National Repository of Grey Literature 33 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Dynamics of hydrogen bonded networks viewed by NMR spectroscopy
Dvořák, Petr ; Lang, Jan (advisor) ; Hanyková, Lenka (referee) ; Hritz, Jozef (referee)
Title: Dynamics of hydrogen bonded networks viewed by NMR spectroscopy Author: Petr Dvořák Department: Department of Low Temperature Physics Supervisor: doc. RNDr. Jan Lang, Ph.D., Department of Low Temperature Physics Abstract: This work describes especially experimental studies of dynamic processes in common polar solvents such as water and ethanol. The nuclear magnetic reso- nance (NMR) technique was used - primarily measurements of NMR relaxa- tions and measurements of self-diffusion coefficients using NMR. Three main topics were addressed. The first one deals with chemical exchange in mixtures of light and heavy water. Within this topic, a methodology for the preparation of ultra-pure samples was developed and a suitable method for suppressing radiation damping was proposed. Then the final samples were prepared, and the relaxation data were measured. Three models of chemical exchange were discussed. The second topic deals with correction of the Stokes-Einstein rela- tion so that it can also be used for determination hydrodynamic radii of small molecules and clusters. This correction was made by comparing the measured diffusion coefficients of the model molecules with the calculated diffusion coef- ficients using hydrodynamic simulations. The third topic deals with the relax- ivity of magnetic...
Metabolic profile of human brain in vivo in MR image and spectrum
Wagnerová, Dita ; Hájek, Milan (advisor) ; Lang, Jan (referee)
Magnetic resonance imaging and spectroscopic imaging have proven to be useful to monitor a metabolism in the human brain. The thesis is concerned to repeatability and reproducibility of spectroscopic data measured on 1.5T and 3T scanners and to the development of a new method enabling the separation of pathologic and healthy tissues in patients with brain tumor using the combination of MR spectroscopic and diffusion measurements. Evaluation of repeatability and reproducibility in white matter in the parieto-occipital region, in the hippocampus and in gray matter in the frontal lobe did not show significant differences in accuracy of measurements on 1.5T and 3T scanners, but showed a significant increase of signal-to-noise ratio on 3T As a part of the thesis a program KORELACE has been developed. The program enables the evaluation of spectroscopic and diffusion data on the "pixel-by-pixel" basis in individual subjects. The existence of a statistically significant inverse correlation between the concentrations of choline and the diffusion trace values has been proven in glioblastoma, but no significant correlation has been found in a healthy tissue in volunteers. The correlation can be used to characterize borders of brain tumors and to identify the healthy tissue. Simulations confirmed the influence of...
Dynamical Behaviour of Matrix Proteins from Mason-Pfizer Monkey Virus
Srb, Pavel ; Lang, Jan (advisor) ; Žídek, Lukáš (referee) ; Brus, Jiří (referee)
Title: Dynamical behaviour of matrix proteins from Mason-Pfizer Monkey Virus Author: Pavel Srb Department: Department of Low temperature physics Supervisor: doc. RNDr. Jan Lang, PhD. Abstract: We studied the oligomeric properties of betaretroviral nonmyristoylated ma- trix protein (MA) and its R55F mutant from the Mason-Pfizer monkey virus in solution by means of NMR spectroscopy. We have proven that the wild- type (WT) MA forms oligomers in solution. The final model of oligomeriza- tion of the WT MA was derived by concerted use of chemical shift mapping and diffusion-ordered spectroscopy measured on a set of protein samples with varying concentrations. We found that the Mason-Pfizer monkey virus WT MA exists in a monomer-dimer-trimer equilibrium in solution. Further a combination of NMR relaxation measurements and advanced analysis of molecular dynamics simulation trajectory provided an unprecedentedly de- tailed insight into internal mobility of matrix proteins of the Mason-Pfizer monkey virus. Strong evidence have been obtained that the oligomerization capacity of the wild-type matrix protein is closely related to the enhanced dynamics of several parts of its backbone on a nanosecond time scale. In- creased flexibility has been observed for two regions: the loop between he- lices α2 and α3 and the C-terminal...
Fast Dynamic Processes in Solution Studied by NMR
Šoltésová, Mária ; Lang, Jan (advisor) ; Mäler, Lena (referee) ; Batta, Gyula (referee)
Title: Fast Dynamic Processes in Solution Studied by NMR Spectroscopy Author: Mária Šoltésová Department: Department of low temperature physics, Charles University in Prague, and Department of Materials and Environmental Chemistry, Stockholm University Supervisor: doc. RNDr. Jan Lang, Ph.D., Department of low temperature physics, Charles University in Prague, and Prof. Jozef Kowalewski, Department of Materials and Environmental Chemistry, Stockholm University Abstract: Nuclear magnetic resonance (NMR) spectroscopy is capable to deliver a detailed information about the dynamics on molecular level in a wide range of time scales, especially if accompanied by suitably chosen theoretical tools. In this work, we employed a set of high-resolution NMR techniques to investigate dynamics processes in several weakly interacting molecular systems in solution. Van der Waals interactions play an important role in inclusion complexes of crypto- phane-C with chloroform or dichloromethane. The complex formation was thoroughly investigated by means of 1H and 13C NMR experiments along with the quantum- chemical density functional theory (DFT) calculations. We characterized kinetics, thermodynamics, as well as fine details of structural rearrangements of the complex formation. Internal dynamics of oligo- and...
Study of dynamical behaviour of H2O/D2O mixtures by NMR relaxation
Dvořák, Petr ; Lang, Jan (advisor) ; Hanyková, Lenka (referee)
Title: Study of dynamical behavior of H2O/D2O mixtures by NMR relaxation Author: Petr Dvořák Department: Department of Low Temperature Physics Supervisor: doc. RNDr. Jan Lang, Ph.D., Department of Low Temperature Physics Abstract: The subject of this diploma thesis is the chemical exchange in the mixture of light and heavy water, which was studied by methods of high resolution NMR. The first part of this thesis concerns methodology of sample preparation and methodology of measurement of relaxation times of mixture of light and heavy wa- ter. Experimental complications with elution of ions from tube glass, degassing of samples, radiation damping and sample heating by radio-frequency pulses were solved there. In the second part of this thesis the relaxation parameters of chemical exchange of selected sample at various temperatures were measured. Interpretations of experimental data (ionization, molecular clusters and isotopic equilibrium) was suggested. Keywords: NMR, relaxation, water, dynamics, chemical exchange
The study of spin-lattice and spin-spin NMR relaxation of 1H nuclei in water
Dvořák, Petr ; Englich, Jiří (advisor) ; Lang, Jan (referee)
The dependences of spin-lattice and spin-spin relaxation rates of 1H nuclei on the concentration of H2O in H2O-D2O mixtures were measured using experimental methods of high resolution NMR. Before this measurement, we investigated the influence of radiation damping, paramagnetic impurities and temperature upon measurement of relaxation rates, as well as methods of its reduction. We also measured the dependences of spin-lattice and spin-spin relaxation rates of 17O nuclei on the concentration of H2O in H2O-D2O mixtures. We discuss the results, aiming to verify the accurancy of prior interpretations and to assess the influence of chemical exchange.

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See also: similar author names
7 LANG, Jakub
7 Lang, Jakub
8 Lang, Jiří
2 Lang, Jozef
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