A double-trap optical tweezers instrument was constructed and its spatial resolution measured. The instrument features
real-time control that allows feedback based position- and force-clamping experiments. To study RNA-polymerization
by QDE-1, an RNA-dependent RNA-polymerase, we tethered a 7250 nt single-stranded DNA molecule between two
optically trapped microspheres. Preliminary constant-force extension trajectories and force-extension curves were
collected.
KEYWORDS: Optical tweezers, Digital signal processing, Signal detection, Calibration, Field programmable gate arrays, Signal processing, Feedback control, Data acquisition, Telescopes, Microscopes
Optically trapped microshperes can be manipulated by steering the trap beam, while the object position is measured with
sub-nanometer resolution. A fast steering system is required to create feedback loop for measurements at a constant force
or to increase position detection precision by trap stiffening. Using a real-time re-programmable digital signal processor,
we combine steering and position detection to create a fast and versatile closed-loop feedback controlled instrument. We
describe the construction and calibration of the instrument. We show that a proportional gain position-clamp algorithm
can achieve about 10-fold increase in effective trap stiffness while higher gains lead to unwanted resonances.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.