Dissertations / Theses on the topic 'Solvation energies'
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Kurusu, Tamaki. "Computer simulation of free energies to predict cis/trans equilibria of prolyl peptides and solvation free energies of phenylalanyl peptides." Thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/45091.
Full textIn Part I, the free energy perturbation (FEP) method, using AMBER, was utilized to calculate the Gibbs free energy difference between cis and trans conformers of Ace-Tyr-Pro- NMe and Ace-Asn-Pro-NMe, from which the ratio of cis to trans conformers was obtained. Our simulation generated much lower %cis for both peptides as compared with experimental values and possible problems in our computational schemes are presented. However, our results were encouraging in that they predicted preference of trans conformers for both peptides and higher %cis for Ace-Tyr-Pro-NMe, compared to Ace-Asn-Pro-NMe, which agrees with experimental results.
Part II applied semi empirical (AMS0L) and microscopic simulation (POLARIS) methods to obtain the solvation free energies of a series of phenylalanyl peptides with various degrees of methylation on their backbone nitrogens. It was clearly predicted that as a peptide length increased, so solvation free energy decreased, indicating less favorable permeability through the cell membrane system, in agreement with data in the literature. AMSOL also showed that solvation free energy change upon methylation was variable depending on the position of the substituted backbone nitrogen, which disagrees with the literature. However, non-systematic solvation free energy change of small amines upon methylation was successfully predicted by AMSOL, in good accord with experimental data.
Master of Science
Cumberworth, Alexander Michael. "Implicit solvent models and free energies of solvation in the context of protein folding." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/52833.
Full textScience, Faculty of
Graduate
Pollard, Travis P. "Local Structure and Interfacial Potentials in Ion Solvation." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491562324303743.
Full textGebhardt, Julia [Verfasser], and Niels [Akademischer Betreuer] Hansen. "Biomolecular force fields probed by free energies of binding and solvation / Julia Gebhardt ; Betreuer: Niels Hansen." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2021. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-ds-116887.
Full textAttah, Isaac Kwame. "BINDING ENERGIES AND SOLVATION OF ORGANIC MOLECULAR IONS, REACTIONS OF TRANSITION METAL IONS WITH, AND PLASMA DISCHARGE IONIZATION OF MOLECULAR CLUSTERS." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/525.
Full textMoine, Edouard. "Estimation d’énergies de GIBBS de solvatation pour les modèles cinétiques d’auto-oxydation : développement d’une banque de données étendue et recherche d’équations d’état cubiques et SAFT adaptées à leur prédiction." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0295/document.
Full textLiquid phase oxidation of hydrocarbons (also called autoxidation) is central to a large number of processes in the petrochemical industry as it plays a key role in the conversion of petroleum feedstock into valuable organic chemicals. This phenomenon is also crucial in oxidation-stability studies of fuels and its derivatives (aging). These liquid-phase oxidation reactions entail radical mechanisms involving more than thousands of compounds and elementary reactions. Kinetic modelling of these kinds of reactions remains a significant challenge because it requires thermodynamic and kinetic parameters, which are not abundant in literature. The EXGAS software, developed at LRGP, is able to generate these kinds of models but only for oxidation reactions taking place in a gaseous phase. It is assumed that the nature of elementary reactions in the liquid and gaseous phases is the same. The unique need to transfer a kinetic mechanism from a gas phase to a liquid phase is to update kinetic rate constant values and equilibrium constant values (called thermokinetic constants) of mechanism reactions. Therefore, in the framework of this PhD thesis, a new method aimed at applying a correction term to thermokinetic constants of gaseous phases is proposed in order to obtain constants usable to describe liquid-phase mechanisms. This correction involves a quantity called partial molar solvation GIBBS energy. An analysis of the precise definition of this property led us to conclude that it can be simply expressed as a function of fugacity coefficients and liquid molar density. As a result, this property could also be expressed with respect to measurable thermodynamic quantities as activity coefficients or HENRY’s law constants. By combining all the experimental data related to these measurable properties that can be found in the literature, it was possible to develop a comprehensive databank of partial molar solvation GIBBS energies (called the CompSol database). This database was used to validate the use of the UMR-PRU equation of state to predict solvation quantities. Moreover, the bases of a new parameterization for SAFT-type equations of state were laid. It consists in estimating pure-component parameters of SAFT-like equation using a very simple, reproducible and transparent path for non-associating pure components. This equation was used to calculate partial molar GIBBS energy of solvation of pure and mixed solutes. Last, equations of state were combined with EXGAS software to model the oxidation of n-butane in the liquid phase
Opoku-Agyeman, Bernice. "Complexities in Nonadiabatic Dynamics of Small Molecular Anions." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503094708588515.
