Green Hall, Room 0120
Masters Degree candidate Oumeng Zhang will present "Measuring Molecular Orientation and Rotational Mobility
Using a Tri-spot Point Spread Function".
Abstract: Single molecules have become a powerful tool for biophysicists since they were first optically
detected 28 years ago. Understanding molecular orientation can not only improve the accuracy of singlemolecule
localization, but it can also provide insight into biochemical behaviors at the nanoscale. In this thesis,
I present a method to measure the molecular orientation and rotational mobility of single-molecule emitters by
designing and implementing a tri-spot point spread function. The point spread function is designed so that it is
capable of measuring all degrees of freedom related to molecular orientation and rotational mobility. Its design
is optimized by maximizing the theoretical limit of measurement precision. Two methods, basis inversion and
maximum likelihood, are used to estimate the molecular orientation and rotational mobility. The basis inversion
method was demonstrated experimentally with fluorescent beads. The maximum likelihood estimator
approaches the theoretical limit of accuracy and precision in simulations, and is used to measure experimentally
the orientation of single fluorescent molecules embedded in a polymer matrix.
Research Advisor: Matthew Lew