ATTACHING A SINGLE DNA MOLECULE TO A SILICON SURFACE can now be done with heat instead of chemicals (which are usually specific to certain surfaces or sites), promising a more general and powerful method for depositing single DNA molecules onto specific locations on silicon chips. Such "DNA chips" are expected to provide a new approach to developing bio-sensors or bio-electronic circuitry. Researchers at Rockefeller University (G.V. Shivashankar, shiva@athena.rockefeller.edu, phone 212-327- 8160) first attach a single DNA molecule to a latex bead in water. They then use a focused laser beam known as an "optical tweezer" to trap the bead and hold the DNA molecule in place. Next an atomic force microscope tip comes in contact with the bead. Meanwhile, the laser stays on in order to attach the bead to the probe tip. The composite tweezer-and-AFM tool allows great manipulation flexibility, retains the biological functionality of the DNA, and offers the possibility of studying DNA and protein interactions (Applied Physics Letters, 22 Dec 1997).