The relaxation of a single, 39 µm–long DNA molecule stained with YOYO®-1 iodide imaged at 4.5 second intervals.
The relaxation of a single, 39 µm–long DNA molecule stained with YOYO®-1 iodide (Cat. no. Y3601) imaged at 4.5 second intervals. After the 1 µm polystyrene sphere was trapped with optical tweezers, the attached DNA was stretched to its full extension in a fluid flow and then allowed to relax upon stoppage of fluid flow due to its entropic elasticity. (Science 264, 822 (1994)) The YOYO®-1 iodide–DNA complex is excited with the 488 nm spectral line of the argon-ion laser and visualized through a 515 nm longpass optical filter using a Hamamatsu SIT camera with image processing. Image contributed by Thomas Perkins, Stanford University.