Full textJeanmairet, Guillaume. "Une théorie de la fonctionnelle de la densité moléculaire pour la solvatation dans l'eau." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://tel.archives-ouvertes.fr/tel-01067993.
Full textBasdevant, Nathalie. "Un Modèle de Solvatation Semi-Implicite pour la Simulation des Macromolécules Biologiques." Phd thesis, Université d'Evry-Val d'Essonne, 2003. http://tel.archives-ouvertes.fr/tel-00010619.
Full textShimizu, Karina. "Estudo do método de equalização da eletronegatividade no cálculo de energias livres de solvatação GBEEM-ELR." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/46/46132/tde-14092006-174816/.
Full textThe electronegativity equalization method (EEM), founded on density functional theory (DFT), has been combined to the generalized Born approximation (GB) for molecules, and called GBEEM (Dias et al., 2002). The permanent dipole moment in vacuum and condensed phase (dieletric constant ~ 80), and atomic charges distributions, have shown good agreement with SM5.4 solvation model based on CM1 charges at PM3 level (12 molecules, corresponding to 29 atomic charges). This result is interesting due the simplicity of GBEEM and its low computational cost. A new parameterization of the hardness and electronegativities was done with the aim to improve the atomic charges distribution on isolated molecules in comparison to CM1 model. The training set with 250 PM3/CM1 structures/charges of neutral molecules in 13 different organic functions was employed as target in the parameterization. A new optimization approach composed of Genetic and Simplex algorithms was used to fit parameters (Menegon et al., 2002). Good agreement between the models was found. The validation of parameterization and EEM was done using bifunctional molecules (tri-glucose and tetra-peptide) showing good agreement and robustness. However, analysis of permanent dipole moments of 250 molecules shown a serious caveat of EEM and GBEEM, beside the good agreement between EEM and CM1 charges. EEM has overestimated the dipole moments. Such result may be due to the truncated expansion in atomic charges and lacking of explicit treatment of exchange interaction. A new approximation was proposed constraining the charge transfer between groups within the molecule. This approximation corrected the caveat of EEM in the prediction of dipole moments in vacuum and condensed phase (Shimizu et al., 2004). Based on these results, a new solvation model was developed founded in GBEEM and Floris-Tomasi model. The parameterization was done with a training set of 62 neutral molecules (13 functional groups) and experimental hydration free energies as target. This new solvation model has produced a mean absolute deviation, MAD, of 0.71 kcal/mol comparing to experimental data.
Silva, Priscilla Leandro. "Solvatação em solventes puros e misturas binárias: fundamentos e aplicações." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/46/46135/tde-02112011-122800/.
