TcSUH
Bi-Weekly Seminar
Mechanisms and Detection of Biological Molecular Motors
Date: Friday October 31, 2008
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
Rotary motors, including ATP synthase and the bacterial flagellar motor, play critical roles in living organisms. ATP synthase produces ATP, life's chemical currency of energy, in all three domains of life - bacteria, archaea, and eukarya. In humans, ATP synthase operates in the inner membranes of mitochondria. I will describe our recently developed electric field driven torque model of ion-driven rotary motors. The model predicts a scaling law that relates 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 F0 complex of ATP synthase is coupled to F1, the model predicts a critical proton motive force below which ATP production drops to zero. In a human, such a drop in ATP would lead to unconsciousness and, eventually, death. We have also been measuring electromagnetic properties, such as impedance and harmonic responses, of live cells, mitochondria, and chloroplasts, in an effort to detect activity of active enzymes and changes in membrane potential. Dysfunction of mitochondrial enzymes has been implicated in type-2 diabetes, cancer, heart disease, Alzheimer's disease, and numerous specific mitochondrial disorders. Therefore, improved understanding of ATP synthase and other enzymes of mitochondrial respiratory chain is broadly significant to human health.
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Bi-Weekly Seminar
Electronic States and Dynamics at Semiconducting Polymer Heterojunction Interfaces
by: Prof. Eric Bittner
Date: Friday September 05, 2008
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
The optical-electronic properties of conjugated polymer-based electronic devices are acutely sensitive to the details of the intermolecular interactions and local environment. This is especially true at the interface between different semiconducting materials. In my talk I shall discuss our recent theoretical studies of OLEDS and solar cell materials based on polymer heterojunctions. Our theoretical approach combines modern quantum chemical methods based upon time-dependent density functional theory, projection operator techniques, and state of the art quantum dynamical methods for studying coupled electron/phonon systems. In my talk I shall discuss exciton breakup and recombination at interfaces as driven by phonons. I shall also talk about the possibility that interfacial triplet states may actually enhance the conversion efficiency of a heterojunction OLED device.
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Bi-Weekly Seminar
Quantum Measurement on Nano-Mechanical Resonators
Date: Friday July 11, 2008
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
Harmonic oscillator has been well described in both classical mechanics and quantum mechanics. Recent advances in nano-fabrication technology make nano-mechanical resonator a model macroscopic system for investigating quantum behaviors in experiment, e.g., zero-point motion fluctuation. Studying the measurement (interaction) on quantum states of such macroscopic systems may lead to the achievement of ultimate sensitivity for many physical variables limited by quantum interactions. I will describe recent progress in pursuing the position detection limit governed by Heisenberg uncertainty principle and quantum back-action effects, in nano-mechanical resonators coupled to mesoscopic detectors such as single-electron transistors. I will also talk on the potentials of carbon-nanotube based devices in pushing the mechanics into quantum regime.
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Bi-Weekly Seminar
Bioconjugation onto Silicon Surfaces
by: Chengzhi Cai
Date: Friday June 27, 2008
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
We have recently prepared robust monolayers on silicon or silicon carbide surfaces by surface hydrosilylation. We have demonstrated that these monolayers are the most protein-resistant and stable monolayers reported to date. We have also developed a method for nanopatterning on the above monolayers with 10 nm resolution, and introduced handles on the monolayers for bioconjugation. Meanwhile, we are developing "click" reaction based methods for efficient bioconjugation onto surfaces and nanoparticles. We have used the method to functionalize silicon and silicon carbide surfaces with carbohydrates. The research is relevant to the development of efficient silicon-neuron interfaces.
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Bi-Weekly Seminar
Mesoscopic Modeling of Biomolecules
by: Margaret S. Cheung
Date: Friday June 13, 2008
Time: 12:00 pm – 1:00 pm
Location: Houston Science Center – Building 593 — Room 102
Overview
Reconstruction algorithms from coarse-grained models to fine-grained (all-atomistic) models of biomolecules are essential in implementing multi-scale simulations. We developed an innovative algorithm for reconstruction that results in high precision all-atom structures (SCAAL). Our method is validated by the computation of structural differences in reconstructed conformations and Protein Data Bank structures for 67 proteins. Significant improvements are observed while we consider a special relevance between the side chain and the backbone of a protein into our modeling method.
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