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Determination of the Stiffness of Skeletal Actomyosin Cross-Bridges by Optical tweezers (OT) (CAT#: STEM-MB-1314-WXH)

Introduction

Many types of cellular motility, including muscle contraction, are driven by the cyclical interaction of myosin with actin, coupled to the breakdown of ATP. The current view of the mechanism is that myosin binds to actin with the products of ATP hydrolysis (ADP and phosphate) bound in the catalytic site (cross-bridge attachment). Then, as the products are released, myosin changes conformation to produce a movement or “working stroke”. In the absence of nucleotide, actin and myosin form a tightly bound “rigor” complex. Binding of a new ATP molecule to myosin causes the rigor complex to dissociate (cross-bridge detachment), and subsequent ATP hydrolysis resets the original myosin conformation so that the cycle can be repeated.




Principle

Optical tweezers (originally called single-beam gradient force trap) are scientific instruments that use a highly focused laser beam to hold and move microscopic and sub-microscopic objects like atoms, nanoparticles and droplets, in a manner similar to tweezers. If the object is held in air or vacuum without additional support, it can be called optical levitation.
The laser light provides an attractive or repulsive force (typically on the order of piconewtons), depending on the relative refractive index between particle and surrounding medium. Levitation is possible if the force of the light counters the force of gravity. The trapped particles are usually micron-sized, or even smaller. Dielectric and absorbing particles can be trapped, too.

Applications

• Optical tweezers are used in biology and medicine (for example to grab and hold a single bacterium, a cell like a sperm cell or a blood cell, or a molecule like DNA).
• Nanoengineering and nanochemistry (to study and build materials from single molecules).
• Quantum optics and quantum optomechanics (to study the interaction of single particles with light).

Procedure

1.Sample preparation
2.Force Calibration
3.Measurement
4.Analysis

Materials

Optical tweezers
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