t's not exactly "ET, phone home," but MIT researchers reported in the Jan. 10 issue of Nature that they can "speak" to DNA biomolecules with radio waves.
The goal is to instruct biological materials how to act for a variety of purposes. Biological machines may one day be used to perform computation, assemble computer components or become part of computer hardware or circuitry. Radio-controlled biology may lead to single-atom or single-molecule machines, or the ability to hook tiny antennae into living systems to turn genes on and off.
"Recent studies have provided new insights into the complexity, precision and efficiency of biomolecular machines at the molecular scale, inspiring the development of physical and chemical manipulation of biological systems," said Joseph M. Jacobson, associate professor at the Media Lab and one of the paper's authors. "Manipulation of DNA is interesting because it has been shown recently that is has potential as an actuator (a hard drive component) and can be used to perform computational operations."
The researchers predict that radio frequency (RF) biology will have a broad range of applications. Because virtually all biological molecules can be linked with gold or other semiconducting nanoparticles, these molecules can be controlled electronically, remotely, reversibly and precisely, said Shuguang Zhang, associate director of the Center for Biomedical Engineering and another author of the study. Such systems will have profound implications for finely dissecting detailed molecular interactions and formations, he said.
SINGLE-ATOM MACHINES
Jacobson, head of the Media Lab's Molecular Machine group , has a background in quantum physics. He became interested in using biology as a tool to create nanometer-length machines. The ultimate goal, he said, is a single-atom or single-molecule machine.
It's hard to manufacture computer chips much smaller than 30 nanometers, but biology has an excellent track record at creating tiny workable systems. The cell itself is a phenomenal little machine with its own power supply and memory. "If we're interested in molecular-scale machines, biology is a wonderful place to start," Jacobson said.
He worked with researchers from the Center for Biomedical Engineering (CBE) to attach tiny radio-frequency antennae--a metal nanocluster of less than 100 atoms--to DNA. When a radio-frequency magnetic field is transmitted into the little antennae, the molecule is zapped with energy and responds.
Hybridization is the process of joining two complementary strands of DNA, or one each of DNA and RNA, to form a double-stranded molecule. In dehybridization, the strands unwind. Using this technique, the researchers dehybridized double-stranded DNA in a matter of seconds. The switching, which is reversible, did not affect neighboring molecules.
Nanocrystals can be attached to proteins as well as to nucleic acids. This opens the possibility of switching more complex processes such as enzymatic activity, biomolecular assembly, gene expression and protein folding. The function of cells' components and the cell life cycle itself may be electronically regulated with radio frequency, Jacobson said.
The goal is build molecules into systems that turn on and off depending on the electronic commands they receive. It may one day be possible to hook the antennae into living systems and turn genes on and off. "There are already numerous examples of nanocrystals attached to biological systems for the purpose of sensing," said co-author Kimberly Hamad-Schifferli, a postdoctoral associate in the MIT Media Lab. "However, we hadn't come across any examples where they are used as a means of controlling the biology."
"The development of molecular biology has witnessed many examples of ways to design new tools that accelerated uncovering nature's secrets," Zhang said. "Regulation of biomolecules using electronic RF control represents a new dimension in biology."
The exquisitely fine electronic controls of biological regulation will likely become more and more important in understanding complex molecular interactions in great detail, he said, because there is currently no other way to achieve fine local control without disturbing neighboring molecules. He likened the level of communication to using a mobile phone to convey a message to a single person in a crowd.
"Radio-frequency biology provides us with some extraordinary tools and with unprecedented precision controls to study biomolecules and their interactions. These new tools and technologies will undoubtedly advance our knowledge in finest detail. It not only opens new avenues for us to ask big and deep questions but also to attain the ultimate answers in biology," Zhang said.
In addition to Jacobson, Hamad and Zhang, the study's authors are John J. Schwartz, a former postdoctoral associate in the CBE who now works for engeneOS in Waltham, and Aaron Santos (S.B. 2001). Jacobson and Zhang also are affiliated with engeneOS, which designs and builds programmable biomolecular devices consisting of natural and non-natural materials for commercial applications.
This work is funded by the Defense Advanced Research Projects Agency (DARPA) and the Media Lab's Things That Think consortium .
A version of this article appeared in MIT Tech Talk on January 16, 2002.
