61 |
Analysis of mobile residues of E. coli citrate synthase using nuclear magnetic resonance spectroscopyChoudhary, Kajal 08 January 2007 (has links)
E. coli Citrate Synthase (CS) is a large hexameric protein with a molecular weight of 280kDa and belonging to the type II class of citrate synthases. The crystal structure of E. coli CS in the T (inactive) state is known. The structure shows that the backbone atoms of 42 residues (1-5, 266-297 and 330-335) have temperature factors about 9 times greater than the average as compared to the rest of the molecule. Residues 266-297, also referred to as the “Mobile loop”, are particularly of interest since they form a part of the active site and any rearrangement in the mobile loop can provide useful information about the R(active) state of the protein. In this study, Nuclear Magnetic Resonance (NMR) Spectroscopy has been used to study the flexible regions of E. coli CS in solution. The flexible residues have been assigned based on the amino acid type by 15N-specific amino acid labeling, while the residue type has been assigned by site-directed mutagenesis. Changes in the dynamics of the flexible residues, in response to the substrate binding, have been studied using both NMR and Fluorescence Spectroscopy. Also a method to use Mass Spectrometry for accessing the isotopic incorporation in the samples prepared for NMR spectroscopy has been described. The initial hypothesis in this study was that only the mobile loop residues which show significant high B-factors will contribute to the NMR spectrum. However in the NMR spectrum, in addition to the mobile loop, some uncharacterized flexible regions were also observed. We also found that some of the residues show signs of slow conformational exchange resulting in multiple signals in the NMR spectrum. In addition we see that the environment of some flexible residues is changed in the presence of substrates, a few residues were immobilized, but most remained mobile. / February 2007
|
62 |
Characterization and Control in Large Hilbert spaces.Ryan, Colm January 2008 (has links)
Computational devices built on and exploiting quantum phenomena have the potential to revolutionize our understanding of computational complexity by being able to solve certain problems faster than the best known classical algorithms. Unfortunately, unlike the digital computers quantum information processing devices hope to replace, quantum information is fragile by nature and lacks the inherent robustness of digital logic. Indeed, for whatever we can do to control the evolution, nature can also do in some random and unknown fashion ruining the computation. This thesis explores the task of building the classical control architecture to control a large quantum system and how to go about characterizing the behaviour of the system to determine the level of control reached. Both these tasks appear to require an exponential amount of resources as the size of the system grows. The inability to efficiently control and characterize large scale quantum systems will certainly militate against their potential computational usefulness making these important problems to solve. The solutions presented in this thesis are all tested for their practical usefulness by implementing them in either liquid- or solid-state nuclear magnetic resonance.
|
63 |
Fungal Spore Sensor Design Using Magnetic Resonance Force Microscopy2013 May 1900 (has links)
This work explores some of the considerations for the design and operation of a fungal spore sensor using Magnetic Resonance Force Microscopy (MRFM). This work starts by introducing the physics, components and theory of operation which make MRFM a favourable method for detecting the presence of fungal spores, which have
physical dimensions in the range of a few microns to a few hundred microns.
MATLAB was used to simulate changes in the dipole magnetic force which acts
between a mold spore and a MEMS cantilever beam during a MRFM experiment. The dimensions, characteristics and response of the cantilever beam is estimated
using MATLAB and re ned with multiple simulations in COMSOL Multiphysics.
The results are two cantilever models, one made using silicon and the other silicon nitride, have approximate quality factors of 30, spring constants around 80 10^6 N/m and resonance frequencies close to 10 kHz.
This work also discusses the proposed manufacturing process and considerations for the MEMS cantilever structure and the additional components of the intended prototype sensor. A sequence of operation for the initial calibration and typical operation of the spore sensor is also included in this work. The fungal spore itself is adhered within the sensing range of the sensor by using an antibody selectively
chosen to bind with the targeted spore. This work concentrates on the detection of the Botryris cinerea fungal spore, however the results from this work can be easily expanded on to detect additional fungal spores by changing the monoclonal antibody used to target the other spore types
|
64 |
Characterization and Control in Large Hilbert spaces.Ryan, Colm January 2008 (has links)
Computational devices built on and exploiting quantum phenomena have the potential to revolutionize our understanding of computational complexity by being able to solve certain problems faster than the best known classical algorithms. Unfortunately, unlike the digital computers quantum information processing devices hope to replace, quantum information is fragile by nature and lacks the inherent robustness of digital logic. Indeed, for whatever we can do to control the evolution, nature can also do in some random and unknown fashion ruining the computation. This thesis explores the task of building the classical control architecture to control a large quantum system and how to go about characterizing the behaviour of the system to determine the level of control reached. Both these tasks appear to require an exponential amount of resources as the size of the system grows. The inability to efficiently control and characterize large scale quantum systems will certainly militate against their potential computational usefulness making these important problems to solve. The solutions presented in this thesis are all tested for their practical usefulness by implementing them in either liquid- or solid-state nuclear magnetic resonance.
