This thesis focus on the analysis of spin-lattice NMRD relaxation profilesmeasured in various complex systems such as proteins, zeolites and ionicliquids. Proton, deuterium and fluoride T1-NMRD relaxation profiles wereobtained from a fast-field cycling (FFC) instrument. It is found that alsopossible to obtain NMRD profiles from the molecular dynamics (MD)simulation trajectories. NMRD Profiles were analyzed by using differentrelaxation models, such as the Solomon-Bloembergen-Morgan (SBM) theoryand the Stochastic Liouville (SL) theory. Paper I described the hydration of protein PrxV obtained from a MDsimulation, and compared with the picture emerges from an analysis byusing a generally accepted relaxation model [appendix C]. The result showsthat the information from NMRD analysis is an averaged picture of watermolecules with similar relaxation times; and the MD simulations containsinformation of all types of interested water molecules with differentresidence times. In paper II NMRD profiles have been used to characterize the hydration ofthe oxygen-evolving complex in state S1 of photosystem II. NMRDexperiments were performed on both intact protein samples and Mndepletedsamples, and characteristic dispersion difference were foundbetween 0.03 MHz to 1 MHz; approximately. Both the SBM theory and theSL theory have been used to explain this dispersion difference, and it isfound that this is due to a paramagnetic enhancement of 1-2 water moleculesnearby ~10 Å from the spin center of the Mn4CaO5 cluster. The result showsthe reorientation of the molecular cluster is in μs time interval. Whencompare these two theories, the SL theory presented a better interpretationbecause parameters obtained from the SBM theory shows they didn’t fulfilthe presupposed perturbation criterion (the Kubo term). Paper III deals with the water dynamics in the restricted/confined spaces inthe zeolite samples (H-ZSM-5 and NH4-ZSM-5) and obtained by proton anddeuterium spin-lattice NMRD profiles. The results show that the spin-latticeNMRD can be used to characterize various zeolites. The temperature has aweak effect on the relaxation rate R1, but the change of different counter ionsmay change the hydration and the translational diffusion pores and givedifferent R1. Proton and fluoride NMRD profiles and MD simulations were both used tostudy the dynamics of BMIM[PF6] in paper IV. Results indicate the reorientation of the molecules are in the ns time regime, and the effectivecorrelation time obtained from 1H and 19F are the same. From the MDsimulation it is found the reorientation of [PF6]- ions is much faster (in ps)compare with BMIM+ ion which moves in the ns time range. With previous results, the FFC NMRD profiles are indeed very informativetools to study the molecular dynamics of complex systems. The MDsimulation can be used as a complementary method to obtain detailedinformation. By combine these two methods, it provide a more colorfulpicture in the study of protein hydration and liquid molecular dynamics.

To optimize contrast agent in MRI scan region, e.g. to enhance paramagnetic relaxation in the MRI scan fields(0.1T-3T), one possible way is to slow down the tumbling of the paramagnetic complex. The effect of slowing down the reorientational motion of the complex to increase relaxivity is obvious and this strategy has already been employed in producing MRI contrast agent that can bind to specific proteins. An example is MS-325 binds to human serum albumin(HSA). The slow down effects on the ligands around paramagnetic ion, and on the zero field splitting(ZFS) interaction are under studies and the physics behind is still not clear. In this thesis, a generalized Solomon-Bloembergen-Morgan(GSBM) theory together with stochastic Liouville approach(SLA), is applied to investigate the mechanism behind the slow down effects. Two gadolinium complexes, MS-325+HSA and Gd(H2O)83++glycerol are studied by means of NMRD and ESR experiments. GSBM is a second order perturbation theory with closed analytical form. The computation based on this theory is fast, but it has its limitation and in the case of Gd(S=7/2) the ZFS strength times its correlation time(Δt.τƒ) should be less than 0.1. In comparison, the SLA is an "exact" theory that can evaluate the validity of GSBM calculation. However, the calculation in SLA is time consuming due to the large matrix it constructed. The major model used in GSBM is a two dynamic model, characterized by transient ZFS Δt and static ZFS Δs and their corresponding correlation time τƒ and τR, while in SLA the model is only described by Δt and τƒ. A combined NMRD and ESR analysis is used to understand the details of ZFS interaction. Both models can reproduce experimental NMRD profiles and model parameters are similar; for ESR linewidths the model parameters are quite different. The fitting results indicate the NMRD profiles are less sensitive to the detail expression of ZFS correlation function. In order to interpret both NMRD and ESR experiments with identical parameters, a more complex ZFS interaction model should be developed.