Full textThis work is aimed at understanding solvation in pure solvents and binary mixtures and, the application of the information obtained in order to analyze the solvents effects on the synthesis of an ionic liquid, and on the dependence of the properties of cellulose acetate films, CA, on the degree of substitution of the ester. To understand salvation, was have used compounds (solvatchromic probes), whose UV-vis spectra are susceptible to the environment properties. In addition to these probes, were used more two tools: (i) Preferential solvation model; it was proposed by our research group and describes the composition of the probe solvation shell, considering the existence of an aggregate between water and organic solvent. (ii) Multi-parameter solvation free energy equations that correlate the solvent dependent properties with solvents properties and their mixtures. At first, we have studied pairs of probes that have similar pKa values and different lipophilicity in protic solvents. We have concluded that solvent acidity and dipolarity/polarizability are the most important properties. These conclusions are supported by theoretical calculations, that have shown the relationship between structural features of the probe and its susceptibility to environment properties. The same set of probes was used in order to study water - protic solvents mixtures. In this, we have applied the above cited solvation model successfully and rationalized the equilibrium constants of the exchange of species present (water, solvent and water -solvent) in the solvation shell with the properties of pure solvents and / or binary mixtures. These results revealed that the composition of solvation shell is controlled by the properties of solvents, in special, lipophilicity and basicity. The probes RB and WB were studied in mixtures of water with alcohols and with aprotic solvents. The intention was to broaden the applicability of the solvation model, for which, we needed to know the molar volume of the aggregate VSolv-W, and the dissociation constant, Kdissoc, of the same. Previously, these two quantities were obtained, simultaneously, by iteration of density data. We have used theoretical calculations in order to obtain VSolv-W and then use it as constant parameter (not adjustable one) in the calculation of Kdissoc. Comparison of the results showed that, in both approaches, the differences between Kdissoc values were minimal. Moreover, the order of Kdissoc has not changed. This observation is due to the fact that the simultaneous calculation of Kdissoc and VSolv-W was always based on a large number of density data (18) so that the interation did not converge to a false minimum; the level of theory used in the theoretic calculations was appropriate. Regarding applications, our results showed the importance of the choice of solvent to the synthesis of an ionic liquid. We have attempted to reproduce the properties of CA by the use of two models, ethanol-ethyl acetate and cellulose triacetate-cellulose. The data of the liquid mixture showed preferential solvation; were successfully treated by the same model applied to aqueous binary mixtures. The solid model reproduces the CA data qualitatively.
Blouet, Christelle. "Utilisation d'une méthode électrochimique pour la détermination simultanée de coefficients d'activité et d'énergies de transfert dans des solutions non-aqueuses d'électrolytes et dans des mélanges de solvants." Paris, ENMP, 2005. http://www.theses.fr/2005ENMP1321.
Full textThe representation of the thermodynamic properties of electrolytes solutions in mixed-solvent is a strong industrial stake. However the thermodynamics modelling of these systems presents specifics difficulties. In the present study, we carried out an electrochemical cell with ion selective electrodes in order to determine experimental measurements that could be used to improve the representation of non-aqueous and mixed-solvent electrolytes solutions. This method allows us to obtain not only experimental values of mean activity coefficient but also of the standard gibbs energy of transfer, a property necessary to express the mean activity coefficients in a reference state that does not depend on the mixture composition. The first measurements have been relative to solutions of naci and nabr in methanol and water-methanol mixtures. The new device was then used to determine the partition coefficient of naci between the two liquid phases produced by the water-n-butanol system
Giudice, Emmanuel. "Etude par dynamique moléculaire des aspects énergétiques et conformationnels des déformations de la double hélice d'ADN en fonction de sa séquence de bases." Paris 6, 2003. http://www.theses.fr/2003PA066139.
Full textNait, Saidi Chourouk. "Modélisation de la conversion thermique de carburants verts de type bio-huiles." Thesis, Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAE010.
