The atomic resolution structure of a low populated and transiently formed on-pathway folding intermediate of the FF domain from human HYPA/FBP11 has recently been reported[1]. The structure was determined on the basis of backbone chemical shift and bond vector orientation restraints measured on the ‘invisible’ intermediate state using relaxation dispersion nuclear magnetic resonance (NMR) spectroscopy that were subsequently input into the data-base structure determination program CS-Rosetta. This thesis focuses on the cross-validation of the structure so produced. We present here the solution NMR structure of a mimic of the folding intermediate that is highly populated in solution, obtained from the wild-type domain by protein mutagenesis. The ensemble of structures generated of the mimic are within 2Å of the relaxation dispersion/CS-Rosetta structures of the intermediate, with the non-native interactions in the intermediate also observed in the mimic. The results presented in this thesis strongly confirm the structure of the FF domain folding intermediate, in particular, and validate the use of relaxation dispersion derived restraints in structural studies of invisible excited states, in general.

The atomic resolution structure of a low populated and transiently formed on-pathway folding intermediate of the FF domain from human HYPA/FBP11 has recently been reported[1]. The structure was determined on the basis of backbone chemical shift and bond vector orientation restraints measured on the ‘invisible’ intermediate state using relaxation dispersion nuclear magnetic resonance (NMR) spectroscopy that were subsequently input into the data-base structure determination program CS-Rosetta. This thesis focuses on the cross-validation of the structure so produced. We present here the solution NMR structure of a mimic of the folding intermediate that is highly populated in solution, obtained from the wild-type domain by protein mutagenesis. The ensemble of structures generated of the mimic are within 2Å of the relaxation dispersion/CS-Rosetta structures of the intermediate, with the non-native interactions in the intermediate also observed in the mimic. The results presented in this thesis strongly confirm the structure of the FF domain folding intermediate, in particular, and validate the use of relaxation dispersion derived restraints in structural studies of invisible excited states, in general.

No description available.

Ce travail se place dans le contexte des recherches sur les mémoires quantiques pour la lumière. L’information quantique est stockée dans un état de superposition atomique, dont la durée de vie détermine le temps maximum de stockage.On s’intéresse particulièrement aux matériaux capables de capturer la lumière par excitation résonnante d’une raie d’absorption, puis de conserver l’information quantique dans un état de superposition du fondamental électronique.Dans Tm3+:YAG, l’information est enregistrée dans un état de spin nucléaire. Cependant le champ magnétique qui lève la dégénérescence nucléaire entraîne les différents spins à des vitesses de précession différentes, ce qui tend à détruire l’aimantation initiale, porteuse de l’information.Une étude quantique du cristal est réalisée lors du premier chapitre de ce manuscrit. Les trois chapitres suivants traitent des différents mécanismes conduisant au déphasage des spins nucléaires. On y trouvera différente analyses théoriques qui seront confirmées par un ensemble de résultats expérimentaux, ainsi qu’une description détaillée du dispositif expérimental. Enfin le dernier chapitre, prospectif, exploite les outils développés au cours de la thèse pour préserver les cohérences optiques. Il présente quelques résultats expérimentaux prometteurs sur l’allongement du temps de vie de ces cohérences optiques. / This work takes place in the context of research about quantum memories for light. The quantum information is stored in an atomic superposition state whose lifetime sets the maximum storage time. We are particularly interested in materials which are able to hold the light by resonant excitation of an absorption line, preserving the quantum information in a superposition state of the electronicfundamental.n Tm3+:YAG the information is stored in a nuclear spin state. However, the magnetic field which lifts the nuclear degeneracy generates different precession speeds of the spins. This destroys theinitial magnetization carrier of the information.In the first chapter of this thesis, a quantum analysis of the crystal is done. The following three chapters are devoted to different mechanisms to control the nuclear spins dephasing. There it ispossible to find different theoretical analysis which will be confirmed by a series of experimental measurements, including an extended description of the set-up. Finally, the last chapter presentsthe different techniques used to preserve the optical coherence. Promising experimental measurements are presented to extend the life time of the optical coherences.

Ce travail se place dans le contexte des recherches sur les mémoires quantiques pour la lumière. L'information quantique est stockée dans un état de superposition atomique, dont la durée de vie détermine le temps maximum de stockage.On s'intéresse particulièrement aux matériaux capables de capturer la lumière par excitation résonnante d'une raie d'absorption, puis de conserver l'information quantique dans un état de superposition du fondamental électronique.Dans Tm3+:YAG, l'information est enregistrée dans un état de spin nucléaire. Cependant le champ magnétique qui lève la dégénérescence nucléaire entraîne les différents spins à des vitesses de précession différentes, ce qui tend à détruire l'aimantation initiale, porteuse de l'information.Une étude quantique du cristal est réalisée lors du premier chapitre de ce manuscrit. Les trois chapitres suivants traitent des différents mécanismes conduisant au déphasage des spins nucléaires. On y trouvera différente analyses théoriques qui seront confirmées par un ensemble de résultats expérimentaux, ainsi qu'une description détaillée du dispositif expérimental. Enfin le dernier chapitre, prospectif, exploite les outils développés au cours de la thèse pour préserver les cohérences optiques. Il présente quelques résultats expérimentaux prometteurs sur l'allongement du temps de vie de ces cohérences optiques.

No description available.

<p>In this study, we concentrate on spin-1/2 systems. A series of tools using the Liouville space method have been developed for simulating of NMR of arbitrary pulse sequences.</p> <p>We have calculated one- and two-spin symbolically, and larger systems numerically of steady states. The one-spin calculations show how SSFP converges to continuous wave NMR. A general formula for two-spin systems has been derived for the creation of double-quantum signals as a function of irradiation strength, coupling constant, and chemical shift difference. The formalism is general and can be extended to more complex spin systems.</p> <p>Estimates of transverse relaxation, R₂, are affected by frequency offset and field inhomogeneity. We find that in the presence of expected B₀ inhomogeneity, off-resonance effects can be removed from R₂ measurements, when ||omega||<= 0.5 gamma\,B₁ in Hahn echo experiments, when ||omega||<=gamma\,B₁ in CPMG experiments with specific phase variations, by fitting exact solutions of the Bloch equations given in the Lagrange form.</p> <p>Approximate solutions of CPMG experiments show the specific phase variations can significantly smooth the dependence of measured intensities on frequency offset in the range of +/- 1/2 gamma\,B₁. The effective R₂ of CPMG experiments when using a phase variation scheme can be expressed as a second-order formula with respect to the ratio of offset to pi-pulse amplitude.</p> <p>Optimization problems using the exact or approximate solution of the Bloch equations are established for designing optimal broadband universal rotation (OBUR) pulses. OBUR pulses are independent of initial magnetization and can be applied to replace any pulse of the same flip angles in a pulse sequence. We demonstrate the process to exactly and efficiently calculate the first- and second-order derivatives with respect to pulses. Using these exact derivatives, a second-order optimization method is employed to design pulses. Experiments and simulations show that OBUR pulses can provide more uniform spectra in the designed offset range and come up with advantages in CPMG experiments.</p> / Doctor of Philosophy (PhD)