Laser Trap: Optical Tweezers (IMAGE) Technical University of Munich (TUM) Caption An essential tool for TUM physicists' single-molecule studies of protein folding is their ultra-stable, high-resolution "optical tweezers," which can trap minuscule objects between opposing laser beams as surely as if they were being held between thumb and forefinger. To get a grip on a single calmodulin molecule, researchers first insert it between two molecules of a mechanically tougher protein called ubiquitin. Residues of the amino acid cysteine at the outer ends of this assembly allow "handles" made of DNA to be attached, and these are fixed to beads one micrometer in diameter. The beads, and thus the calmodulin molecule between them, can then be manipulated with the optical tweezers. Credit Image by Johannes Stigler, Copyright TU Muenchen Usage Restrictions This image may be freely used, with copyright noted, in news coverage of the Technische Universitaet Muenchen. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.