In x-ray diffraction, a crystallized sample with billions of molecules scatters the x rays into a characteristic pattern of spots on a detector which is then decoded to yield lattice structure information.
A team of Japanese scientists have developed a method, which they call diffracted x-ray tracking (DXT), in which the bobbing Brownian motions of single nanocrystallites in water are watched by tracking scattered x rays; with this method, one acquires information not about the position, but about the rotary motion of single nanoparticles (See Sasaki et al., Physical Review E, September 2000).
Now the process has been extended to single DNA molecules, whose Brownian motion can be tracked, for the first time, with a precision of picometers, or 10^-15 m (see figure at this URL.)
The researchers will soon broaden their measurements of important biomolecules. For example, they hope to observe the structural changes accompanying the activation of ion channels in living cells. (Sasaki et al., Physical Review Letters, 10 December 2001; contact Yuji Sasaki, Japan Synchrotron Radiation Research Institute.
(Editor's Note: This story, with some editing, is based on PHYSICS NEWS UPDATE, the American Institute of Physics Bulletin of Physics News Number 568, December 7, 2001, by Phillip F. Schewe, Ben Stein and James Riordon.)