What studies have been developed from the topic presented in the seminar?

  • Optical tweezers have been used to determine forces produced by motor proteins to package DNA molecules into viral capsids.
  • Optical tweezers have also been used to investigate how molecular rearrangements lead to uneven walks of the recombinant kinesin motor constructs on microtubule.
  • A combination of PMR and oscillatory optical-tweezer-based AMR was used to explore the nonequilibrium mechanical behavior of biological polymers embedded with active motor proteins.
  • The deformation of red blood cells at the physiological level by multiple optical tweezers can be used to determine the relaxation of red blood cell recovery.

Impact on future

The application of material and mechanical science to the study of biological cells has a broader impact because material and mechanical properties of cells are very important to their function. We can use information from material and mechanical science to better understand how cells function and get a better understanding of the way that whole organs function.

Using microrheology, we can look at other cells as well as the endothelial cells that Dr. Ou-Yang focused on. We can look at neurons or gastrointestinal organs that have other functions in the body.

Under different conditions, optical tweezers can be used to measure the dynamics of protein binding to DNA, the force generated by a motor protein, the mechanical relaxation of a deformed red blood cell, the viscoelasticity of a fibroblast in suspension, whole-cell viscoelasticity, and local intracellular viscoelasticity.

With the advancement of new optical-tweezer-based experimental methods, along with high-resolution imaging techniques and theoretical development, we are seeing more progress in understanding how biological systems behave in mechanical environments.

Possible ethical issues of topic:

A possible ethical issue can be using this technique on live cells, moving cells within the body could possible cause cells to be altered and lead to problems in a living organism.

Sources:

Complex Fluids: Probing Mechanical Properties of Biological Systems with Optical Tweezers
H. Daniel Ou-Yang and Ming-Tzo Wei – Annual Review of Physical Chemistry – 2010

Additional Resources for Review

Further Papers by Dr. Ou-Yang:

Complex Fluids: Probing Mechanical Properties of Biological Systems with Optical Tweezers

“The mechanical properties of cells are crucial for cell sensing and reaction to mechanical environments. This review describes the basic principles of optical tweezers and their use as force sensors for studying the mechanical properties of biological systems. It covers experiments of four groups of biological systems arranged by increasing complexity: (a) packaging DNA into viral capsids by bacteriophage portal motors and the dynamical stiffness of DNA upon protein binding, (b) actin-coated giant vesicles and the myosin-II embedded actin polymer network, (c) suspension cells, and (d) adhesion cells. These examples demonstrate how optical tweezers have been used to improve the understanding of the mechanical properties of biological systems at subcellular and molecular levels.”

 Forces on a colloidal particle in a polymer solution: a study using optical tweezers

“We report a study of the dynamical behaviour of a polystyrene latex sphere in a telechelic poly(ethylene oxide) solution using optical tweezers. With this new technique, we use a position-sensing detector and a lock-in amplifier to measure the displacement magnitude and phase responses of one latex sphere driven sinusoidally by optical tweezers. For a single particle in solution, the equation of motion of the particle is simply that of the forced oscillation problem with damping from viscous drag and the restoring force from the elasticity of the solution medium and that of the optical tweezers. Because the system is overdamped, it is not feasible to probe the high-frequency regime. Thus we cannot measure the viscosity and elastic moduli separately from frequency-dependent measurements alone. At low polymer concentration, measurements of the viscosity have been achieved. We compared the measured viscosity with that obtained with other measurements. Key issues for further development of this technique, such as measuring the elastic modulus, are briefly discussed.”

Direct measurements of colloidal hydrodynamics near flat boundaries using oscillating optical tweezers

“We studied the hydrodynamic interaction between a colloidal particle close to flat rigid boundaries and the surrounding fluid using oscillating optical tweezers. A colloidal particle located near walls provides a model system to study the behavior of more complex systems whose boundaries can be modeled as effective walls, such as a blood tube, cell membrane, and capillary tube in bio-MEMS. In this study, we measure the hydrodynamic interaction directly without using the Stokes–Einstein relation. Two different cases are studied: a colloidal sphere near a single flat wall and a colloidal sphere located at the midplane between two flat walls. The colloidal hydrodynamics is measured as a function of the distance between the particle and the walls, and is compared with the theoretical results from well-defined hydrodynamics approximations.”

Additional Reading on Predominant Topics:

Optical Tweezers : Optical Tweezers, an Introduction