Molecular Size Scissors Powered by Light

A group of researchers at the University of Tokyo have developed a pair of molecular-scale scissors that open and close in response to light. "They measure just three nanometers in length, small enough to deliver drugs into cells or manipulate genes and other biological molecules", says Takuzo Aida, Ph.D., professor of chemistry and biotechnology.

Using a photo-responsive chemical group that extends or folds when light of different wavelengths falls upon it, they consist of a pivot, blades and handles.

The pivot part of the scissors is a double-decker structure made of chiral ferrocene, with a spherical iron (II) atom sandwiched between two carbon plates.

The three-piece unit creates a shaft that allows the scissors to rotate and swivel.

Responsible for the motion are two handles strapped with photo-responsive molecules called azobenzene, which not only has the ability to absorb light, but comes in two isomeric forms: a long-form and short-form.

Upon exposure to UV light and visible light alternatively, the long-form is converted into the short-form, and exposure to visible light transforms it into the long-form again, this increase-decrease in length driving the handles in an open-close motion that activates the pivot, followed by an opening-closing motion of the blades.

As the blades open and close, the guest molecules remain attached to the zinc porphyrin, and as a result, they are twisted back and forth.

It is known, for example, that near-infrared light can reach deep parts of the body, thus, by using a multi-photon excitation technique, the scissors can be manipulated in the body for medicinal applications such as gene delivery.

The development of such techniques would have applications in biology and medicine because it would provide scientists with a simple way to manipulate genes and other molecules.

Further research on the subject is hoped to develop larger scissors, that could be remotely operated, but practical applications may require another 10 years or so.