A-Lactoglobulin

Carboxyl groups absorb at about 1710 cm1, and carboxylates at about 1570 cm-1. Infrared difference spectra in D20 solutions have been used to measure the pA s of abnormal carboxyl groups in a-lactoglobulin (7.5) and lysozyme (2.0, 6.5). 

Figure B3.1.3 An isoelectric focusing (IEF) gel, pH 3 to 10. Lane 1, 4 pg purified egg white cystatin. Lane M, broad-range pi standards trypsinogen (pi 9.3), lentil lectin-basic band (pi 8.65), lentil lectin-middle band (pi 8.45), lentil lectin-acidic band (pi 8.15), myoglobin-basic band (pi 7.35 visible as a broad band), myoglobin-acidic band (pi 6.85), human carbonic anhydrase B (pi 6.55), bovine carbonic anhydrase (pi 5.85), a-lactoglobulin A (pi 5.20), soybean trypsin inhibitor (pi 4.55), and amyloglucosidase (pi 3.50) in order shown from top of gel. The pi values of the two purified egg white cystatin isomers were determined to be 6.6 (upper band) and 5.8 (lower band). Adapted from Akpinar (1998) with permission from author.

Lysozyme trypsinogen myoglobin (5-lactoglobulin A -lactoglobulin B Open-tubular UV 25... 

Pellegrini, A., Dettling, C., Thomas, U., and Hunziker, P. 2001. Isolation and characterization of four bactericidal domains in the bovine a-lactoglobulin. Biochim. Biophys. Acta 1526, 131-140. 

The production of WPC by UF is today a well-established application in the food and dairy industry. WPC can be further fractionated in j3- and a-lactoglobulin fractions by properly selectingpH,ionicstrength and temperature (Zidney, 1998), or used for the manufacture of caseino-macropeptides with pharmotherapeutic value. 

Allergic symptoms have been reported for casein fractions and serum (whey) globulins of cow s milk. The most important allergens include a- and P-casein and P-lactoglobuhn. Allergic effects have also been seen in a-lactoglobulin and a-lactalbumin. 

Figure 20. Surface charge density, Qads A lactoglobulin A at a platinum electrcxle as a function of the concentration (w/v) of the protein in phosphate buffer (pH 7.0) with an anodic end potential of 0.4 V at various temperatures, o, 299 K , 343 K , denatured at 343 K, then cooled to 299 K. (Reprinted from Roscoe et al with permission.)...

Figure 24. Surface charge density,of protein at a platinum electrode versus the time of potential sweeping after the electrode was dipped in protein solution(s) in phosphate buffer (pH 7.0,368 K) and measured at 273 K. , dipped in a /c-casein solution (0.13 g r ) A, dipped first in the K-casein solution and then in a -lactoglobulin solution (0.16 g 1" 2 min dip each v, dipped first in the /c-casein solution followed by the jff-lactoglobulin solution, 8 min dip each , dipped first in the )ff-lactoglobulin solution followed by the /c-casein solution, 2 min dip each O, dipped first in the J -lactoglobulin solution followed by the /c-casein solution, 8 min dip each. (Reprinted from Roscoe and Fuller with permission.)...

Saponins also affect the permeability of intestinal cells by forming addition complexes with sterols (e.g. cholesterol) in mucosal cell membranes [7]. This leads to destabilization of the membranes and an increase in the permeability of intestinal mucosal cells, which inhibit active nutrient transport. Thus this facilitates the uptake of substances to which the gut would normally be impermeable, e.g. milk alergen a-lactoglobulin. 

---