Magnetic bacteria probe for proteins.

Bacteria that fabricate magnetic particles use them as compasses to orient themselves to Earth's magnetic field (SN: 6/8/91, p. 367). Now, scientists are trying to use these bacterial magnets too-to separate proteins from a solution.

Researchers at the Tokyo University of Agriculture and Technology  have demonstrated a way to harvest magnetic particles from bacteria and attach them to antibodies that bind the mouse protein immunoglobulin G. After letting the particles attach to the protein in solution, the researchers use a magnet to pull the complex to the side of the container. Then, the scientists make the complex luminescent so they can identify it easily. They describe their work in the Oct. 15 Analytical Chemistry.

Magnetic particles are already being manufactured for these separation techniques, says Jim Richey of PerSeptive Biosystems in Framingham, Mass. For example, researchers have used manufactured particles to find fetal cells in maternal blood (SN: 11/2/96, p. 276).

Researchers have yet to synthesize particles as small as the ones bacteria make, however, manufactured particles are about 1 micrometer in diameter; bacterial particles are about one-tenth that size and therefore remain dispersed in a solution longer, says report coauthor Tadashi Matsunaga.