Browsing by Author "Gomes, J.R.B."
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- Computational and experimental study of the behavior of cyano-based ionic liquids in aqueous solutionPublication . Batista, Marta; Kurnia, Kiki A.; Pinho, Simão; Gomes, J.R.B.; Coutinho, João A.P.The solvation of cyano- (CN-) based ionic liquids (ILs) and their capacity to establish hydrogen bonds (H-bonds) with water was studied by means of experimental and computational approaches. Experimentally, water activity data were measured for aqueous solutions of ILs based on 1-butyl-3-methylimidazolium ([BMIM](+)) cation combined with one of the following anions: thiocyanate ([SCN](-)), dicyanamide ([DCA](-)), or tricyanomethanide ([TCM](-)), and of 1-ethyl-3-methylimidazolium tetracyanoborate ([EMIM][TCB]). From the latter data, water activity coefficients were estimated showing that [BMIM][SCN] and [BMIM][DCA], unlike [BMIM][TCM] and [EMIM][TCB], are able to establish favorable interactions with water. Computationally, the conductor like screening model for real solvents (COSMO-RS) was used to estimate the water activity coefficients which compare well with the experimental ones. From the COSMO-RS results, it is suggested that the polarity of each ion composing the ILs has a strong effect on the solvation phenomena. Furthermore, classical molecular dynamics (MD) simulations were performed for obtaining an atomic level picture of the local molecular neighborhood of the different species. From the experimental and computational data it is showed that increasing the number of CN groups in the ILs' anions does not enhance their ability to establish H-bonds with water but decreases their polarities, being [BMIM][DCA] and [BMIM][SCN] the ones presenting higher propensity to interact.
- Experimental and molecular dynamics simulation studies on thee solubilityof amino acids in aqueous electrolyte solutionsPublication . Tomé, L.I.N.; Pinho, Simão; Jorge, M.; Gomes, J.R.B.; Coutinho, João A.P.Separation and concentration of biological compounds are current subjects of interest due to their high cost in comparison to the total manufacture cost. For that purpose electrolytes may be employed as they can effect significantly biochemicals solubilities, a feature that has been used for salt-induced precipitation of proteins.
- Salting-in with a salting-out agent: explaining the cation specific effects on the aqueous solubility of amino acidsPublication . Tomé, L.I.N.; Pinho, Simão; Jorge, M.; Gomes, J.R.B.; Coutinho, João A.P.Although the understanding of ion specific effects on the aqueous solubilities of biomolecules is crucial for the development of many areas of biochemistry and life sciences, a consensual and well-supported molecular picture of the phenomena has not yet been established. Mostly, the influence of cations and the nature of the molecular interactions responsible for the reversal of the Hofmeister trend in aqueous solutions of amino acids and proteins are still defectively understood. Aiming at contributing to the understanding of the molecular-level mechanisms governing the cation specific effects on the aqueous solubilities of biocompounds, experimental solubility measurements and classical molecular dynamics simulations were performed for aqueous solutions of three amino acids (alanine, valine, and isoleucine), in the presence of a series of inorganic salts. The evidence gathered suggests that the mechanism by which salting-in inducing cations operate in aqueous solutions of amino acids is different from that of anions, and allows for a novel and consistent molecular description of the effect of the cation on the solubility based on specific interactions of the cations with the negatively charged moieties of the biomolecules.
- The cation effect on the aqueous solubility of amino acids in the presence of salts : experimental and molecular dynamics simulation studiesPublication . Tomé, L.I.N.; Pinho, Simão; Jorge, M.; Gomes, J.R.B.; Coutinho, João A.P.Aiming at contributing to the understanding the molecular level mechanisms governing the behavior of biocompounds in aqueous saline environments, experimental solubility measurements and molecular dynamics (MD) simulations were performed for aqueous solutions of three amino acids (alanine, valine and isoleucine) in the presence of a series of inorganic salts.
- The cation effect on the aqueous solubility of amino acids in the presence of salts : experimental and molecular dynamics simulation studiesPublication . Tomé, L.I.N.; Pinho, Simão; Jorge, M.; Gomes, J.R.B.; Coutinho, João A.P.The study of the solubility behavior of amino acids and proteins in aqueous electrolyte solutions is of utmost importance to understand the biochemistry of natural systems, develop medical and pharmaceutical responses to diseases induced by biochemical disorders and improve the efficiency of biotechnological processes. Although the effect of common salts on the aqueous solubility of amino acids and proteins is phenomenologically well described [1], the underlying molecular-level mechanisms are far from being elucidated and consensual, in spite of the several explanations proposed during the past century.
- Understanding the cation specific effects on the aqueous solubility of amino acids: from mono to polyvalent cationsPublication . Tomé, L.I.N.; Sousa, C.S.R.; Gomes, J.R.B.; Ferreira, Olga; Coutinho, João A.P.; Pinho, SimãoThe interactions established by mono and polyvalent cations in natural media have important implications on the structure formation, function and physico-chemical behavior of biomolecules, playing therefore a critical role in biochemical processes. In order to further elucidate the molecular phenomena behind the cation specific effects in biological environments, and clarify the influence of the charge of the ions, solubility measurements and molecular dynamics simulations were performed for aqueous solutions of three amino acids (alanine, valine and isoleucine), in the presence of a series of inorganic salts comprising mono-, di- and trivalent cations (LiCl, Li2SO4, K2SO4, CaCl2, AlCl3 and Al-2(SO4)(3)). The evidence gathered indicates that the mechanism by which (salting-in inducing) polyvalent cations affect the solubility of amino acids in aqueous solutions is different from that of monovalent cations. A consistent and refined molecular description of the effect of the cation on the solubility of amino acids based on specific interactions of the cations with the negatively charged moieties of the biomolecules is here proposed.
- Why are some cyano-based ionic liquids better glucose solvents than water?Publication . Batista, Marta; Passos, Helena; Henriques, Bruno J.M.; Maginn, Edward J.; Pinho, Simão; Freire, Mara G.; Gomes, J.R.B.; Coutinho, João A.P.Among different classes of ionic liquids (ILs), those with cyano-based anions have been of special interest due to their low viscosity and enhanced solvation ability for a large variety of compounds. Experimental results from this work reveal that the solubility of glucose in some of these ionic liquids may be higher than in water – a well-known solvent with enhanced capacity to dissolve mono- and disaccharides. This raises questions on the ability of cyano groups to establish strong hydrogen bonds with carbohydrates and on the optimal number of cyano groups at the IL anion that maximizes the solubility of glucose. In addition to experimental solubility data, these questions are addressed in this study using a combination of density functional theory (DFT) and molecular dynamics (MD) simulations. Through the calculation of the number of hydrogen bonds, coordination numbers, energies of interaction and radial and spatial distribution functions, it was possible to explain the experimental results and to show that the ability to favorably interact with glucose is driven by the polarity of each IL anion, with the optimal anion being dicyanamide.