|
65 |
Investigation of the States of Water in Proton Exchange Membrane Nafion 117 with Nuclear Magnetic Resonance Relaxation and ExchangeWu, Zhen 10 September 2012 (has links)
The clustered water and interfacial water in Nafion 117 membrane have been quantified by NMR deuterium and proton experiments. The oscillation of intensity profile in 2H CPMG sequence with large duration time is induced by the residual quadrupolar interaction in clustered water. While the intensity profile of 2H CPMG sequence at short duration time followed the rule of exponential decay which is the consequence of the profile-overlapping between clustered water with residual quadrupolar interaction and interfacial water with susceptibility effect.
The populations of clustered water and interfacial water in fully hydrated membrane are estimated by quadrupolar echo sequence. The population of former and latter is 70% and 30%,respectively. At an elevated temperature, water in cluster region can transport to the interfacial region and result in change of intensity for proton spectrum. The activation energy of translational diffusion of interfacial water is lower than that of clustered water due to the strong binding energy between sulfonate group and water molecule.
The rf-heating effect on the proton spectrum of clustered water also has been explored by 1H CPMG and rotating-frame-relaxation-dispersion experiments. The dielectric response to a time-dependent external electric field provides a source of heat which causes a drift in chemical shift and interfere with transverse relaxation .
|
66 |
A nuclear magnetic resonance probe of Fe-Al and Al20V2Eu intermetallicsChi, Ji 15 May 2009 (has links)
Al-rich Fe-Al systems (FeAl2, Fe2 Al5 and Fe4Al13) and Al20V2Eu have complicated
structures with quasicrystal-like features making these materials potentially of
interest for magnetic behavior. However, there is not much work on these materials.
To study the variety of magnetic properties, we use NMR, magnetic susceptibility,
specific heat and other methods in this work.
The microscopic electronic and magnetic properties of the Al-rich Fe-Al system
and Al20V2Eu have been studied via 27Al NMR at temperatures between 4 and 500 K.
The results of spin lattice relaxation rates reveal a pseudogap in Fe4Al13 and Fe2Al5
around the Fermi-level in the density of states. Besides, a square well gap with a width
of 2 meV and center at Fermi energy was detected by specific heat measurements in
Fe2Al5. Both Fe4 Al13 and Fe2Al5 are non-magnetic systems with dilute magnetic defects,
while FeAl2 is a concentrated local magnetic moment system. In Al20V2Eu, a
crossover was observed in NMR, magnetization and transport measurements. Above
40 K, Eu(2+) local magnetic moments dominate; below 40 K, a transition to a Kondo
regime is observed, where the Kondo effect leads to the reduction of localized moments
due to the formation of a spin-compensated Kondo cloud. With increasing
magnetic field, f electrons participate more and more in excitations near the Fermi
level and a heavy-Fermion state was observed through specific heat measurements at
high magnetic field.
|
67 |
Hydration of Amino Acids Investigated by NMR SpectroscopyWang, Hui-Chun 25 August 2003 (has links)
none
|
68 |
Structure and Dynamics of a Novel Cobra Cardiotoxin CTXn as Derived from Nuclear Magnetic Resonance SpectroscopyHwang, Li-Cheng 29 August 2003 (has links)
none
|
69 |
Multi-nuclear One and Two Dimensional Solid State NMR Studies of Bis(2-Methyl-8-Quinolinolato)-(2,6-Dimethylphenolate)AluminumLi, Kun-ta 09 February 2004 (has links)
Bis(2-methyl-8-quinolinolato)-(2,6-dimethylphenolate)aluminum is a newly synthesized material suitable for manufacturing organic light-emitting devices (OLED). NMR parameters such as chemical shift, dipolar and quadrupolar tensors are intimately related to the electronic and geometric structures which are important for understanding its physical and chemical properties. In this work, we report the solid state NMR studies of this material. By using two-field (corresponding to proton resonance frequencies of 200 MHz, 500 MHz , respectively) 1D 1H MAS, 27Al MAS, 1H/13C CP/MAS and 2D 13C nutation MAS techniques, the chemical shift tensors of 13C and quadrupolar coupling constant of 27Al have been obtained. The relationship between these values and the light-emitting properties of this material is discussed.
|
70 |
The Dynamics of Protein CTXn from NMR Relaxation StudiesFang, Ching-hsia 05 September 2004 (has links)
none
|
Page generated in 0.3256 seconds