Physiology and Biophysics

Seminars

Sep
21
Thu
2017
PBIO Seminar Series: Andrei Smertenko @ HSB G-328
Sep 21 @ 9:30 am – 10:30 am

How plants conquer the space: the cell’s flying plates

Plant cytokinesis is orchestrated by a specialized structure, the phragmoplast. The phragmoplast first occurred in representatives of Charophyte algae and then became the main division apparatus in land plants.  Major cellular activities, including cytoskeletal dynamics, vesicle trafficking, membrane assembly, and cell wall biosynthesis, cooperate in the phragmoplast under the guidance of a complex signaling network. My research focuses on the self-organization processes that govern phragmoplast functions. I will give a general overview of plant cytokinesis, and present our recent data on the gamma-tubulin independent microtubule nucleation by the plant-specific protein MACERATOR and a conserved member of TPX2 protein family.

Andrei Smertenko, Ph.D.
Assistant Professor, Molecular Plant Sciences
Washington State University

host: Linda Wordeman

Oct
12
Thu
2017
PBIO Seminar Series: Liangyi Chen @ HSB G-328
Oct 12 @ 9:30 am – 10:30 am

High spatiotemporal resolution, three-dimension fluorescence imaging of biological samples in vivo

Dr. Liangyi Chen
Professor
Laboratory of Cell Secretion and Metabolism
Institute of Molecular Medicine,
Peking University, Beijing, China

Host: Bertil Hille

Abstract: I will give two stories. (i) One story describes unpublished ultrasensitive Hessian structured illumination microscopy that enables ultrafast and long-term super-resolution (SR) live-cell imaging. At a photon dose one order less than point-scanning microscopy, Hessian-SIM has achieved 88-nm and 188-Hz spatial-temporal resolution for live cells imaging and lasted thousands of images without artifacts. Operating at 1 Hz, Hessian-SIM enables hour-long, time-lapse SR imaging with mitigatable photobleaching, highlighting the possibility of achieving SR imaging with commonly used fluorophores for an unlimited period of time. (ii) The second story is our recent Nature Methods paper, our invention of the fast high-resolution miniature two-photon microscope for brain imaging in freely-behaving mice at the single-spine level. With a headpiece weighing 2.15 g and a new type of hollow-core photonic crystal
fiber to deliver 920-nm femtosecond laser pulses, the mini-microscope is capable of imaging commonly used biosensors at high spatiotemporal resolution (0.64 μm laterally and 3.35 μm axially, 40 Hz at 256 × 256 pixels). It compares favorably with benchtop two-photon microscopy and miniature wide-field fluorescence microscopy in the structural and functional imaging of Thy1-GFP- or GCaMP6f-labeled neurons. Further, we demonstrate its unique application and robustness with hour-long recording of neuronal activities down to the level of spines in mice experiencing vigorous body and head movements or engaging in social interaction.