Research Program
Biomolecular Dynamics

Project #
BD4

Principal Investigators
Michelle D. Wang, Optical instrumentation
Ulrich Wiesner, Quartz/silica particle fabrication
Christopher Ober, Polymer particle fabrication
Michael Koonce, Dynein motility assay development

Project Summary
We propose to develop techniques that will enable the study of rotational motion in biological molecular motor systems and then to apply this technology to the study of biological motors such as dynein. The first part of the project, now largely complete, has been to develop a torque-enabled optical tweezers which can take advantage of the material anisotropy of quartz micro-particles to generate rotation and detect torque. This advance will give us the ability to study rotation of biological structures with the same level of precision and control currently available for the study of linear movement and force using conventional optical tweezers.

The next phase of the project is to develop a nano-fabricated particle which is compatible with the torque-enabled tweezers and which can be specifically attached to biomolecules. The fabrication of the particle is planned to proceed in several stages. Initial efforts will focus on using techniques developed in Prof. Weisner's laboratory to grow a carboxylated silica coating on quartz particles. A more ambitious phase will be to identify polypeptides that will make facet-specific attachment to the quartz microcrystals. If successful, this will allow us to attach biomolecules which are ideally positioned with respect to the axis of rotation of the quartz particles. An alternative approach will be to make cylindrical nano-particles by patterning of anisotropic polymer films.

Development of the optical apparatus will proceed concurrently with efforts to develop nano-fabricated particles. Up until now, the apparatus has been used solely to study torque generation and detection using free particles. The next step is to install a piezo electric nano-positioning stage and calibrate force generation and measurement using tethered particles. This would allow preliminary studies of dynein to begin using nonspecific attachment to polystyrene beads and conventional optical trapping techniques (force measurements).

We anticipate that efforts to coat quartz particles with silica will be completed rather quickly, which will allow us to proceed rapidly to the task of developing non-rotational attachments to biomolecules using arrays of tags on polypeptide chains or on double stranded DNA. Once the attachment is achieved, further development of the apparatus and control software will be required to address issues related to simultaneous measurement of force and torque. The ultimate goal of the project is to bring these techniques together and use them to measure force and torque generation in the molecular motors, such as dynein.

The project started 2 years ago with the past year supported by the NBTC. The project will continue for another 3 years.