To probe the dynamics and size of lipid rafts in the membrane of living cells, the local diffusion of single membrane proteins was measured. A laser trap was used to confine the motion of a bead bound to a raft protein to a small area (diam # 100 nm) and to measure its local diffusion by high resolution...

The PFM is a three-dimensional scanning probe microscope based on optical tweezers. It evolved from AFM techniques by replacing the mechanical cantilever of the AFM with optical tweezers and the cantilever tip by a trapped bead. Various detection systems measure the three-dimensional position of the...

We show that the optical trapping of dielectric particles by a single focused beam in front of a weakly ref lective surface is considerably affected by interference of the incident and ref lected beams, which creates a standing-wave component of the total field. We use the two-photon-excited f luorescence...

We present a scanning probe microscope based on optical tweezers for three-dimensional imaging of the topology of transparent material in the nanometer range. A spherical nanoparticle serves as a probe. An optical trap moves it through the sample ~e.g., a polymer network!, while the position of the particle...

We show that the position of a f luorescent nanoparticle can be measured in three dimensions with subnanometer precision and 100-ms temporal resolution by use of standard epif luorescence video imaging in off-focus mode. The particle can be tracked without feedback in a volume of at least 40 mm 3 60...

We characterize the frequency-dependent response of a photo detection system based on a Si-PIN photodiode and a laser with wavelength 1064 nm, a system commonly used with optical tweezers. We chopped the laser beam with chopper frequencies from 200 Hz to 14 kHz, and found an exponentially delayed response...

A general method is presented for determining and correcting nonlinear position detector responses in single particle tracking as used in three-dimensional scanning probe microscopy based on optical tweezers. The method uses locally calculated mean square displacements of a Brownian particle to detect...

Traditional methods for cooling gases to close to absolute zero work only with a few of the elements. Two novel techniques together can cool down atoms of virtually any element, even some molecules. One of the techniques, which appears to break the second law of thermodynamics, is a physical realization...