Osmometric and viscometric study of levan, β-lactoglobulin and their mixtures

Determination of specific and non-specific protein–protein interactions for beta-lactoglobulin by analytical ultracentrifugation and membrane osmometry experiments

“…The volume of the stock solution was exchanged 10 times with the corresponding, pH adjusted sodium chloride solution. The diafiltration was performed according to Hundschell et al 51 To remove any potential protein aggregates, the diafiltered samples were centrifuged for 30 min at 4 °C and 10 000 g . The residue was discarded and the protein concentration of the supernatant was determined by measuring the absorbance at 278 nm with a Helios Omega UV-vis spectrophotometer (Thermo Fisher Scientific, Waltham Massachusetts, USA) using a specific extinction coefficient of 0.96 L (g cm) −1 .…”

“…Osmotic pressure measurements were performed at various protein concentrations as previously described by Hundschell et al 51 The osmotic second virial coefficient was determined using eqn ( 12)-( 14).…”

“…The molar mass in eqn (8) depends on the degree of dimerization in a monomer–dimer equilibrium system like BLG, and can be represented by:Here, w M and w D are the weight fractions and M M and M D represent the molecular mass of the monomer and the dimer, with M M = 0.5 M D and w M = 1 − w D . If the concentration is sufficiently low and higher order interactions can be neglected, the reduced osmotic pressure of a monomer–dimer system is given by: 51 The weight concentration of the protein is denoted c w . According to Schaink and Smit (2000), 52 the weight fraction w D for an ideal protein solution is given by: 51 By insertion of eqn (14) into eqn (13) and correcting for the reduced osmotic pressure by subtracting the molecular weight-dependent term in eqn (13), B 22 can be determined in the case of known osmotic pressure and dissociation constant K D .…”

“…If the concentration is sufficiently low and higher order interactions can be neglected, the reduced osmotic pressure of a monomer–dimer system is given by: 51 The weight concentration of the protein is denoted c w . According to Schaink and Smit (2000), 52 the weight fraction w D for an ideal protein solution is given by: 51 By insertion of eqn (14) into eqn (13) and correcting for the reduced osmotic pressure by subtracting the molecular weight-dependent term in eqn (13), B 22 can be determined in the case of known osmotic pressure and dissociation constant K D . When the molecular weight corrected osmotic pressure is plotted against the protein concentration, a straight line is obtained with a y -intercept at zero protein concentration.…”

Influence of Levan on the Thermally Induced Gel Formation of β-Lactoglobulin

“…To predict the structure and functionality of foods as complex multiphase systems, the understanding of the molecular interactions between the two main types of food biopolymers-polysaccharides and proteins-is of central importance, and therefore, part of ongoing research [1][2][3][4][5]. In systems consisting of two different polymer species, cosolubility, complexation, or thermodynamic incompatibility may occur, depending on the molecular interactions [6].…”