Exploring molecular motors and switches at the single‐molecule level

Abstract

Single-molecule techniques have propelled an impressive number of biophysical studies during the last decade. From relatively simple video-microscopy techniques, to sophisticated manipulation and detection apparata, single-molecule techniques are capable of tracking the movements and the reaction trajectories of single enzymatic units. By observing microspheres attached to biomolecules it is possible to follow the motion of molecular motors, or to detect conformational "switching" induced by regulatory proteins. Micromanipulation tools like optical tweezers have been widely applied to understand the mechanisms of linear molecular motors, and have allowed the measurement of the elementary steps and the forces produced by several motor proteins, including myosin, kinesin, and dynein. New experimental assays based on magnetic or optical "wrenches," which are able to apply and detect torques on rotary motors and biopolymers, are opening new possibilities in this field. Here, established and emerging magneto-optical manipulation and video-tracking techniques are reviewed, in the perspective of single molecular motors and regulatory proteins studies.

The persistence length of double stranded DNA determined using dark field tethered particle motion

“…TPM has been used for a number of applications, including studying DNA-protein interactions, 14,15 DNA and RNA transcription, 16,17 looping and supercoiling of DNA, [18][19][20] and the determination of mechanical properties of DNA/RNA. [21][22][23] In these cases ͑except Ref.…”

Tethered particle motion mediated by scattering from gold nanoparticles and darkfield microscopy

“…It allows the study of biomolecules and biomolecular interactions in a fast and relatively easy way while retaining single molecule character. The achievement of TPM lies in its simplicity [12]. It allows one to look at many interactions simultaneously while maintaining single-molecule characteristics.…”

Light forces the pace: optical manipulation for biophotonics

“…Examples of the former include DNA and RNA polymerase, kinesin, and myosin V, and examples of the latter include myosin II. 77 The key difference is the number of steps along the bound polymer the motor takes; processive motors bind to a polymer chain and take many steps, and nonprocessive motors bind and take only approximately one step before dissociating.…”