Salt effect on the (polyethylene glycol 8000 + sodium sulfate) aqueoustwo-phase system : relative hydrophobicity of the equilibrium phases

The relative hydrophobicity of the phases of several {polyethylene glycol (PEG) 8000 + sodium sulfate (Na2SO4)} aqueous two-phase systems (ATPSs), all containing 0.01 mol.L-1 sodium phosphate buffer (NaPB, pH 7.4) and increasing concentration of a salt additive, NaCl or KCl, up to 1.0 mol.L-1, was measured by the free energy of transfer of a methylene group between the phases, DG(CH2). The DG(CH2) of the systems was determined by partitioning of a homologous series of five sodium salts of dinitrophenylated (DNP) – amino acids with aliphatic side chains in three different tie-lines of each biphasic system. The relative hydrophobicity of the phases ranged from -0.125 to -0.183 kcal.mol.L-1, being the NaCl salt the one to provide the more effective changes. The results show that, within each system, there is a linear relationship between the DG(CH2) and the tie-line length (TLL), and biphasic systems with high salt additive concentration present the most negative DG(CH2) values. Therefore, the feasibility of establishing a relationship between the relative hydrophobicity of the phases in a given TLL and the ionic strength of the salt additive was investigated and a satisfactory correlation was found for each salt.Luisa A. Ferreira acknowledges the financial support (SFRH/BPD/47607/2008) from Fundacao para a Ciencia e a Tecnologia (Lisboa, Portugal)

Salt effect on the aqueous two-phase system PEG 8000-sodium sulfate

The effect of added salt (NaCl or KCl) on the polyethylene glycol 8000 (PEG)−sodium sulfate (Na2SO4) aqueous two-phase system (ATPS), containing 0.01 mol·L−1 of sodium phosphate buffer (NaPB), pH 7.4, has been investigated at 296.15 K. Phase diagrams determined by the cloud point method, including tie-lines assigned from mass phase ratios according to the lever arm rule, are presented for the different PEG 8000−Na2SO4 ATPSs, all containing 0.01 mol·L−1 NaPB, pH 7.4, and increasing the concentration of a neutral salt, such as NaCl or KCl, up to 1.0 mol·L−1. Experimental binodal results were satisfactorily correlated with an empirical mathematical model, the Merchuk equation. The results indicate that the addition of both salts causes a depression of the binodal relatively to that for the salt-free system. The salting-out ability of the cations follows the Hofmeister series (Na+ > K+) and can be related to the ions Gibbs free energy of hydration (ΔGhyd).L.A.F. acknowledges the financial support (SFRH/BPD/47607/2008) from Fundacao para a Ciencia e a Tecnologia (Lisboa, Portugal)

Salt effect on the aqueous two-phase system PEG 8000 - sodium sulfate : physico-chemical characterization of the systems

Este resumo faz parte de: Book of abstracts of the Meeting of the Institute for Biotechnology and Bioengineering, 2, Braga, Portugal, 2010. A versão completa do livro de atas está disponível em: http://hdl.handle.net/1822/1096

The effect of the alcohol content on the solubility of amino acids in aqueous solutions

The solubility of me most simple a-amino acid, glycine, was measured in the temperature range between 25 and 60°C for the aqueous system of ethanol and at 25 °C for the aqueous system 0V 1-propanol. Theoretical work was essentially focused on the application of the excess solubility approach with conventional thermodynamic models such as the Margules and Wilson equations. The simple three suffix Margules model, with only one parameter to be estimated, gave the best results, with an average absolute deviation of 3.8%

Solubility of amino acids in mixed solvent systems

The solubilities of L-serine, L-threonine and L-isoleucine in the aqueous systems of ethanol, 1-propanol and 2-propanol were measured in the temperature range between 298.15 K and 333.15 K by means of a gravimetric method and a spectrophotometric technique based on a ninhydrin reaction. The solubility data from this work and from literature were used to explore the potentialities of the application of the excess solubility approach with the NRTL [1], modified NRTL [2], modified UNIQUAC [3, 4] equations and the model presented by Gude et al. (1996) [5, 6]. These four models give a global average relative deviation of 12.2 %, 12.0 %, 15.1 %, and 16.2 % for correlation and 16.3 %, 14.6 %, 27.3 %, and 22.0 % for prediction, respectively