Full textProduction of bio-oils through thermochemical biomass conversion is a promising process for biorefining. While gas phase kinetics of bio-oil conversion has been improving, its liquid phase reactivity is currently poorly understood. The aim work of my thesis is about the understanding of detailed kinetics mechanism of biomass thermochemical decomposition at low temperature range in the liquid phase. As mentionned by Basu (June 2010); Nakamura et al. (2007a,b); Kawamoto (2017) a liquid phase is observed during the initial stage of biomass pyrolysis. In this study, we will try to model the initial stage of biomass pyrolysis. To our knowledge, no modelling study of the rate of reactions in the liquid phase has been proposed for biomass pyrolysis. The investigation of liquid phase reactions of such complex systems requires a good knowledge of solvent effects. We compared the prediction capabilities of COSMO-SAC with those of the Abraham solvation model, by considering the COMPSOL database of Moine (2017) as the reference data. We then proposed a re-parametrization of these COSMO-SAC models that leads to much better predictions, and extended these models to CPCM cavities(Nait Saidi et al. (2020)). Predictive methods based on ab initio calculations can be very accurate for predicting gas phase thermochemical properties and are usually more versatile than group contribution methods. An extension of Paulechka and Kazakov (2017) ab initio prediction method of enthalpies of formation was proposed in this study (Mielczarek et al. (2019)) and used for biomass compounds. We then used Reaction Mechanism Generator (RMG) to investigate the possible reaction mechanism of different Tar surrogate compounds of biomass decomposition. The surrogate compounds that we chose are Creosol, guaiacol and methoxy vinylphenol to model the lignin. This work can be considered as an extension of the gas phase reaction mechanism of pyrolysis proposed by Ranzi(2017a,b) taking in consideration the primary tar recombination/polymerisation reaction that occur in the temperature range 100°C to 300°C.To model the kinetics of the key reaction, we investigated the transitional state using Gaussian 09 and ORCA. We then estimated the kinetics parameters using Transitional State Theory with Kisthelp tool (Canneauxet al. (2014)) and liquid phase kinetics approach based on the gas phase kinetics and solvation free energies correction (Jalan et al. July 2013)
Russier, Vincent. "Contribution à la description théorique de l'interface métal noble / solution électrolytique." Paris 6, 1986. https://hal.science/tel-04577395v1.
Full textTheoretical description of the interface between a noble metal and an electrolytic solution. The description of the solution-wall solid interface is described by the "civilized" model in which the molecules are hard spheres bearing a point dipole and the ions of charged hard spheres. Determination of the density profile of dipoles when they interact with the surface and the density profile of ions. For noble-vacuum metal interface, calculation of output work and surface energy. Use of a simple model to treat the surface and account for hybridization s/d
Silva, Carlos Eduardo Bistafa da. "Estudos teóricos do estado excitado de moléculas orgânicas em solvente." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-22102015-102635/.
Full textAbsorption and emission of electromagnetic radiation by molecules in the UV-Vis region yields information about the electronic excited states, being properties of great interest due its relation with biological process, as well as its possible applications in diagnostics and technology. These properties are sensible to the environment in which the molecules are, making natural the search for theoretical methods that describe these interactions. In this work, we have used the Sequential-Quantum Mechanics/Molecular Mechanics methodology to study the spectrum of absorption and emission of molecules of biological relevance, when in solution. Classical Monte Carlo simulations were carried out to construct an average solvent electrostatic configuration and used to represent the liquid in posterior quantum mechanics calculation of the properties, performed by using the multiconfigurational methods CASSCF and CASPT2. Special cares were taken to include the electronic polarization of the solute due the solvent. Our contribution is the adaptation of the Free Energy Gradient method to allow the determination of the solute excited states geometries in solution. The method was implemented in a computer program and successfully applied in the systems studied. The perspectives are now open to the calculation of conical intersection in solvent environment, enabling the study of nonradioactive decays in solvated systems.
Lima, Gilson Alberto Rosa. "Análise de solubilização micelar através do uso de parâmetros derivados de química quântica." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/46/46132/tde-02122015-124715/.
Full textOne of the most fundamental properties of aqueous micelar solutions is their ability to solubilize a wide variety of organic solutes with quite distinct polarities and degree of hydrophobicity. Recently Quina et al., studied the specific chemical interactions governing the solubilities of a wide range of solutes in micelles using linear solvation energy relationships (LSERs) based on empirical solute parameters developed by Abraham. This work reports an investigation of the solubilization of organic solutes in micelles based on the use of theoretical solute parameters derived from quantum chemical calculations Our results show that the experimental Ks values for solubilization of organic solutes in anionic detergents (micelles of SDS-sodium dodecyl sulfate and aggregate formed between SDS and PEG-poly(ethylene glycol)) can be reproduced using theoretical parameters. The resultant theoretical linear solvation energy relationships are chemically consistent with LSERs based on empirical solute parameters. In the case of cationic and nonionic detergents, the theoretical parameters used to describe hydrogen bonding fail because methods of calculating formal charges using the concept of Mulliken populational analysis cannot describe hydrogen bonding donor and acceptor character in an appropriate way. Possible strategies to solve the theoretical descriptor problem in the context of the linear free energy approximation are discussed.
