While we use our hands for all our daily functions, most people don’t think about how our right and left hand are related to one another as mirror images. This relationship can also be applied to chiral molecules – molecules with an asymmetrical structure. When a chiral molecule is synthesized in the lab, its doppelganger, a mirror image of the intended molecule, is also made. The two may look similar but, like the right and left hand, they are not interchangeable.
This characteristic can have significant consequences. Let's use ibuprofen as an example. Depending on the “handedness” of a molecule, ibuprofen can be four times more potent. Another example is with the molecule limonene, which could go from smelling like oranges to smelling like turpentine.
Moore Foundation grantee Jennifer Dionne and colleagues at Stanford University and FOM Institute AMOLF in the Netherlands have developed a nanoscale filter that, when illuminated with a laser, attracts a molecule while repelling its mirror image. This new technique could someday be used to sort drugs to make them safer or more effective.
"Approximately 50 percent of drugs and 30 percent of agrichemicals are chiral, which means they can be left- or right-handed. Of those, more than 90 percent are sold as mixtures of both handed molecules because it’s so hard to separate them," said Dionne, an associate professor of materials science and engineering at Stanford.
Dionne's development of a new biological tool for optical trapping and manipulation of proteins and nucleic acids -- the core of her Moore Foundation grant -- has now shown promise for separating chiral molecules.
Focused light can change the momentum of an object. This effect has been used to create optical tweezers, which allow scientists to manipulate particles with highly focused beams of light. Although the idea of tweezing apart chiral forms is exciting, most molecules of interest are too small to be pulled apart by optical forces directly.
Yang Zhao, a postdoctoral fellow working with Dionne, overcame that weakness by creating a nanostructure that allows circularly polarized light to interact more strongly with small specimens. The light path in the nanostructure maps a spiral in one direction but not the other. Once the chiral light has passed through this path, it interacts with molecules that complement its shape and pulls those downward.
The researchers tested their prototype by measuring the forces exerted on chiral specimens. They showed that the optical forces produced by their tweezers are strong enough to separate certain chiral molecules.
The team has not yet tested the tweezers on actual chiral molecules, but Zhao has begun quantifying the forces they are able to apply to DNA and certain proteins. These chiral molecules have a specific handedness in nature but can be either handedness if produced in a lab.
The next step will be assembling their tweezers into a filter that can separate two forms of a drug or other molecules. In addition to sorting drugs to make them safer or more effective, the team thinks their tweezers could be put to other uses, such as monitoring the folding or unfolding of a protein or enabling light-mediated synthesis of chiral chemicals.
Read more information in Stanford News and find the full article in Nature Nanotechnology.
Message sent
Thank you for sharing.