Electrolyte effect on the solubility of amino acids in aqueous solutions

The precipitation and crystallization of biomolecules have been widely used for their separation and concentration. The presence of electrolytes in solution may affect significantly the solubilities of biochemicals, which has been used for salt-induced separation of proteins. Although amino acids are among the simplest biochemicals, they have many similarities with more complex biochemicals and are the building block of proteins. So, the study of the electrolyte effect In the solubility of amino acids in water is a good starting point for further developments. Although some studies have been published concerning the measurement and thermodynamic properties modeling of aqueous solutions of amino acids with electrolytes, the information available is very scarce. Therefore, in this work, the solubility of Glycine and OL-Alanine were measured in the temperature range between 25 and 60 °C for aqueous systems of KCI, Na2SO4 and (NH4)2S04, salts most often used in industrial separation processes. A comparison is given with values recently published in the literatures. It was possible to find out big discrepancies, and for the solubility of OL-Alanine in aqueous solutions an inverse dependence with the concentration of the KCI salt was obtained, The new experimental data were used together with information already available concerning the activity coefficients and solubilities, to explore the capabilities of a modified Wilson model, recently developed in our group, for the thermodynamic description of these complex systems. Despite the difficulties that arose for the description of these highly non-ideal systems, the results shown are satisfactory for the correlation of the solubilities

Modelling amino acid solubility in several aqueous alkanol solutions with the PC-SAFT EoS

Since their isolation in the 19th century the physical and chemical properties of amino acids became a very important studied subject, no only because of their value as basic elements in all forms of life but also for their industrial importance, particularly for food. Chemical, medical, pharmaceutical and cosmetics industries

European life project: a global strategy for the responsible use of a coastal lagoon: a case study from Portugal

Rin de Aveiro is a coastal lagoon located at the Central Region of Portugal subjected to the influence of the tides, resulting in a set of characteristic biotopes favouring anthropic and natural processes. Once managed and controlled correctly, each of these biotopes will allow simultaneously the biodiversity and integration in the making of the wetland landscape. In 1998, one of the final conclusions of the "MARIA" Demonstration Programme for the Integrated Management of Ria de Aveiro was that the poor current state of the environment area resulted from a set of interrelated factors. The Programme selected four (4) pilot-projects towards the integrated management of the lagoon biotopes as possible scenarios for an intervention. This selection was based in criteria related to environmental priorities and the maintenance of traditional economic activities in the region. The idea of choosing projects that would involve the whole geographic space of the Ria, without forgetting the other important themes interrelated with the Management Structure, emerged as a relevant aspect for their definition. Thus, and as a first test of this Management Structure functionality, the following task forces were put forward: Recovery and valorisation of the piers; Recovery of the former salt pans; Management of the agricultural fields of Baixo-Vouga; Implementation of measures for the classification of the Protected Landscape Area of the River Caster Mouth. This payer will report the main results of these pilot-projects attained during their first year period, especially the intervention strategies defined by the Partnership created for this aim

Peritumoural, but not intratumoural, lymphatic vessel density and invasion correlate with colorectal carcinoma poor-outcome markers

To evaluate whether lymphatic vessel density (LVD) and lymphatic vessel invasion (LVI) are useful markers of worse outcome in colorectal carcinoma and if LVD and LVI correlate to the classical clinical-pathological parameters, we analysed 120 cases of colorectal carcinomas selected from the files of Division of Pathology, Hospital das Clinicas, São Paulo University, Brazil. Assessment of LVD and LVI was performed by immunohistochemical detection of lymphatic vessels, using the monoclonal antibody D2-40. Higher LVD was found in the intratumoural area, when comparing with normal and peritumoural areas (p < 0.001). However, peritumoural LVD, but not intratumoural, correlated with both colonic-wall-invasion depth (p = 0.037) and liver metastasis (p = 0.012). Remarkably, LVI was found associated with local invasion (p = 0.016), nodal metastasis (p = 0.022) and hepatic metastasis (p < 0.001). Peritumoural LVD and LVI are directly related to histopathological variables indicative of poor outcome such as lymph-node status and liver metastasis