<p>To optimize contrast agent in MRI scan region, e.g. to enhance paramagnetic relaxation in the MRI scan fields(0.1T-3T), one possible way is to slow down the tumbling of the paramagnetic complex. The effect of slowing down the reorientational motion of the complex to increase relaxivity is obvious and this strategy has already been employed in producing MRI contrast agent that can bind to specific proteins. An example is MS-325 binds to human serum albumin(HSA). The slow down effects on the ligands around paramagnetic ion, and on the zero field splitting(ZFS) interaction are under studies and the physics behind is still not clear. In this thesis, a generalized Solomon-Bloembergen-Morgan(GSBM) theory together with stochastic Liouville approach(SLA), is applied to investigate the mechanism behind the slow down effects. Two gadolinium complexes, MS-325+HSA and Gd(H₂O)₈³⁺+glycerol are studied by means of NMRD and ESR experiments.</p><p>GSBM is a second order perturbation theory with closed analytical form. The computation based on this theory is fast, but it has its limitation and in the case of Gd(S=7/2) the ZFS strength times its correlation time(Δ<i>t</i>.<i>τ</i>_ƒ) should be less than 0.1. In comparison, the SLA is an "exact" theory that can evaluate the validity of GSBM calculation. However, the calculation in SLA is time consuming due to the large matrix it constructed. The major model used in GSBM is a two dynamic model, characterized by transient ZFS Δ<i>t</i> and static ZFS Δ<i>s</i> and their corresponding correlation time <i>τ</i>_ƒ and <i>τR</i>, while in SLA the model is only described by Δ<i>t</i> and <i>τ</i>_ƒ. A combined NMRD and ESR analysis is used to understand the details of ZFS interaction. Both models can reproduce experimental NMRD profiles and model parameters are similar; for ESR linewidths the model parameters are quite different. The fitting results indicate the NMRD profiles are less sensitive to the detail expression of ZFS correlation function. In order to interpret both NMRD and ESR experiments with identical parameters, a more complex ZFS interaction model should be developed.</p>

The thesis is focused on the synthesis and characterization of novel Mn2+ complexes as alternative to Gd3+ chelates which are wide-spread contrast agents in Magnetic Resonance Imaging (MRI). In the perspective to find suitable chelators of Mn2+ , three groups of pentadentate ligands with different size of macrocylic cavity, different donor atoms and number of pendant arms containing various functional groups have been investigated. Coordination numbers of 6 or 7 were found in the crystal structure of the Mn2+ complexes enabling binding of one or two water molecules in the first coordination sphere. The direct water coordination causes a decrease in the complex stability and thus, the thermodynamic stability of investigated chelates is lower than that of polyaminocarboxylate complexes and their dissociation is very fast in comparison to [Mn(nota)] and [Mn(dota)]2- . The studied Mn2+ complexes do not undergo oxidation in air except for complexes with 12-membered ligands which are oxidized to Mn3+ species. The proton relaxivities of the bishydrated complexes are two times higher than those for monohydrated complexes and are comparable to those of commercial contrast agents based on Gd3+ complexes. Variable-temperature 17 O NMR data revealed that the water exchange varies from slow to intermediate or...

Nous avons proposé des techniques de RMN à une et deux dimensions pour mesurer quantitativement les saturations et dynamiques de différents mélanges de saumure/huile brute/filtrat de boue confinés dans des roches pétrolières. La plupart de ces techniques peuvent être utilisées dans les puits. Les échantillons de roches ont été caractérisés par les techniques standards de la pétrologie. La résonance paramagnétique électronique (RPE) a mis en évidence les sources de relaxation composées d'ions métalliques paramagnétiques de vanadyl (VO2+) et de radicaux libres stables dans des huiles brutes avec et sans asphaltène. La micro-chromatographie en exclusion de tailles couplée à la détection par spectroscopie de masse en haute résolution a démontré le piégeage de ces ions métalliques dans des composés de type " métallo-porphyrine " (MP) inclus dans les nanoagrégats d'asphaltène. Ces deux dernières techniques ont montré qu'environ 2/3 des ions VO2+ sont inclus dans les parties polaires de l'asphaltène tandis que 1/3 sont libres en solution. L'utilisation jointe des chromatographies en phase gazeuse (GC) et par perméation de gel ou d'exclusion stérique (GPC) a permis d'étendre considérablement l'étendue spatiale des distributions de longueurs de chaînes des hydrocarbures. Les distributions des temps de relaxation transverses et longitudinaux ont la même allure que celle obtenues par GC et GPC. Ce qui prouve que la dynamique des hydrocarbures est fortement corrélée à la longueur des chaînes. La partie centrale de notre étude a consisté en la proposition de nouvelles séquences de RMN à deux dimensions (D-T2) corrélant les distributions des coefficients de diffusion D et les temps de relaxation transverses T2. Nous avons appliqué ces séquences (D-T2) pour suivre continument les saturations progressives de fluides pétroliers confinés dans des grès poreux en conditions monophasique, diphasique et triphasique à température et pression variables. On a pu ainsi suivre continument, pour la première fois, les saturations et les diffusions de ces différents fluides au cours d'expériences d'imbibition-drainage dans des grès pétroliers. Finalement, on a confirmé les comportements anormaux D∝√T2 pour les T2 courts (longues chaînes d'hydrocarbures) dans le cas des huiles brutes avec asphaltène. On a aussi observé un comportement D≈Cte pour les T2 longs (courtes chaînes d'hydrocarbures). Un scaling non-linéaire T2->√T2 a montré que c'est au niveau de la dynamique moléculaire (de rotation et de translation) des hydrocarbures de longues chaînes moléculaires que résident les principaux effets de l'asphaltène. Le comportement nouveau D≈Cte a pu être expliqué en termes d'une affinité dynamique transitoire entre les petits hydrocarbures et les nanoagrégats d'asphaltène. Ce qui est compatible avec les dépendances bilogarithmiques des variations de la vitesse de relaxation longitudinale moyenne avec la fréquence de Larmor que nous avons observées dans le cas des huiles brutes avec asphaltène.