TcSUH
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Bi-Weekly Seminar
Electric Field Driven Torque in Rotary Biological Motors
Date: Friday July 24, 2009
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
Rotary motors, including ATP synthase, V-type ATPases, and the bacterial flagellar motor, play crucial roles in living organisms. In humans and other eukaryotes, ATP synthase operates in the inner membranes of mitochondria to produce adenosine triphosphate (ATP), life’s chemical currency of energy. V-type ATPases utilize the energy of ATP hydrolysis to create electrochemical potential differences (usually of protons) across diverse biological membranes. I will describe our recently proposed electric field driven torque model of ion-driven rotary motors. The model predicts a scaling law relating torque to the number of ion-carrying subunits in the rotor, the number of stators, and the ion motive force across the membrane. When the FO complex of ATP synthase is coupled to F1, the model predicts a minimum proton motive force (pmf) needed to drive ATP production by F1. By contrast the model predicts a maximum pmf against which the V1 complex of a V-type ATPase can overcome the opposing torque by V0 to pump protons back across the membrane. We are also working to develop label-free electromagnetic sensors to detect activity and possible dysfunction of mitochondrial and other enzymes. Dysfunction of mitochondrial enzymes has been implicated in type-2 diabetes, cancer, heart disease, and neurodegenerative diseases, while dysfunction of V-type ATPases has been implicated in osteopetrosis, distal renal tubular acidosis, and many other diseases. Therefore, improved understanding of such enzymes is broadly significant to human health.
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Bi-Weekly Seminar
Modulation of Calmodulin Plasticity by the Effect of Macromolecular Crowding
by: Margaret S. Cheung
Date: Friday May 22, 2009
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
In vitro biochemical reactions are most often studied in dilute solution, a poor mimic of the intracellular space of eukaryotic cells which are crowded with mobile and immobile macromolecules. Such crowded conditions exert volume exclusion and other entropic forces that have the potential to impact chemical equilibria and reaction rates. In this article, we used the well characterized and ubiquitous molecule calmodulin (CaM) and a combination of theoretical and experimental approaches to address how crowding impacts CaM's conformational plasticity. CaM is a dumbbell shaped molecule that contains four EF hands (two in the N-lobe and two in the C-lobe) that each could bind Ca2+ leading to stabilization of certain substates that favor interactions with other target proteins. Using coarse-grained molecular simulations, we explored the distribution of CaM conformations in the presence of crowding agents. These predictions in which crowding effects enhances the population of compact structures were then confirmed in experimental measurements using fuorescence resonance energy transfer techniques of donor/acceptor labeled CaM under normal and crowded conditions. We further explored the folding energy landscape and examined the structural characteristics of CaM at free energy basins using protein reconstruction methods. We discovered that crowding stabilizes several different compact conformations, which refects the inherent plasticity in CaM's structure. From these results, we suggest that the EF hands in the C-lobe are fexible and can be thought of as a switch, while those in the N-lobe are stiff as analogous to a rheostat. New combinatorial signaling properties may arise from the product of the differential plasticity of the two distinct lobes of CaM in the presence of crowding. We discuss the implications of these results for modulating CaM's ability to bind Ca2+ and target proteins.
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Bi-Weekly Seminar
Electropolymerizable Dendrimer and Hybrid Nanomaterials
by: Prof. Rigoberto Advincula
Date: Friday May 08, 2009
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
In this talk, we describe the investigation of dendrimeric precursor and hybrid nanomaterials towards the formation of conjugated polymer nanoparticles, networks, nanopatterning, and nanobjects. Electropolymerizable precursor polymer materials have been widely reported by our group and have been used to modify electrode surfaces with the formation of conjugated polymer network films. Most of these materials are based on linear polymers and block/graft copolymers. Very few reports have been given on dendritic precursor materials utilized for their electrochemical activity. In this talk, we will describe several strategies in which we have synthesized dendritic precursor polymers. These materials have applications for conducting polymer-based energy transfer materials, nanoelectronics, and sensing.
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Bi-Weekly Seminar
Direct Probe of the Key Building Block of the Fe-based Superconductors with Scanning Tunneling Microscopy/Spectroscopy (STM/S)
by: Dr. Shuheng H. Pan
Date: Thursday April 23, 2009
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
The recently discovered superconductivity in iron (Fe)-based compounds is another exciting advancement in condensed matter physics since the discovery of high-Tc superconductivity in cuprates. Using a UHV Low Temperature Scanning Tunneling Microscope, we have been studying the structural and electronic properties of the parent and Co-doped BaFe2As2 compound. We find that, by low temperature in situ cleaving, we are able to expose the key building block - the Fe-As layer of this compound, where superconductivity is believed to occur. With STM/S, we directly probe this key building block with spatial resolution down to atomic scale. STM is a surface sensitive technique. Keeping this in mind, I will demonstrate how we use this high real-space resolution and surface sensitive technique to learn the structural and electronic properties within the bulk. I will also discuss our results on the density-of-states (DOS) evolution with doping, the scaling of the superconducting energy gap, and some electronic local effects that may be used to help determine the pairing symmetry.
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Bi-Weekly Seminar
Interface Engineered Nanostructural Metamaterials with Anomalous Physical Phenomena
Date: Tuesday April 14, 2009
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
Interface engineered material has attracted more and more attention in the multifunctional materials research and active device fabrication. It plays a key role to control the physical properties of advanced nanomaterials and results in the discovery of various new physical phenomena with excellent opportunity for developing new metamaterials for active devices and engineered nanosystems. We have focused on the systematic studies on the formations and the characterizations of various highly epitaxial oxide thin films and multilayered layered structures to understand the nature of interface induced anomalous physical phenomena. Recently, by optimizing the epitaxial conditions we have successfully controlled and systematically investigated the highly epitaxial ferroelectric thin films and highly ionic conductive oxide thin films and the multilayered nanostructures. We have observed strong anisotropic phenomena in highly epitaxial (Pb,Sr)TiO3 thin films, and observed various anomalous physical phenomena such as locked ferroelectric domain formation from the multilayered BaTiO3/SrTiO3 superlattices for memory capacitance device and active actuator applications, extremely high ionic conductivity in the multilayered YSZ/GCO structures solid state fuel cells, and many others. Also, a series of models were developed to understand these interface phenomena. Details will be presented in the talk.
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