Browsing by Author "Mota, Paula C."
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- Densidade e velocidade do som em soluções aquosas de sulfato de amónio contendo serina ou treoninaPublication . Mota, Paula C.; Pinho, Simão; Ferreira, Olga; Cibulka, IvanNeste trabalho faz-se uma breve apresentação das aplicações industriais dos aminoácidos e relevância do estudo de soluções aquosas contendo aminoácidos, em particular da serina ou da treonina. Estudar a interação de compostos modelo é importante pois tanto os aminoácidos, como péptidos, e seus derivados, constituem parte das estruturas das proteínas. Nesse sentido, foram estudadas as metodologias experimentais que permitem determinar a densidade e a velocidade do som. As propriedades derivadas como volumes molares parciais e compressibilidade adiabática são interpretadas em termos de química-fisica das soluções. Neste trabalho foram realizadas medições experimentais da densidade e velocidade do som em soluções aquosas de sulfato de amónio, a diferentes molalidades, contendo serina ou treonina, a cinco temperaturas diferentes, numa gama entre 278.15 K a 318.15 K. A partir destes dados, foram calculados os volumes molares parciais dos aminoácidos em estudo, de modo a compreender as propriedades físico-químicas das soluções. É também apresentado todo o desenvolvimento experimental, bem como os resultados obtidos e a interpretação teórica dos fenómenos. This work makes a brief presentation of industrial applications and relevance of amino acids, and studies of aqueous solutions containing amino acids, in particular with serine or threonine. The study of model compounds such as amino acids, peptides or their derivatives, as they constitute part of protein structures, is of extreme importance. Accordingly, the experimental methodologies for measuring the density and sound speed were studied. The properties derived such as partial molar volumes and adiabatic compressibility are interpreted in terms of the physical-chemistry of solutions. In this work, experimental values for the density and speed of sound in aqueous solutions of ammonium sulphate at different molalidades, containing serine or threonine, at five different temperatures in a range between 278.15 K to 318.15 K were measured. From these data, partial molar volumes of the amino acids were calculated. From the detailed analysis of that data the physical-chemistry of the solutions was interpreted. It is also presented, carefully, the intensive experimental development, adapted protocol and the theoretical analysis and graphical interpretations of phenomena.
- Partial molar volumes of amino acids in aqueous solutions containing ammonium sulfatePublication . Martins, M.A.; Mota, Paula C.; Ferreira, Olga; Hnědkovský, Lubomír; Pinho, Simão; Cibulka, IvanBecause proteins are large complex molecules direct study of protein-electrolyte interactions is difficult. It is therefore useful investigate the interaction of model coumpounds such amino acids, peptides has strongly attracting the attention researchers to describe their physico-chemical properties.
- Partial molar volumes of l-serine and l-threonine in aqueous ammonium sulfate solutions at (278.15, 288.15, 298.15, and 308.15) KPublication . Mota, Paula C.; Ferreira, Olga; Hnědkovský, Lubomír; Pinho, Simão; Cibulka, IvanIn this study, the partial molar volumes of L-serine and L-threonine in aqueous solutions of ammonium sulfate at (0.0, 0.1, 0.3, 0.7, and 1.0) mol.kg(-1) are reported between 278.15 and 308.15 K. Transfer volumes and hydration numbers were obtained, which are larger in L-serine than in L-threonine. Dehydration of the amino acids is observed, rising with the temperature and salt molality. The data suggest that interactions between ions and charged/hydrophilic groups are predominant, and by applying the McMillan and Mayer formalism, it was concluded that they are mainly pair wise. The combination of the data presented in this study with solubility and molecular dynamics data suggests a stronger interaction of the ammonium cation with the zwitterionic centers of the amino acids when compared to the interactions of those centers with the sulfate anion.