Default Location: 7th Floor Seminar Room (Keen Bldg) | |
Date | Description |
January | |
| 7 | First Day of Classes - Spring Semester 2008 |
| 14 | |
| 21 | Martin Luther King, Jr. Holiday |
| 28 | |
February | |
| 4 | |
| 11 | |
| 18 | Jens Feder, University of Oslo, Norway (Host: Per Rikvold) Structural Phase Transitions in Perovskites Abstract: Perovskites have the general structure ABO_3. Perovskites have many interesting properties, they may be ferroelectric, have dielectric anomalies, may be magnetic, and superconducting We discuss the structural phase transitions of SrTiO_3 , LaAlO_3 , and present experimental results on the three phase transitions in CsPbCl_3 . The theory of the structural phase transition introduces the concept of soft modes and order parameter. We present results of measurements of thermal expansion on CsPbCl_33, with a capacitance dilatometer with strain resolution of 10^-9, and temperature resolution of 2x10^-7. The II to III transition is shown to correspond to a bicritical point. About the speaker: Dr. Jens Feder is Professor of Physics at the University of Oslo, Norway. During his career, which spans more than four decades, he has done seminal work in nucleation theory, dynamics of phase transitions (which is the subject of today's seminar), dynamic light scattering, fractals (his book, ``Fractals", has been translated to Russian, Chinese, and Japanese), and applications of physics to the geosciences. He was the founding director of the University of Oslo's Centre of Excellence for the Physics of Geological Processes, an aspect of his work that he will discuss in the SCS Colloquium on Wednesday, February 27, at 3:30pm. |
| 25 | Robert Szoszkiewicz, Columbia University, New York, NY (Host: S. von Molnar) Single-molecule and local studies of mechanical (un)folding of proteins enzymatic catalysis and water structure at surfaces Abstract: Single-molecule and local studies of mechanical (un)folding of proteins, enzymatic catalysis, and water structure at solid surfaces. With the ability to watch one molecule at a time single-molecule techniques are unique in observing the processes, which otherwise are hidden in macroscopic observables or averaged out by ensemble measurements. In the force-clamp spectroscopy with atomic force microscopy (AFM) piconewtons of force can be applied along a precisely defined direction, and to a single molecule. First, I will show how to identify several distinct regimes associated with (un)folding of single protein molecules, and what kind of physical information can be extracted from there. Mechanical forces exerted on single protein molecules are inherently present in biological systems. Our muscles, cell transport, and cell motility (i.e., ability to move spontaneously) rely heavily on these forces. Next, I will show how we could have obtained the details of the energy landscape and conformational changes of the substrate-enzyme during an enzymatic catalysis, while using single molecule force-clamp spectroscopy with a particular choice of native enzyme, and an engineered polyprotein. Finally, in a series of local AFM measurements we studied water molecules confined in sub-nanometer gaps. Water in sub-nanometer gaps defines physical properties of cell membranes, and permeation of ion channels inside each cell membrane. On both hydrophilic and hydrophobic surfaces, we observed the oscillatory solvation forces arising from the density fluctuations within confined water layers, and we obtained an approximate viscosity of each water layer. |
March | |
| 3 | |
| 10 | Spring Break and APS Meeting |
| 18 | Ming-Cheng Mark Cheng |
| 20 | Hongjun Liang, University of California, Santa Barbara (Host: Andre Striegel) Directed and Tunable Electrostatic Assembly of Membrane Proteins |
| 24 | Hedi Mattoussi (Host: Geoff Strouse) |
| 27 | Dr. Jingjiao Guan, Ohio State University Micro and NanoDevices for Drug Delivery Abstract: Presence of a series of barriers for drug delivery inside human body necessitates the use of multi-scale and multifunctional devices to overcome the barriers. In this talk, I will introduce design, fabrication, and characterization of micrometer-scale polymeric devices prepared by soft lithography for oral drug delivery. However, a microdevice alone is not enough for overcoming all the barriers in many cases of drug delivery and nanodevices are needed in order to have a fully successful delivery. I will thus describe the production of gene-delivery nanodevices by microfluidics to achieve better controlled particle size, more uniform composition, and higher transfection efficiency. Finally I will introduce an ongoing effort of developing a novel nanoengineering approach to the production of nanodevices for gene delivery. |
| 31 | Dr. Kuan Wang, Laboratory of Muscle Biology, NIH/NIAMS (Host: S. von Molnar) Extreme Muscle Biology: Force Sensing and Signal Transduction Nanomechanics of intrinsically disordered elastic proteins Abstract: Dr. Wang describes the implementation and optimization of an integrated platform of nanomechanics of intrinsically disordered elastic proteins such as titin and nebulin. This platetform includes protein engineering of polyproteins with built-in force handles, conformational studies in solution and on surface, force microscopy and single molecule imaging by AFM and simulated molecular dynamics and other computational techniques in analyzing the structural transitions of force events during protein unfolding/unraveling. These studies indicate that titin’s elastic PEVK appears to act both as an analog force sensor and as a transducer that converts the force input directly into biochemical signals of the SH3 pathways. Nebulin’s elasticity suggested that the continued presence of compressive force exerted by stretched nebulin is a requirement for thin filament assembly, integrity and maintenance. The novel concept that the elasticity of intrinsically disordered protein domains is an essential biological function is being explored for transcription factors and other signaling proteins. |
April | |
| 7 | |
| 14 | Steve Sligar (Host: Ken Taylor ) |
| 21 | Final Exams Week |
September | |
| 15 | Chun-Min Lo, University of South FL |