Petrophysical interpretation of 1H NMR relaxation responses from saturated rocks is complicated by paramagnetic species present in fluids. Oxygen dissolved in liquids is one common example. Dipolar interactions of oxygen’s unpaired electron spins with the magnetic moment of fluid nuclei provide a strong relaxation mechanism known as paramagnetic relaxation enhancement (PRE). As a result even low concentrations of dioxygen in its common triplet ground state significantly shorten longitudinal and transverse relaxation times of host fluids. This effect may be employed similarly to any standard tracer technique to study pore connectivity in porous media by detecting a change of oxygen concentration due to diffusion resolved in time and space. Since relaxation enhancement effect is likely stronger in non-wetting phase than in wetting one (where surface relaxation process dominates) this difference can be utilized to study wettability in immiscible multiphase systems. We use a relaxation time contrast between air-saturated and oxygen-free fluids to evaluate oxygen concentration change within two fluid phases saturating rock, to estimate time required to establish equilibrium concentration and to calculate a mutual diffusion coefficient of oxygen. A spatially- and time-resolved T2(z,t) experiment provides the time-dependent oxygen concentration change along the fully- and partially-saturated carbonate core plug exposed to air saturated oil at its inlet. We derive an effective mutual diffusion coefficient of oxygen and accordingly a tortuosity estimate as a function of position along the core and rock saturation. The spatially resolved oxygen diffusion-based tortuosity is compared to simulated conductivitybased tortuosity. The latter is calculated on a high-resolution micro-tomographic image of Mount Gambier limestone by solving the Laplace equation for conductivity.

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Chloroperoxidase (CPO) is the most versatile heme-containing enzyme that catalyzes a broad spectrum of reactions. The remarkable feature of this enzyme is the high regio- and enantio-selectivity exhibited in CPO-catalyzed oxidation reactions. The aim of this dissertation is to elucidate the structural basis for regio- and enantio-selective transformations and investigate the application of CPO in biodegradation of synthetic dyes. To unravel the mechanism of CPO-catalyzed regioselective oxidation of indole, the dissertation explored the structure of CPO-indole complex using paramagnetic relaxation and molecular modeling. The distances between the protons of indole and the heme iron revealed that the pyrrole ring of indole is oriented toward the heme with its 2-H pointing directly at the heme iron. This provides the first experimental and theoretical explanation for the "unexpected" regioselectivity of CPO-catalyzed indole oxidation. Furthermore, the residues including Leu 70, Phe 103, Ile 179, Val 182, Glu 183, and Phe 186 were found essential to the substrate binding to CPO. These results will serve as a lighthouse in guiding the design of CPO mutants with tailor-made activities for biotechnological applications. To understand the origin of the enantioselectivity of CPO-catalyzed oxidation reactions, the interactions of CPO with substrates such as 2-(methylthio)thiophene were investigated by nuclear magnetic resonance spectroscopy (NMR) and computational techniques. In particular, the enantioselectivity is partly explained by the binding orientation of substrates. In third facet of this dissertation, a green and efficient system for degradation of synthetic dyes was developed. Several commercial dyes such as orange G were tested in the CPO-H2O2-Cl- system, where degradation of these dyes was found very efficient. The presence of halide ions and acidic pH were found necessary to the decomposition of dyes. Significantly, the results revealed that this degradation of azo dyes involves a ferric hypochlorite intermediate of CPO (Fe-OCl), compound X.

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Calcineurin (CaN) plays an important role in T-cell activation, cardiac system development, and nervous system function. Previous studies have suggested that the regulatory domain (RD) of CaN binds Calmodulin (CaM) towards the N-terminal end of CaN. Calcium-loaded CaM activates the serine/threonine phosphatase activity of CaN by binding to the regulatory domain, although the mechanistic details of this interaction remain unclear. It is thought that CaM binding at the RD displaces the auto inhibitory domain (AID) from the active site of CaN, which activates phosphatase activity. In the absence of calcium-loaded CaM, the RD is at least partially disordered, and binding of CaM induces folding in the RD. Previous studies have shown that an ?-helical structure forms in the N-terminal half of the RD, but organization may occur in the C-terminal region as well. Here, we are presenting a model for the structural transition of the full length RD as it binds to CaM. Using nuclear magnetic resonance (NMR) spectroscopy, we have successfully assigned >85% of the 15N, 13C?, 13C? and HN chemical shifts of the unbound, regulatory domain of CaN. Secondary chemical shifts support a model where the RD is highly disordered. Our study of the CaM and CaN interaction supports the formation of a distal helix in the region between the AID and calmodulin-binding region. Heat capacity changes upon binding predict that 43 residues fold when CaM binds to CaN, consistent with the formation of this distal helix. Paramagnetic relaxation enhancement (PRE) studies of this interaction suggest a potential binding mode where the distal helix binds to CaM near residues I10-A11. Mutagenesis in the distal helix disrupts PREs, further supporting this hypothesis. Together, these data suggest that the interactions between CaM and the distal helix of CaN can be important in regulation of phosphatase activity.

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Cyclam (1,4,8,11-tetraazacyclotetradecane) derivatives are widely used for various purposes. In a medicine they are applied as ligands for radiometals applied as diagnostic or therapeutic agents against tumours, hypoxic brain tissues etc. In this thesis a new method for asymmetric cyclam derivati- ves preparation was developed. New cyclam derivatives with trifluoroethyl groups were prepared too. Paramagnetic metal complexes with these fluori- nated ligands can be used as contrast agents for 19 F-MRI. Keywords: Cyclam; Non-symmetric protection; Contrast agents; Trifluoroethylamines; Paramagnetic relaxation; 19 F-MRI.

