The increase of calcium in the cell can induce cellular functions such as fertilization, cell division and cell communication. Calcium (Ca2+) carries out these processes through proteins called calcium sensors. An important calcium modulator is calmodulin. Calmodulin has four possible Ca2+ binding sites that have the characteristic helix-loop-helix (EF hand) motif. When the EF hands bind to Ca2+, methionine rich hydrophobic patches are exposed allowing for CaM to interact with target proteins. However, there are proteins that can interact with CaM at low levels of Ca2+ or in the absence of Ca2+. An enzyme that is activated by CaM is nitric oxide synthase (NOS), which converts L-arginine to L-citrulline and nitric oxide (•NO), where •NO is used to carry out important cellular functions. There are three isoforms of the enzyme; endothelial, neuronal and inducible NOS. The first two isoforms are activated by Ca2+-bound CaM when there is an influx of Ca2+ and are therefore Ca2+-dependent whereas inducible NOS (iNOS) is activated and binds tightly to CaM regardless of the Ca2+ concentration and is therefore Ca2+-independent. Of particular interest is the iNOS enzyme, since no three-dimensional structures of the reductase domain or the CaM-binding region have been solved. All three isoforms of NOS exist as homodimers, where each monomer consisting of a reductase domain and an oxygenase domain separated by a CaM-binding region. The reductase domain contains binding sites for NADPH and the flavins, FAD and FMN, which facilitate electron transfer from the NADPH to the catalytic heme in the oxygenase domain of the opposite monomer. The transfer of electrons from the FAD to the heme is carried out by the FMN domain which is proposed to swing between the two docking points since the distance between the two points is too large for electron transfer. This electron transfer point is under the control of CaM, which is essential for NOS activation. This dynamic process and the direct role of CaM have yet to be observed structurally. A method to monitor dynamics structurally is through the use of nuclear magnetic resonance (NMR) spectroscopy. Therefore as the first step to determine the NMR structure of the FMN domain with the CaM-binding region, the structure of the iNOS CaM-binding region bound to CaM will be determined. The structure will allow for further characterization and identification of important interactions between the iNOS CaM-binding region and CaM which contribute to the unique properties of iNOS.

The increase of calcium in the cell can induce cellular functions such as fertilization, cell division and cell communication. Calcium (Ca2+) carries out these processes through proteins called calcium sensors. An important calcium modulator is calmodulin. Calmodulin has four possible Ca2+ binding sites that have the characteristic helix-loop-helix (EF hand) motif. When the EF hands bind to Ca2+, methionine rich hydrophobic patches are exposed allowing for CaM to interact with target proteins. However, there are proteins that can interact with CaM at low levels of Ca2+ or in the absence of Ca2+. An enzyme that is activated by CaM is nitric oxide synthase (NOS), which converts L-arginine to L-citrulline and nitric oxide (•NO), where •NO is used to carry out important cellular functions. There are three isoforms of the enzyme; endothelial, neuronal and inducible NOS. The first two isoforms are activated by Ca2+-bound CaM when there is an influx of Ca2+ and are therefore Ca2+-dependent whereas inducible NOS (iNOS) is activated and binds tightly to CaM regardless of the Ca2+ concentration and is therefore Ca2+-independent. Of particular interest is the iNOS enzyme, since no three-dimensional structures of the reductase domain or the CaM-binding region have been solved. All three isoforms of NOS exist as homodimers, where each monomer consisting of a reductase domain and an oxygenase domain separated by a CaM-binding region. The reductase domain contains binding sites for NADPH and the flavins, FAD and FMN, which facilitate electron transfer from the NADPH to the catalytic heme in the oxygenase domain of the opposite monomer. The transfer of electrons from the FAD to the heme is carried out by the FMN domain which is proposed to swing between the two docking points since the distance between the two points is too large for electron transfer. This electron transfer point is under the control of CaM, which is essential for NOS activation. This dynamic process and the direct role of CaM have yet to be observed structurally. A method to monitor dynamics structurally is through the use of nuclear magnetic resonance (NMR) spectroscopy. Therefore as the first step to determine the NMR structure of the FMN domain with the CaM-binding region, the structure of the iNOS CaM-binding region bound to CaM will be determined. The structure will allow for further characterization and identification of important interactions between the iNOS CaM-binding region and CaM which contribute to the unique properties of iNOS.

