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The partitioning of the whey protein lactoferrin, which is an iron transporter glycoprotein, in an aqueous two-phase system composed of poly(ethylene glycol) (PEG) and sodium citrate was evaluated. Equilibrium data at 25 °C were determined for each system studied using PEG with a molar mass of 1000 and 4000 g·mol1 at pH values of 5.5, 6.5, and 7.5. An increase in the molar mass of the polymer promoted the expansion of the two-phase region and caused the migration of the lactoferrin to the salt-rich bottom phase. An increase in pH also led to the expansion of the biphasic region. However, changing the pH over the tested range slightly affected protein partitioning. Lactoferrin recovery percentages greater than 94% were observed for all of the systems evaluated. The results indicated that lactoferrin can be successfully partitioned in an aqueous two-phase system formed of 14% (w/w) PEG and 10% (w/w) sodium citrate at pH 5.5 and 25 °C. The protein was concentrated 1000-fold in the salt-rich bottom phase in this system., Brazilian agencies FAPESB,CNPq, and FAPEMIG for their financial support

Phospholipases comprise a group of enzymes with applications in the thermal stability and emulsifying capacity of food formulations. In this work aqueous two-phase systems (ATPS) were used to extract phospholipase A 2 (PLA 2 ) from raw porcine pancreas and snake venom at 25 °C. PLA 2 was partitioned into ATPS composed of inorganic salts, water and polyethylene glycol. We determined the partition coefficient, recovery factor, purification factor, enzyme activity and emulsifying activity for the enzyme extracted with the different ATPS tested. The highest partition coefficient ( K p = 81.7) and the highest theoretical recovery percentage of PLA 2 in the top and bottom phases of the systems were obtained from the pancreas extract. The highest recovery percentage in the top phase was obtained in a system with PEG1500/Na 2 SO 4 /H 2 O. Pearson correlation analysis between the ATPS descriptor parameters and the recovery and partitioning parameters of PLA 2 showed significant, albeit small, correlation between molar mass and PEG phase volume. Furthermore, Principal Component Analysis showed that the best system for PLA 2 purification was with ATPS PEG1500/Na 2 SO 4 /H 2 O. In addition to preserving enzyme activity, the ATPS provided a high partition coefficient of PLA 2 (81.67%) and can be considered a viable technique for pre-purification of PLA 2 .

The study of protein interactions has generated great interest in the food industry. Therefore, research on new supramolecular structures shows promise. Supramolecular structures of the whey proteins {\alpha}-lactalbumin and glycomacropeptide were produced under varying heat treatments (25 to 75 {\deg}C) and acidic conditions (pH 3.5 to 6.5). Isothermal titration calorimetry experiments showed protein interactions and demonstrated that this is an enthalpically driven process. Supramolecular protein structures in aqueous solutions were characterized by circular dichroism and intrinsic fluorescence spectroscopy. Additional photon correlation spectroscopy experiments showed that the size distribution of the structures ranged from 4 to 3545 nm among the different conditions. At higher temperatures, lower pH increased particle size. The foamability of the supramolecular protein structures was evaluated. Analysis of variance and analysis of regression for foaming properties indicated that the two-factor interactions between pH and temperature exhibited a significant effect on the volume and stability of the foam., Comment: 9 pages, 5 figures

The effect of different ionic cosolutes (NaCl, Na$_2$SO$_4$, Li$_2$SO$_4$, NaSCN, Na$_2$[Fe(CN)5NO], and Na$_3$[Co(NO)$_6$]) on the interaction between sodium dodecyl sulfate (SDS) and poly(ethylene oxide) (PEO) was examined by small-angle X-ray scattering (SAXS) and isothermal titration calorimetric techniques. The critical aggregation concentration values (cac), the saturation concentration ($C_2$), the integral enthalpy change for aggregate formation ($\Delta H_{\mbox{agg}}$(int)) and the standard free energy change of micelle adsorption on the macromolecule chain ( $\Delta\Delta G_{\mbox{agg}}$) were derived from the calorimetric titration curves. In the presence of 1.00 mmol L$^{-1}$ cosolute, no changes in the parameters were observed when compared with those obtained for SDS-PEO interactions in pure water. For NaCl, Na$_2$SO$_4$, Li$_2$SO$_4$, and NaSCN at 10.0 and 100 mmol L$^{-1}$, the cosolute presence lowered cac, increased $C_2$, and the PEO-SDS aggregate became more stable. In the presence of Na$_2$[Fe(CN)5NO], the calorimetric titration curves changed drastically, showing a possible reduction in the PEO-SDS degree of interaction, possibility disrupting the formed nanostructure; however, the SAXS data confirmed, independent of the small energy observed, the presence of aggregates adsorbed on the polymer chain., Comment: 8 pages, 8 figures