The Quaternary Structure of Bovine alpha-Crystallin. Effects of Variation in Alkaline pH, Ionic Strength, Temperature and Calcium Ion Concentration

A systematical quantitative understanding of different mechanisms, though of fundamental importance for better fouling control, is still unavailable for the microfiltration (MF) of humic acid (HA) and protein mixtures. Based on extended Derjaguin–Landau–Verwey–Overbeek (xDLVO) theory, the major fouling mechanisms, i.e., Lifshitz–van der Waals (LW), electrostatic (EL), and acid–base (AB) interactions, were for the first time quantitatively analyzed for model HA–bovine serum albumin (BSA) mixtures at different solution conditions. Results indicated that the pH, ionic strength, and calcium ion concentration of the solution significantly affected the physicochemical properties and the interaction energy between the polyethersulfone (PES) membrane and HA–BSA mixtures. The free energy of cohesion of the HA–BSA mixtures was minimum at pH = 3.0, ionic strength = 100 mM, and c(Ca2+) = 1.0 mM. The AB interaction energy was a key contributor to the total interaction energy when the separation distance between the membrane surface and HA–BSA mixtures was less than 3 nm, while the influence of EL interaction energy was of less importance to the total interaction energy. The attractive interaction energies of membrane–foulant and foulant–foulant increased at low pH, high ionic strength, and calcium ion concentration, thus aggravating membrane fouling, which was supported by the fouling experimental results. The obtained findings would provide valuable insights for the quantitative understanding of membrane fouling mechanisms of mixed organics during MF.

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Calcium Ion Concentration in Milk, Whey, and β-Lactoglobulin as Influenced by Ionic Strength, Added Calcium, Rennet Concentration, and Heat

Journal of Dairy Science ◽

10.3168/jds.s0022-0302(69)86812-8 ◽

1969 ◽

Vol 52 (10) ◽

pp. 1672-1675 ◽

Cited By ~ 13

Author(s):

B.J. Demott

Keyword(s):

Ionic Strength ◽

Calcium Ion ◽

Ion Concentration ◽

Milk Whey ◽

Calcium Ion Concentration ◽

Β Lactoglobulin

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The action of rennets on the caseins: I. Rennin action on β-casein-B in solution

Journal of Dairy Research ◽

10.1017/s0022029900019385 ◽

1971 ◽

Vol 38 (3) ◽

pp. 269-280 ◽

Cited By ~ 31

Author(s):

L. K. Creamer ◽

O. E. Mills ◽

E. L. Richards

Keyword(s):

Ionic Strength ◽

Conformational Changes ◽

Calcium Ion ◽

Ion Concentration ◽

Disk Electrophoresis ◽

C Terminus ◽

Rate Of Hydrolysis ◽

Calcium Ion Concentration ◽

Hydrolysis Of ◽

Electrophoresis Technique

SummaryA study of the hydrolysis of β-casein-B by crystalline rennin or rennet extract at pH 6·5, using a disk electrophoresis technique, showed that 3 bonds in β-casein are appreciably more sensitive than the others to rennin proteolysis, and that these bonds are probably located near the C-terminus of the protein. The most susceptible bond is hydrolysed, at 10°C, about 200 times faster than any other bond, whilst at 37°C it is hydrolysed 60 times faster. A study of the hydrolysis of this bond showed that its rate of hydrolysis at 37°C and pH 6·5 is decreased by either increased ionic strength or increased calcium ion concentration at constant ionic strength. Conformational changes in the substrate are probably responsible for these effects.

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Coagulation of renneted bovine casein micelles: dependence on temperature, calcium ion concentration and ionic strength

Journal of Dairy Research ◽

10.1017/s0022029900023165 ◽

1983 ◽

Vol 50 (3) ◽

pp. 331-340 ◽

Cited By ~ 120

Author(s):

Douglas G. Dalgleish

Keyword(s):

Ionic Strength ◽

Calcium Ion ◽

Maximum Rate ◽

Bond Formation ◽

Ion Concentration ◽

Ionic Interactions ◽

Maximal Rate ◽

Casein Micelles ◽

Hydrophobic Bond ◽

Calcium Ion Concentration

SummaryThe rates of coagulation of completely renneted casein micelles have been measured as functions of ionic strength, temperature, and concentration of Ca2+. At 25 °C and below, the rate constants for the coagulation were found to be low, but increased with temperature so that at 60 °C the particles were coagulating at almost maximum rate permitted by diffusion. This maximal rate at 60 °C was achieved at nearly all of the ionic strengths and concentrations of Ca2+ used. At lower temperatures the rate constant decreased with increasing ionic strength, the dependence being more marked at lower temperatures. Increasing concentration of Ca2+ also increased the rate at low and moderate temperatures. The implications of these results are discussed in terms of specific and non-specific ionic interactions and of hydrophobic bond formation.

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