The three-dimensional structure of a protein molecule is the key to understanding its biological and physiological properties. A major problem in bioinformatics is to efficiently determine the three-dimensional structures of query proteins. Protein NMR structure de- termination is one of the main experimental methods and is comprised of: (i) protein sample production and isotope labelling, (ii) collecting NMR spectra, and (iii) analysis of the spectra to produce the protein structure. In protein NMR, the three-dimensional struc- ture is determined by exploiting a set of distance restraints between spatially proximate atoms. Currently, no practical automated protein NMR method exists that is without human intervention. We first propose a complete automated protein NMR pipeline, which can efficiently be used to determine the structures of moderate sized proteins. Second, we propose a novel and efficient semidefinite programming-based (SDP) protein structure determination method. The proposed automated protein NMR pipeline consists of three modules: (i) an automated peak picking method, called PICKY, (ii) a backbone chemical shift assign- ment method, called IPASS, and (iii) a protein structure determination method, called FALCON-NMR. When tested on four real protein data sets, this pipeline can produce structures with reasonable accuracies, starting from NMR spectra. This general method can be applied to other macromolecule structure determination methods. For example, a promising application is RNA NMR-assisted secondary structure determination. In the second part of this thesis, due to the shortcomings of FALCON-NMR, we propose a novel SDP-based protein structure determination method from NMR data, called SPROS. Most of the existing prominent protein NMR structure determination methods are based on molecular dynamics coupled with a simulated annealing schedule. In these methods, an objective function representing the error between observed and given distance restraints is minimized; these objective functions are highly non-convex and difficult to optimize. Euclidean distance geometry methods based on SDP provide a natural formulation for realizing a three-dimensional structure from a set of given distance constraints. However, the complexity of the SDP solvers increases cubically with the input matrix size, i.e., the number of atoms in the protein, and the number of constraints. In fact, the complexity of SDP solvers is a major obstacle in their applicability to the protein NMR problem. To overcome these limitations, the SPROS method models the protein molecule as a set of intersecting two- and three-dimensional cliques. We adapt and extend a technique called semidefinite facial reduction for the SDP matrix size reduction, which makes the SDP problem size approximately one quarter of the original problem. The reduced problem is solved nearly one hundred times faster and is more robust against numerical problems. Reasonably accurate results were obtained when SPROS was applied to a set of 20 real protein data sets.

NMR spectroscopy is not only for protein structure determination, but also for drug screening and studies of dynamics and interactions. In both cases, one of the main bottleneck steps is backbone assignment. When a homologous structure is available, it can accelerate assignment. Such structure-based methods are the focus of this thesis. This thesis aims for fast and robust methods for NMR assignment problems; in particular, structure-based backbone assignment and chemical shift mapping. For speed, we identified situations where the number of 15N-labeled experiments for structure-based assignment can be reduced; in particular, when a homologous assignment or chemical shift mapping information is available. For robustness, we modeled and directly addressed the errors. Binary integer linear programming, a well-studied method in operations research, was used to model the problems and provide practically efficient solutions with optimality guarantees. Our approach improved on the most robust method for structure-based backbone assignment on 15N-labeled data by improving the accuracy by 10% on average on 9 proteins, and then by handling typing errors, which had previously been ignored. We show that such errors can have a large impact on the accuracy; decreasing the accuracy from 95% or greater to between 40% and 75%. On automatically picked peaks, which is much noisier than manually picked peaks, we achieved an accuracy of 97% on ubiquitin. In chemical shift mapping, the peak tracking is often done manually because the problem is inherently visual. We developed a computer vision approach for tracking the peak movements with average accuracy of over 95% on three proteins with less than 1.5 residues predicted per peak. One of the proteins tested is larger than any tested by existing automated methods, and it has more titration peak lists. We then combined peak tracking with backbone assignment to take into account contact information, which resulted in an average accuracy of 94% on one-to-one assignments for these three proteins. Finally, we applied peak tracking and backbone assignment to protein-ligand docking to illustrate the potential for fast 3D complex determination.

