RESUMEN
The partitioning behavior of pentacyanonitrosilmetallate complexes[Fe(CN) 5 NO] (2-), [Mn(CN) 5 NO] 3(-), and [Cr(CN) 5 NO] 3(-)has been studied in aqueous two-phase systems (ATPS) formed by adding poly(ethylene oxide) (PEO; 4000 g mol (-1)) to an aqueous salt solution (Li2 SO4, Na2 SO4, CuSO4, or ZnSO4). The complexes partition coefficients ( K complex) in each of these ATPS have been determined as a function of increasing tie-line length (TLL) and temperature. Unlike the partition behavior of most ions, [Fe(CN) 5 NO] 2(-) and [Mn(CN) 5 NO] 3(-) anions are concentrated in the polymer-rich phase with K values depending on the nature of the central atom as follows: K [Fe(C N) 5 NO] 2 - >> K [ Mn (CN 5 NO] 3 - > K [C r (C N) 5 NO ]3 - . The effect of ATPS salts in the complex partitioning behavior has also been verified following the order Li2 SO 4 > Na2 SO 4 > ZnSO4. Thermodynamic analysis revealed that the presence of anions in the polymer-rich phase is caused by an EO-[M(CN) 5 NO] ( x- ) (M = Fe, Mn, or Cr) enthalpic interaction. However, when this enthalpic interaction is weak, as in the case of the [Cr(CN) 5 NO]3(-) anion ( K [Cr(CN 5 NO] 3 - < 1), entropic driving forces dominate the transfer process, then causing the anions to concentrate in the salt-rich phase.
RESUMEN
This study evaluates the influence of type of salt and temperature on the partition coefficient of caseinomacropetide (CMP) to determine the best conditions for the recovery of CMP in aqueous two-phase systems (ATPS) composed by poly(ethylene glycol) (PEG) 1500 and an inorganic salt (potassium phosphate, sodium citrate, lithium sulfate or sodium sulfate). In all systems, CMP presented affinity for the PEG-rich phase. The PEG1500+lithium sulfate showed the highest values of partitioning coefficient. In addition, thermodynamic parameters (DeltaH degrees , DeltaS degrees , DeltaG degrees) as a function of temperature, were calculated for the system PEG1500-sodium citrate at different PEG concentrations and the results imply thermodynamic differences between partitioning of CMP in this system.
Asunto(s)
Caseínas/química , Fraccionamiento Químico/métodos , Fragmentos de Péptidos/química , Polietilenglicoles/química , Sales (Química)/química , Temperatura , Termodinámica , Agua/químicaRESUMEN
Ions are known to concentrate in the salt-enriched phase of aqueous two-phase systems, with the only known exception being the pertechnetate anion, TcO(4)(-). We have discovered a second ion, nitroprusside anion (NP), which is markedly transferred from the salt phase to the polymer phase. The partitioning behavior of [Fe(CN)(5)NO](2-) anion was investigated in ATPS formed by poly(ethylene oxide) of molar mass 3350 and 35000 g mol(-1), and different sulfate salts (Na(2)SO(4), Li(2)SO(4), and MgSO(4)). On the basis of a model, the nitroprusside high affinity for the macromolecular phase was attributed to an enthalpic specific interaction between the anion and ethylene oxide unit. Partition coefficients increased exponentially with tie-line length increase, reaching values as high as 1000 and showing a relationship very dependent on the salt nature, but independent of the polymer molar mass.
Asunto(s)
Ferrocianuros/química , Nitroprusiato/química , Polietilenglicoles/química , Sulfatos/química , Agua/química , Aniones , Soluciones/química , TermodinámicaRESUMEN
The adsorptive behavior of bovine serum albumin (BSA) and beta-lactoglobulin (beta-lg) on hydrophobic adsorbent was studied at four temperatures and different salt concentrations. The Langmuir model was fitted by experimental equilibrium data showing that an increase in temperature and salt concentration results in an increase on the capacity factor of both proteins. A thermodynamic analysis coupled with isotherm measurements showed that salt concentration and temperature affected the enthalpic and entropic behavior of the adsorption process of both proteins, mainly to the beta-lg. The fast variation in the Z value for temperature over than 303.1K suggest a great conformational change occurring in the beta-lg structure, which almost duplicated the maximum adsorption capacity of this protein.
Asunto(s)
Lactoglobulinas/química , Sales (Química)/química , Albúmina Sérica Bovina/química , Termodinámica , Adsorción , Modelos Teóricos , Conformación ProteicaRESUMEN
The b-lactoglobulin and alfa-lactalbumin whey proteins were separeted by liquid-liquid extraction using a 14 per cent polyethylene glycol 1550 - 18 per cent potassium phosphate phase system. The selection of the aqueous two-phase system was based on the phase ratio ant the protein partition coefficient. The proteins were quantified employing a Fast Protein Liquid Chromatography system