<p>Oligosaccharides (carbohydrates) are a large class of biological molecules that are important as energy sources in the human body and have enormously varied biological functions. It is generally believed that biological activities of carbohydrates are related to their internal dynamics. The dynamic properties of some oligosaccharides in solution are studied in this thesis, by NMR relaxation. We have employed relaxation interference effects to investigate the conformational dynamics within oligosaccharides (in-tramolecular dynamics) and paramagnetic relaxation enhancement (PRE) as an experimental tool to study intermolecular dynamics. Most of the thesis concerns the dynamics of the methylene group in the two possibly mobile parts of the oligosaccharide: in the exocyclic hydroxymethyl moiety and in the glycosidic linkage position. To perform conformational dynamic studies, the more traditional auto-relaxation pa-rameters are combined with the relaxation interference terms or the cross-correlated relaxation rates (CCRRs). Some experimental schemes based on the initial-rate technique were developed for measuring CCRRs. The techniques are useful for labelled sugars as well as naturally abundant ones. Furthermore, various dynamical models ranging from the Lipari–Szabo approach to several more informative and complicated models such as the two-site jump model, restricted internal rotation and slowly relaxing local structure (SRLS), have been employed to interpret our experimental data. We have combined and com-pared different models; we have also developed a novel approach to existing models, by scaling dipolar coupling constants (DCC), to extract the dynamic behaviour and structural properties of the system. We found that the auto- and cross-correlated relaxation data analyses yield a consistent picture of the dynam-ics in all cases. Additionally, our investigations show that CCRRs are practically important for verifica-tion of certain dynamical and structural information that is difficult to be determined by other means. Moreover, the anisotropy of the carbon-13 chemical shielding tensor in the methylene group has been estimated, using the interference between dipole-dipole and chemical shift anisotropy.</p><p>This thesis also discusses using the PRE to investigate sugar dynamics relative to a paramagnetic MRI contrast agent in solution, which might be important in medicine. We have studied the intramolecu-lar dynamics of the trisaccharide raffinose in the presence of a gadolinium complex. We also investigated the effect of translational diffusion instead of rotational diffusion, which is normally more important in NMR. The paramagnetically enhanced spin–lattice relaxation rates of aqueous protons over a wide range of magnetic fields and of carbon-13 and protons of the sugar at high fields have been measured. The nuclear magnetic relaxation dispersion of water protons and the PREs of proton and carbon in the sugar are interpreted in terms of the model recently developed in our laboratory, allowing both outer- and inner-sphere PREs for water protons, but allowing only the outer sphere PRE for nuclei in the sugar. We found that the relative diffusion has a stronger effect on the PRE than the electron spin relaxation.</p>

Oligosaccharides (carbohydrates) are a large class of biological molecules that are important as energy sources in the human body and have enormously varied biological functions. It is generally believed that biological activities of carbohydrates are related to their internal dynamics. The dynamic properties of some oligosaccharides in solution are studied in this thesis, by NMR relaxation. We have employed relaxation interference effects to investigate the conformational dynamics within oligosaccharides (in-tramolecular dynamics) and paramagnetic relaxation enhancement (PRE) as an experimental tool to study intermolecular dynamics. Most of the thesis concerns the dynamics of the methylene group in the two possibly mobile parts of the oligosaccharide: in the exocyclic hydroxymethyl moiety and in the glycosidic linkage position. To perform conformational dynamic studies, the more traditional auto-relaxation pa-rameters are combined with the relaxation interference terms or the cross-correlated relaxation rates (CCRRs). Some experimental schemes based on the initial-rate technique were developed for measuring CCRRs. The techniques are useful for labelled sugars as well as naturally abundant ones. Furthermore, various dynamical models ranging from the Lipari–Szabo approach to several more informative and complicated models such as the two-site jump model, restricted internal rotation and slowly relaxing local structure (SRLS), have been employed to interpret our experimental data. We have combined and com-pared different models; we have also developed a novel approach to existing models, by scaling dipolar coupling constants (DCC), to extract the dynamic behaviour and structural properties of the system. We found that the auto- and cross-correlated relaxation data analyses yield a consistent picture of the dynam-ics in all cases. Additionally, our investigations show that CCRRs are practically important for verifica-tion of certain dynamical and structural information that is difficult to be determined by other means. Moreover, the anisotropy of the carbon-13 chemical shielding tensor in the methylene group has been estimated, using the interference between dipole-dipole and chemical shift anisotropy. This thesis also discusses using the PRE to investigate sugar dynamics relative to a paramagnetic MRI contrast agent in solution, which might be important in medicine. We have studied the intramolecu-lar dynamics of the trisaccharide raffinose in the presence of a gadolinium complex. We also investigated the effect of translational diffusion instead of rotational diffusion, which is normally more important in NMR. The paramagnetically enhanced spin–lattice relaxation rates of aqueous protons over a wide range of magnetic fields and of carbon-13 and protons of the sugar at high fields have been measured. The nuclear magnetic relaxation dispersion of water protons and the PREs of proton and carbon in the sugar are interpreted in terms of the model recently developed in our laboratory, allowing both outer- and inner-sphere PREs for water protons, but allowing only the outer sphere PRE for nuclei in the sugar. We found that the relative diffusion has a stronger effect on the PRE than the electron spin relaxation.