 2006. Optically trapped aqueous droplets for single molecule studies. Applied Physics Letters. July 3.

Source: National Institute of Standards and Technology

Explore further: Lightweight membrane can significantly reduce in-flight aircraft noise

Related Stories

Sizing up cells: Study finds possible regulator of growth

Mar 02, 2015

Modern biology has attained deep knowledge of how cells work, but the mechanisms by which cellular structures assemble and grow to the right size largely remain a mystery. Now, Princeton University researchers ...

Recommended for you

Thinner capsules yield faster implosions

16 hours ago

In National Ignition Facility (NIF) inertial confinement fusion (ICF) experiments, the fusion fuel implodes at a high speed in reaction to the rapid ablation, or blow-off, of the outer layers of the target ...

Direct visualization of magnetoelectric domains

19 hours ago

A novel microscopy technique called magnetoelectric force microscopy (MeFM) was developed to detect the local cross-coupling between magnetic and electric dipoles. Combined experimental observation and theoretical ...

Upside down and inside out

20 hours ago

Researchers have captured the first 3D video of a living algal embryo turning itself inside out, from a sphere to a mushroom shape and back again. The results could help unravel the mechanical processes at ...

Heat makes electrons spin in magnetic superconductors

Apr 24, 2015

Physicists have shown how heat can be exploited for controlling magnetic properties of matter. The finding helps in the development of more efficient mass memories. The result was published yesterday in Physical Review Le ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.