<p>Understanding the interconversion between the thermodynamically distinguishable states present in a protein folding pathway provides not only the kinetics and energetics of protein folding but also insights into the functional roles of these states in biological systems. The protein component of bacterial RNase P holoenzyme from Bacillus subtilis (P protein) was used as a model system to elucidate the general folding/unfolding of an intrinsically unstructured protein (IUP) both in the absence and presence of ligands.</p><p>P protein was previously characterized as an intrinsically unstructured protein, and it is predominantly unfolded in the absence of ligands. Addition of small anions can induce the protein to fold. Therefore, the folding and binding are tightly coupled. Trimethylamine-N oxide (TMAO), an osmolyte that stabilizes the unliganded folded form of the protein, enabled us to study the folding process of P protein in the absence of ligand. Transient stopped-flow kinetic time courses at various final TMAO concentrations showed multiphase kinetics. Equilibrium "cotitration" experiments were performed using both TMAO and urea to obtain a TMAO-urea titration surface of P protein. Both kinetic and equilibrium studies show evidence of an intermediate state in the P protein folding process. The intermediate state is significantly populated and the folding rate constants involved in the reaction are slow relative to similar size proteins. </p><p>NMR spectroscopy was used to characterize the structural properties of the folding intermediate of P protein. The results indicate that the N-terminal (residues 2-19) and C-terminal regions (residues 91-116, 118 is the last residue) are mostly unfolded. 1H-15N HSQC NMR spectra were collected at various pH values. The results suggest that His 22 may play a major role in the energetics of the equilibria between the unfolded, intermediate, and native states of P protein.</p><p>Ligand-induced folding kinetics were also investigated to elucidate the overall coupled folding and binding mechanism of P protein and the holoenzyme assembly process. Stopped flow fluorescence experiments were performed at various final ligand concentrations and the data were analyzed using a minimal complexity model that included three conformational states (unfolded, intermediate and folded) in each of three possible liganding states (0, 1 and 2 ligands). The kinetic and equilibrium model parameters that best fit the data were used to calculate the flux through each of the six possible folding/binding pathways. This novel flux-based analysis allows evaluation of the relative importance of pathways in which folding precedes binding or vice versa. The results indicate that the coupled folding and binding mechanism of P protein is strongly dependent on ligand concentration. This conclusion can be generalized to other protein systems for which ligand binding is coupled to conformational changes.</p> / Dissertation

The wicking properties of multi-ply paper samples with dissimilar plies were investigated. These materials exhibit wicking performance in excess of either of their individual plies. Samples were produced from a ply of softwood pulp and a ply of hardwood pulp of equal caliper and basis weight. The softwood sample possessed a larger average pore size, a fact verified via porometry. Samples of a single ply were also produced for comparison. The samples were tested using both upward and downward gravimetric wicking tests. There was no saturation gradient observed, however there was a variation in the degree of bulk expansion during wicking. Capillary pressure and permeability for the various sample types were determined from the results of these tests and compared. It is shown that the wicking performance of the two ply sample is comparable to that of a theoretical material with the capillary pressure of the hardwood ply but the permeability of the softwood ply. Wicking in two-ply samples was also observed in an NMR apparatus. This was used to determine that the hardwood ply leads during wicking, and observe the rate of saturation as well as bulk expansion. A third type of experiment tracked the transport of dyed water from one ply to the other, establishing the direction of fluid transport during wicking to be from the softwood ply to the hardwood ply. The theory is proposed, based on these results, that wicking in this type of material consists of a smaller pored leading ply that draws water from a more permeable larger pored material that acts as a moving reservoir.

This dissertation focuses on two connected areas: quantum computation and quantum control. Two proposals to construct a quantum computer, using nuclear magnetic resonance (NMR) and superconductivity, are introduced. We give details about the modeling, qubit realization, one and two qubit gates and measurement in the language that mathematicians can understand and fill gaps in the original literatures. Two experimental examples using liquid NMR are also presented. Then we proceed to investigate an example of quantum control, that of a magnetometer using quantum feedback. Previous research has shown that feedback makes the measurement robust to an unknown parameter, the number of atoms involved, with the assumption that the feedback is noise free. To evaluate the effect of the feedback noise, we extend the original model by an input noise term. We then compute the steady state performance of the Kalman filter for both the closed-loop and open-loop cases and retrieve the estimation error variances. The results are compared and criteria for evaluating the effects of input noise are obtained. Computations and simulations show that the level of input noise affects the measurement by changing the region where closed loop feedback is beneficial.

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Proefschrift--Amsterdam. / Summary in Dutch. Includes bibliographical references.

Thesis (Ph.D.)--Memorial University of Newfoundland, 2001. / Bibliography: leaves [143]-150.