Cunha, Antonio Rodrigues da. "Estudos teóricos de propriedades estruturais e eletrônicas da molécula emodina em solução." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-09042010-104047/.
Full textWe study the structural and electronic properties of the emodin (EM) in different solvents of experimental and theoretical the point of view. We started performing measurements of the UV-Vis absorption spectrum of the EM in solution (water, chloroform and methanol). Our main result is that the solvent causes little effect on shifts the bands. In the second part of this work, we performing quantum calculations of isolated EM and in the three solutions using density functional (B3LYP), a set of Pople basis function (6-31G*) and the polarizable continuum model (PCM). In this part, our result is that EM presents a rigid conformation unless the orientation of its 3 hydroxyls. The change in these hydroxyls orientation can form up to 2 intramolecular H-bonds (which stabilizes its geometry) and causes a decrease in the dipole moment from 5.5 to 1.7D (which destabilizes its interaction with water). In the third part of this work, we performing Monte Carlo and Molecular Dynamics simulations in solution. Our main result is that the intramolecular H-bonds are rarely broken, even in aqueous solution, and these give to EM a hydrophobic character. Additionally, using Thermodynamics Perturbation Theory in the simulations, we calculate variations of free energy of solvation of EM in partition of water/chloroform and water/methanol and obtained -2.6 and -4.9kcal/mol, respectively. This last result is in good agreement with the experimental result[3] of -5.6kcal/mol for partition of water/octanol. Finally, we performing calculations of UV-Vis absorption spectrum of isolated EM and in the three solutions. In this calculations, we considering the molecules through the continuum solvent (SCRF) and explicit solvent model with the method INDO/CIS. In this part, we obtaining that effect of solvent is well described theoretically.
Khan, Abdul Kareem. "Electrostaticanalisys the Ras active site." Doctoral thesis, Universitat Pompeu Fabra, 2009. http://hdl.handle.net/10803/7161.
Full textRas es una proteïna essencial de senyalització i actúa com un interruptor cel.lular. Les característiques estructurals de Ras en el seu estat actiu (ON) són diferents de les que té a l'estat inactiu (OFF). En aquesta tesi es duu a terme una anàlisi exhaustiva de l'estabilitat dels residus del centre actiu deRas en l'estat actiu i inactiu.
The electrostatic preorganization of the active site has been put forward as the general framework of action of enzymes. Thus, enzymes would position "strategic" residues in such a way to be prepared to catalyze reactions by
interacting in a stronger way with the transition state, in this way decreasing the activation energy g cat for the catalytic process. It has been proposed that
such electrostatic preorientation should be shown by analyzing the electrostatic stability of individual residues in the active site.
Ras protein is an essential signaling molecule and functions as a switch in the
cell. The structural features of the Ras protein in its active state (ON state) are different than those in its inactive state (OFF state). In this thesis, an exhaustive analysis of the stability of residues in the active and inactive Ras active site is performed.
Duignan, Timothy Thomas. "Modelling specific ion effects with the continuum solvent." Phd thesis, 2015. http://hdl.handle.net/1885/13642.
Full textJirkal, Štěpán. "Aplikace solvatačního modelu k popisu retence vybraných látek v kapalinové a plynové chromatografii." Doctoral thesis, 2016. http://www.nusl.cz/ntk/nusl-353446.
Full textTaraba, Lukáš. "Chromatografická charakterizace polyanilinem potažených stacionárních fází." Doctoral thesis, 2018. http://www.nusl.cz/ntk/nusl-389085.
Full text