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1.
Fig. 3

Fig. 3. From: Controlling Brownian motion of single protein molecules and single fluorophores in aqueous buffer.

Detection path for the hardware-feedback ABEL trap.

Adam E. Cohen, et al. Opt Express. ;16(10):6941-6956.
2.
Fig. 10

Fig. 10. From: Controlling Brownian motion of single protein molecules and single fluorophores in aqueous buffer.

Trapping of Cy3. a) Molecular structure of Cy3. The molecular weight is 507 g/mol. b) Histogram of count-rates in the trapping region, with no feedback, feedback, and anti-feedback. c) Representative time-traces with and without feedback. d) Autocorrelation of the intensity with no feedback, feedback, and anti-feedback.

Adam E. Cohen, et al. Opt Express. ;16(10):6941-6956.
3.
Fig. 6

Fig. 6. From: Controlling Brownian motion of single protein molecules and single fluorophores in aqueous buffer.

Feedback voltages as a 100 nm fluorescent bead is scanned through the trapping region. Blue: feedback voltage along the scan axis; green: voltage perpendicular to the scan axis. The sensitivity in this case is 0.76 V/μm and the noise is .

Adam E. Cohen, et al. Opt Express. ;16(10):6941-6956.
4.
Fig. 8

Fig. 8. From: Controlling Brownian motion of single protein molecules and single fluorophores in aqueous buffer.

Measurement of the mobility of a trapped 100 nm bead. a) The position of the trap center was modulated with a square wave of increasing amplitude and the cycle-average voltage was recorded. b) The area under the voltage vs. time curve is proportional to the mobility.

Adam E. Cohen, et al. Opt Express. ;16(10):6941-6956.
5.
Fig. 9

Fig. 9. From: Controlling Brownian motion of single protein molecules and single fluorophores in aqueous buffer.

Trapping of a single chaperonin in buffer. a) Time-lapse image of a single trapped molecule of GroEL (held for ~1.7 s). b) Histogram of the displacements of the molecule, extracted from the trajectory of video images. c) Photobleaching time-trace of trapped single molecules of the fluorescently labeled archeal chaperonin MmCpn. Discrete photo-bleaching steps are clearly visible.

Adam E. Cohen, et al. Opt Express. ;16(10):6941-6956.
6.
Fig. 2

Fig. 2. From: Controlling Brownian motion of single protein molecules and single fluorophores in aqueous buffer.

Excitation path for the hardware-feedback ABEL trap. a) Geometry of the excitation beam in the trapping region. We want the beam to propagate perpendicular to the trapping plane, and to have a confocal depth much greater than the depth of the trapping region. b) Optical setup to create the beam pictured in (a). Lens L1 has a focal length of f1 = 40 cm and lens L2 has a focal length of f2 = 18 cm.

Adam E. Cohen, et al. Opt Express. ;16(10):6941-6956.
7.
Fig. 4

Fig. 4. From: Controlling Brownian motion of single protein molecules and single fluorophores in aqueous buffer.

Fused silica microfluidic cell for the hardware-feedback ABEL trap. a) Macroscopic layout of the deep channels. The annular channel equalizes the hydrostatic pressure in the four arms of the trap, eliminating pressure-driven flows through the trapping region. b) Trapping region. The ends of the deep channels extend from the edges of the image. The wedges jutting from the corners are raised ~400 nm above the trapping region and set the depth of the trapping region. These wedges also act to focus the electric field into the center of the trapping region.

Adam E. Cohen, et al. Opt Express. ;16(10):6941-6956.
8.
Fig. 5

Fig. 5. From: Controlling Brownian motion of single protein molecules and single fluorophores in aqueous buffer.

Calibration of the ABEL trap performed by scanning a fixed 100 nm fluorescent bead through the trapping region. a) Scan in the x-y plane. The x and y feedback voltages are proportional to the respective offsets of the particle, and the total photon count rate is independent of the offset. b) Scan in the x-z plane. The x feedback voltage is proportional to the offset, with a gain that does not vary strongly with z. Within a large region, the photon count rate is independent of position.

Adam E. Cohen, et al. Opt Express. ;16(10):6941-6956.
9.
Fig. 7

Fig. 7. From: Controlling Brownian motion of single protein molecules and single fluorophores in aqueous buffer.

Trapping of a 100 nm bead in the hardware-feedback ABEL trap. a) Image of a trapped bead obtained by averaging 11 video frames (corresponding to 1 s of data). b) Histogram of voltages applied along the x-axis to keep the bead trapped. c) Impulse response function of the feedback electronics. The latency is dominated by the cruddy SR844 lock-in amplifier. d) Power spectrum of the voltage oscillations (blue), and fits based on including the effect of measurement noise (red), and without measurement noise (black).

Adam E. Cohen, et al. Opt Express. ;16(10):6941-6956.
10.
Fig. 1

Fig. 1. From: Controlling Brownian motion of single protein molecules and single fluorophores in aqueous buffer.

Schematic of the hardware-feedback ABEL trap. A two-dimensional acousto-optic beam deflector (AOBD) deflects a laser beam in a small circle at 40 kHz. The excitation light reflects of dichroic mirror DC and illuminates a particle in the trap. A bandpass filter BP blocks scattered excitation light while passing fluorescence. The tube lens TL focuses the fluorescence onto a pinhole PH, and the fluorescence photons are then detected by an avalanche photodiode (APD). Phase-sensitive detection of individual photons provides a sensitive indicator of the offset between the location of the particle and the center of the trap. A time-correlated single-photon counting module (PH 300) records the arrival time of each photon, and a beamsplitter BS diverts a small fraction of the fluorescence light toward a camera.

Adam E. Cohen, et al. Opt Express. ;16(10):6941-6956.

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