PHYSICS IN MACROMOLECULES

Author: EL FADEH MOHAMED CHAOUKI.
Year: 2003.
University: COMPLUTENSE DE MADRID [www.ucm.es].
Place of defense: FACULTAD DE CIENCIAS FҍSICAS.
Place of preparation: FACULTAD DE CIENCIAS FҍSICAS.

Summary: The anÃÂ ¡lisis combined data difracciÃÂ ³ n X-ray real time, using a source of radiaciÃÂ ³ n sincrotrÃÂ ³ n, and susceptibility diamagnÃÂ © tica has allowed discuss a number of fenÃÂ ³ less than reordenaciÃÂ ³ n molecular slowly taking place in poliÃÂ © steres aromÃÂ ¡ticos such as: PEKK, PET, PEEK and P (HB / HN). These fenÃÂ ³ least include: relajaciÃÂ charges of orientaciÃÂ ³ n metaestable in the state amorphous segments aromÃÂ ¡ticos, relajaciÃÂ charges of orientaciÃÂ ³ n molecular initial, both uniaxial as planar, in funciÃÂ ³ n of time and temperature, asÃÂ as orientaciÃÂ charges induced by presence of a field magnÃÂ © tico. The study of diamagnetismo is able to offer a informaciÃÂ charges detailed on the state of ordenaciÃÂ ³ n molecule of a system to travÃÂ © s of changes in the inter - interactions that take place in it. Moreover, using the same tÃÂ © cnicas have been studied changes nanoestructurales that occur during cristalizaciÃÂ charges in the state sÃÂ ³ lido and during transitions to the state nemÃÂ ¡tico and the state cast isotrÃÂ ³ peak of the series copolÃÂmeros rÃÂgidos, P (HB / HN), caracterÃÂsticas crystal lÃÂquidos polimÃÂ © rich. The main conclusions to be reached at this Doctoral Thesis are as follows: 1-It has developed a simple structural model that has allowed explain the results of susceptibility diamagnÃÂ © tica amorphous samples with varying provisions regarding the field magnÃÂ © tico . The relajaciÃÂ charges of orientaciÃÂ charges of molecular segments has been described segÃÂ seventh n ecuaciÃÂ charges of Kohlrausch-Williams-Watts (KWW) with a time of relajaciÃÂ ³ n ÃÂ º nico. It has been proposed alternatively a new descripciÃÂ charges from a nÃÂ eighth mere finite intervals of time speeds relajaciÃÂ ³ n variables. 2, has been able to determine the cinÃÂ © tica of cristalizaciÃÂ charges of different polÃÂmeros through magnÃÂ © policies. The results were compared with those obtained by mÃÂ © all mÃÂ ¡s traditional. 3-Both the process relajaciÃÂ charges of orientaciÃÂ ³ n molecular like orientaciÃÂ charges of molecular chains rÃÂgidas, have tambiÃÂ © n be described by equations of the type KWW. The construcciÃÂ ³ n Curves teachers has demonstrated the validity of the principle of superposiciÃÂ ³ n tiempo-temperaturas in such fenÃÂ ³ less tÃÂ © rmicamente stimulated. 4, has been discussing the possible influence that the presence of the field magnÃÂ © tico induces on the different processes. It has been demonstrated that after an initial isotropizaciÃÂ charges, the field is capable of provoking a reorientaciÃÂ charges in copoliÃÂ © ster P (HB / HN) 75/25 high temperature.

Author: Font Sadurní Josep.
Year: 2005.
University: GIRONA [www.udg.es].
Place of defense: Facultat de Ciències, Universitat de Girona.
Place of preparation: Facultat de Ciències, Universitat de Girona.

Summary: Using temperature and pressure as denaturants we have explored the contributions to stability of the hydrophobic core residues of RNase A with the positions most critical for stability being V54, V57, I106 and V108. It is also shown that the stability differences can be attributed to both hydrophobic interactions and packing density with an equivalent energetic magnitude. These results are consistent with an exquisite tight core packing and the existence of rearrangements in the protein interior even after drastic deleterious substitutions. The role of hydrophobic interactions established by the residues that belong to the main hydrophobic core of RNase A in its pressure-folding transition state, was investigated using the phi-value method. The folding kinetics was studied using pressure-jump techniques both in the pressurization and depressurization directions. The structure of the transition state of the hydrophobic core of RNase A, from the point of view of formed interactions, is a relatively, uniformly expanded form of the folded structure with a mean phi f -value of 0.43. This places it half way between the folded and unfolded states. On the other hand, for the variants, the average of beta p-values is 0.4, suggesting a transition state that is 40% native-like. Altogether the results suggest that the pressure-folding transition state of RNase A, looks like a collapsed globule with some secondary structure and a weakened hydrophobic core. Pressure-jump induced relaxation kinetics was used to explore the energy landscape of protein folding/unfolding of Y115W variant of RNase A. Whereas downward p-jumps resulted always in single exponential kinetics, the kinetics induced by upward p-jumps was biphasic in the low pressure range (below P1/2) and monophasic at higher pressures. At 50 °C, only one phase was observable. Analysis of the activation volume of the fast phase suggests a temperature dependent structural shift of the unfolding transition state. The latter appears to interact strongly with the hydration shell, as indicated by results in the presence of glycerol. The present report gives first detailed kinetic evidence of a temperature and pressure dependent complex protein folding energy landscape.

Author: ECHENIQUE ROBBA PABLO.
Year: 2006.
University: ZARAGOZA [www.unizar.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: This thesis is developed, first, a series of computational and analytical tools to simulate biological macromolecules and with an eye on the problem of protein folding. It introduces a statistical test (distance), which allows comparison of different energies physically significant potential in complex systems. Following is an outline of internal coordinates for general organic molecules (called SASMIC), which allows separate maximalmente movements "soft" in the "hard" and that facilitates the imposition of ligatures holónomas on the system. Finally, in paragraph tool, it shows a result of the mathematical coordinates of external factors in determining the metric tensor that appear to integrate moments in statistical mechanics models linked. These tools are used in two practical problems, as a system using the dipéptido model formil-L-alanina-amida: First, it evaluates the dependence conformacional the terms corrective to the surface potential energy from the determinants metric tensor above and finally, is a study of the efficiency of different "model chemistries" with quantum chemistry methods RHF and MP2 and bases Pople.