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Organic-inorganic nanostructured composites are nowadays integrated in the field of material science and technology. They are used as advanced materials directly or as precursors to novel composites with potential applications in optics, mechanics, energy, catalysis and medicine. Many properties of these complex materials depend on conformational rearrangements in their inherently dynamic organic parts. The focus of this thesis is on the study of the molecular mobility in ordered nanostructured composites and lyotropic mesophases and also on the development of relevant solid-state NMR methodologies. In this work, a number of new experimental approaches were proposed for dipolar NMR spectroscopy for characterizing molecular dynamics with atomic-level resolution in complex solids and liquids. A new acquisition scheme for two-dimensional dipolar spectroscopy has been developed in order to expand the spectral window in the indirect dimension while using limited radio-frequency power. Selective decoupling of spin-1 nuclei for sign-sensitive determination of the heteronuclear dipolar coupling has been described. A new dipolar recoupling technique for rotating samples has been developed to achieve high dipolar resolution in a wide range of dipolar coupling strength. The experimental techniques developed herein are capable of delivering detailed model-independent information on molecular motional parameters that can be directly compared in different composites and their bulk analogs. Solid-state NMR has been applied to study the local molecular dynamics of surfactant molecules in nanostructured organic-inorganic composites of different morphologies. On the basis of the experimental profiles of local order parameters, physical motional models for the confined surfactant molecules were put forward. In layered materials, a number of motional modes of surfactant molecules were observed depending on sample composition. These modes ranged from essentially immobilized rigid states to highly flexible and anisotropically tumbling states. In ordered hexagonal silica, highly dynamic conformationally disordered chains with restricted motion of the segments close to the head group have been found. The results presented in this thesis provide a step towards the comprehensive characterization of the molecular states and understanding the great variability of the molecular assemblies in advanced nanostructured organic−inorganic composite materials. / <p>QC 20150225</p>

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Conformational dynamics are important to the function of biological molecules. While many experimental techniques (e.g. X-ray crystallography and NMR spectroscopy) have been developed for providing the structure of functional conformations, it is exceptionally challenging to understand conformational dynamics from experimental characterization. Molecular dynamics (MD) simulations is a powerful tool for probing conformational dynamics. The timescale resolution of MD simulations enables people to investigate intermediate conformations and transition pathways in atomic detail. Recent advancements in computer hardware have increased the timescales accessible to MD simulations. Meanwhile, more accurate and specific force fields have been developed to accurately model a variety biological system of different sizes. My graduate research has been focused on using MD simulations to study the conformational dynamics of proteins. Markov State Model (MSM) based approaches are extensively applied to investigate a variety of folding and/or binding mechanisms in atomic detail. Another focus of my work has been developing a Bayesian inference-based approach called BICePs to reconcile experimental measurements with simulation data to determine conformational ensembles and to validate force fields. / Chemistry

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