Analytical (force-measuring) optical tweezers have been used in a variety of applications ranging from micro-rheology to the study of colloidal hydrodynamics and nonequilibrium thermodynamics. Further, they have developed into a powerful tool in molecular biology, biochemistry, and biophysics, where they are used to manipulate and interrogate individual molecules. Force is involved in many facets of cellular life, ranging from the transport of cellular cargo by motors, such as myosin, kinesin, and dynein to the strain induced on an enzyme and its substrate during catalysis. With the ability to apply forces on individual molecules and measure the forces generated in their chemical reactions, analytical optical tweezers are ideally suited to investigate such mechanochemical transformations.
Currently, very few analytical tweezers are available to researchers. Such traps are typically made on massive optical tables and run in quiet basement rooms. Construction usually requires collaboration of a physicist (optics design), an electrical engineer (data acquisition, software) and an architect (ultra-stable room). When the instrument finally works, sometimes after years of development, a user scientist can begin to explore appropriate scientific questions. Here we expedite this process by providing a proven and detailed design for an analytical optical trap. The ideal design should be easy to build in a university machine shop and have a low cost in terms of parts, placement and operation.
Our current design has the following features:
Force resolution: sub-piconewton
Distance resolution: sub-nanometer
Time resolution: 1 millisecond
Wavelength: 845 nm
Max Force: 150 pN
Weight: 8 kilograms, hangs from a bungee cord
Placement: sound-proof box in normal lab (no basement required)
Parts cost: $35,000
Machining cost: $8,000 (with department subsidy)