Article Index


This page lists all of the abstracts for the Spring 2016 colloquium series. For dates and speakers, see Colloquium.

"Spinning, Poynting, Translating: Shining Light on a TIRF Field in Order to Visualize HIV Assembly", Monday, February 1, 1:00pm, MH 606


Daniel Johnson, Rockefeller University

ABSTRACT: Total Internal Reflection Fluorescence (TIRF) Microscopy is an illumination technique in which fluorophores near a microscope cover glass (within ~100 nm) are excited, while those further away from the cover glass are not. This selective illumination typically reduces noise compared to traditional microscopy methods, thus making it easier to study single biomolecule complexes, such as individual proteins, nucleic acids and viruses. In addition, TIRF illumination has a unique polarization geometry enabling excitation of fluorophores aligned perpendicular to the cover glass surface, which is particularly useful for studying cell membranes. Here a novel TIRF illuminator will be described which enables visualization of structural changes in HIV particles throughout assembly in living cells, and observation of viral particle scission from the cell membrane following formation. In addition, the recruitment timing (hijacking) of cellular factors necessary for virus scission will be presented. Quantifying these processes provides insight into how HIV forms and leaves a cell, leading to the eventual invasion of another host. Interrupting this process may be an important factor in reducing the spread of HIV.

"Biophysical Interactions with Nanomaterials", Wednesday, February 3, 1:00pm, MH 606


Ran Chen, Kansas State University

ABSTRACT: Nanoscale materials have become widely adopted in various biomedically or environmentally relevant applications. In order to stimulate and facilitate these applications, there is an urgent need for a better understanding of the biophysical interactions of these materials with biological systems, especially on the cellular and molecular level. In this seminar, I will first introduce a series of comparative investigations on the cellular interactions of nanomaterials with animal and plant cells, and with subcellular structures like plasma membrane, and subsequent impact on the membrane structure. Then I will discuss about molecular level interaction of a few types of commonly used nanomaterials with biological macromolecules like proteins; I will show these interactions are determined by nanomaterial surface features and their binding with protein amino acid residues. Such binding shows impact on both the protein secondary structures and the nanomaterials surface physical or chemical properties, and subsequently change their interactions with other subcellular structures. Lastly I will introduce a modeling framework to systematically study the physical forces involved in biomolecule-nanosurface interactions by statistically analyzing massive experimentally obtained binding data, and the application of this framework toward molecular binding prediction and nanomaterial characterization based on their surface physical/chemical properties.

"Active mechanics keeps our cells alive.", Friday, February 5, 2:00pm, MH 606


Wylie Ahmed, Institut Curie (France)

ABSTRACT: Unlike traditional materials, living cells actively generate forces at the molecular scale that change their overall structure and mechanical properties. This nonequilibrium activity is essential for cellular function, and drives processes such as division, migration, and organization. In the first part of this talk, I will discuss how cells throughout the body (e.g. muscle, heart, tissue, and brain) must act as active mechanical systems to keep us alive. In the second part, I will discuss recent advances that allow quantification of nonequilibrium activity in living cells that provide insight on the molecular-scale driving forces. An understanding of active mechanics in living cells will uncover the basic physical principles driving biological processes and inspire new advances in nonequilibrium physics and materials science.

"Dark Sunshine", Friday, April 22, 12:00pm, MH 606


Flip Tandeo, University of California Irvine

ABSTRACT: The particle identity of dark matter is one of the most pressing open questions in high energy physics. In this talk, we review recent theoretical and experimental progress in the search for dark matter and the existence of dark forces. We highlight a particular class of searches based on dark matter collecting in the Earth or Sun that subsequently annihilates into dark force particles that are the analog of the ordinary photon. The observation of this "dark sunshine" or "dark earthshine" would be a smoking-gun signature for dark matter that would confirm a set of theories that have become particularly interesting from a range of recent experimental hints for new physics.

"Observation of gravitational waves from merging black holes", Friday, April 29, 12:00pm, MH 606


Geoffrey Lovelace, California State University Fullerton

ABSTRACT: On September 14, 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) made the first observation of gravitational waves passing through Earth. This gravitational-wave signal (named GW150914) originated from a pair of merging black holes over a billion light years away. In this talk, I will discuss this observation, the methods that made it possible, and implications for the dawning age of gravitational-wave astronomy. I will also highlight contributions from student and faculty researchers in CSUF’s Gravitational-Wave Physics and Astronomy Center, including a comparison of the LIGO observation with supercomputer calculations of the merging black holes and the gravitational waves they emitted.