While DNA may be the building block of life, it' s also becoming the building block of choice for nanoscientists who are redesigning it to perform a variety of tasks in everything from medicine to electronics. They' re tweaking the once-sacred double-helix to create new forms - pyramids and strands - that can serve as "nano-scaffolding" for molecular electronics, biosensors and gene repair.

Researchers at Ohio State University have devised a technique using a tiny rubber comb to pull DNA into long strands one nanometer wide and one millimeter long (a human hair of the same proportions would be thirty feet long). These strands could play a key role in the development of DNA computing because they promise a fast, inexpensive way to produce DNA circuitry. The team is already at work building these strands into sensors for detecting disease biomarkers and producing DNA-based nanoparticles for gene delivery.

Meanwhile, University of Oxford physicist Andrew Turberfield and his colleagues are busy building DNA pyramids using strands of synthetic DNA (see photo). They envision these structures being used as "nano-scaffolding" for 3D molecular electrical circuits or to house protein molecules in new methods of drug delivery.

A similar molecular cage has been developed at the Freie Universit�t Berlin using a complex molecule called HB-HPB that traps up to six atoms on a copper surface and transports them with the guidance of a scanning tunneling microscope.

And in a related breakthrough, biochemists and engineers at Jefferson Medical College and the University of Delaware are using carbon nanotubes coated with monoclonal antibodies to create guided protein missiles to detect cancer cells. Their technique, according to Balaji Panchapakesan, Ph.D., assistant professor of electrical engineering at the University of Delaware in Newark, " could be cost-effective and could diagnose whether cells are cancerous or not in seconds versus hours or days with histology sectioning. "

All of these advances take advantage of a basic principle of nanotechnology. At the molecular scale, structures like DNA can be manipulated to perform new functions like carrying other substances or transmit electricity. The restructuring of molecules to perform new tasks offers hope for new methods of diagnosis and treatment of cancer and similar breakthroughs. At the same time it concerns some people that we are now redesigning the most fundamental building blocks of life like DNA. Current restrictions on stem cell research in the US suggest that there are limits beyond which we are not willing to go, but DNA appears to be fair game. How long until we begin tweaking DNA to eliminate the transmission of debilitating diseases from generation to generation? How long until we alter it to avoid obesity, hair loss, or dissent?