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| Author(s): |
Weslley Guilherme Dias de Paiva Silva
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Química |
| Defense date: | 2017-07-17 |
| Examining board members: |
Roberto Rittner Neto;
Ernani Abicht Basso;
Anita Jocelyne Marsaioli
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| Advisor: | Roberto Rittner Neto |
| Abstract | |
The understanding of the conformational behavior of the amino acids and their derivatives is a challenge task, since several effects can affect their conformational preferences. In the present work, the conformational analysis of esterified and N-acetylated derivatives of methionine and glutamic acid using a combination of ¹H NMR spectroscopy and electronic structure calculations is reported as an alternative for the study of amino acids in solution. The studied derivatives are soluble in the most of organic solvents and thus, their study can represent a reasonable approximation to the behavior of an amino acid residue into a polypeptide chain. The geometries and energies of the most stable conformers in isolated phase and taking into account the implicit solvent effects, according to the integral equation formalism polarizable continuum model (IEF-PCM) were obtained at the 'omega'B97X-D/aug-cc-pVTZ level of theory. The conformational equilibrium of the compounds in solution were also determined from experimental and theoretical NMR data using ³JHH spin-spin coupling constants in different organic solvents. A comparison between the experimental and theoretical coupling constants indicate that the conformational stability of the esterified derivative of methionine (MetOEt) is not very sensitive to solvent polarity, whereas the conformers of the N-acetylated derivate of methionine as well as the esterified and N-acetylated derivates of glutamic acid (GluOMe and AcGluOMe) had their populations changed when the polarity of the medium was varied from CHCl3 to DMSO. According to the Natural Bond Orbital (NBO), Quantum Theory of Atoms in Molecules (QTAIM) and Noncovalent Interactions (NCI) analyses, the conformational preferences for the studied compounds are not dictated by an specific interaction, but due to a combination of hyperconjugative and steric interactions (AU) | |
| FAPESP's process: | 16/12005-5 - Conformational analyses of aminoacids derivatives: a theoretical and experimental approach |
| Grantee: | Weslley Guilherme Dias de Paiva Silva |
| Support Opportunities: | Scholarships in Brazil - Master |