A-Lactalbumin 3-Lactoglobulin

Elfagm, A. A. and Wheelock, J. V. 1978B. Heat interaction between a-lactalbumin, /3-lactoglobulin, and casein in bovine milk. J. Dairy Sci. 61, 159-163. 

Super Q (strong anion exchange, 35 /r particles) EGTA, IDA (iminodiacetic acid) a-lactalbumin, /3-lactoglobulins A and B 48... 

For the anion exchanger experiment, a gradient mode with change in NaCl concentration was used to separate whey proteins of a-lactalbumin, 3-lactoglobulin, and BSA. The protein standards were used and the strong anion exchange membranes used in this experiment were CIM QA (BIA Separation Co.), QlOO (Sartorius), and HiTrap Q (Pharmacia). The mobile phases were buffer A (20 mm piperazine-HCl, pH 6.4) and buffer B (buffer A. + I M NaCl). In this experiment, the sample of whey was injected only with filtered 0.45 pm PVDF, without... 

J. Chandrapala, B. Zisu, S. Kentish, M. Ashokkumar, The effects of high-intensity ultrasound on the structural and functional properties of a-Lactalbumin, )3-Lactoglobulin and their mixtures. Food Res. Int. 48, 940-943 (2012)... 

Fig. 1 Ion-exchange chromatography of whey proteins on a Mono Q column using different buffer systems (A) a 100-/rl sample of total whey protein dissolved in 0.05 M sodium acetate buffer, pH 6.3, was injected into the column and eluted with a 0.05-0.7 M sodium acetate linear ionic-strength gradient for (B) and (C) the sample was dissolved in 0.02 M Tris-HCl, pH 7 (B) or pH 8 (C), and a 0-0.35 M NaCl linear gradient was applied. Key 1 immunoglobulins, 2 a-lactalbumin, 3 bovine serum albumin, 4 /3-lac-toglobulin B, 5 /3-lactoglobulin A. (From Ref. 37.)...

Comparison of the solubility of all three esterified proteins showed that the magnitude of the shift in the isoelectric points decreased in the following order (3-lactoglobulin > a-lactalbumin > (3-cascin. 

The influence of pH, ionic strength, and protein concentration on the extraction of a-lactalbumin and 3-lactoglobulin from an aqueous solution with water/AOT/isooctane microemulsions and their separation has been reported [168],... 

Caseins are highly disordered proteins having rather limited secondary structure. This is mainly due to the unusually high proline content, which is fairly uniformly distributed along the polypeptide chain. This feature leads to an open extended structure of the casein molecules which differentiates them from the globular whey proteins like a-lactalbumin and (3-lactoglobulin. The caseins have been described as rheomorphic ... 

In contrast, the whey proteins are relatively small globular proteins. a-Lactalbumin represents about 20 % of the protein content of bovine whey (3.5 % of total bovine milk protein), and it is the principal protein in human milk (Brew and Grobler, 1992). Nanotube assembly has been discovered in some solutions containing a hydrolysed derivative of this protein. And it appears that the a-lactalbumin nanotube is unique in the sense that it is the only artificial nanotube that has so far been made from a food protein (Graveland-Bikker et al., 2004 Graveland-Bikker and de Kruif, 2006). As for p-lactoglobulin, it has the capacity under certain specific conditions to form nano-fibres in aqueous media (as can various other globular food proteins, such as ovalbumin, soy proteins, and bovine serum albumin) (van der Linden, 2006 Nicolai, 2007). 

The proteins of milk fall into several classes of polypeptide chains. These have been delineated most completely in bovine milk, and a system of nonmenclature has been developed for them (Chapter 3 Eigel et al. 1984). One group, called caseins, consists of four kinds of polypeptides asr, as2-. and 3-, and k- with some genetic variants, post translational modifications, and products of proteolysis. Almost all of the caseins are associated with calcium and phosphate in micelles 20-300 fim in diameter (see Chapter 9). The other milk proteins, called whey proteins, are a diverse group including /3-lactoglobulin, a-lactalbumin, blood serum albumin, and immunoglobulins (Chapter 3). Almost all... 

Aschaffenburg, R. and Drewry, J. 1957B. Improved method for the preparation of crystalline /3-lactoglobulin and a-lactalbumin from cows milk. Biochem. J. 65, 273-277. 

Gobrinoff, M. J. 1967. Exposusre of tyrosine residues in proteins. Reaction of cyanuric fluoride with ribonuclease, a-lactalbumin, and /3-lactoglobulin. Biochemistry 66, 1606-1614. 

Robbins, F. M. and Kronman, M. J. 1964. A simplified method for preparing a-lactalbumin and /3-lactoglobulin from cows milk. Biochim. Biophys. Acta 82, 186-188. 

Fluid milk contains approximately 3.5% protein (USDA, CFEI 1976). Casein, found only in milk, comprises about 82% of the total milk protein, and whey proteins, principally /3-lactoglobulin and a-lactalbumin, constitute the remaining 18% (Lampert 1975 Jonas et al. 1976). Casein, because of its excellent nutritional value, is used routinely as a reference protein to evaluate the quality of protein in other foods (Jonas et al. 1976 Hambraeus 1982). 

About 20% of milk protein is soluble in the aqueous phase of milk. These serum proteins are primarily a mixture of /3-lactoglobulin, a-lactalbumin, bovine serum albumin, and immunoglobulins. Each of these globular proteins has a unique set of characteristics as a result of its amino acid sequence (Swaisgood 1982). As a group, they are more heat sensitive and less calcium sensitive than caseins (Kinsella 1984). Some of these characteristics (Table 11.1) cause large differences in susceptibility to denaturation (de Wit and Klarenbeek 1984). 

The primary proteins in milk are the caseins. These may be removed from milk by acid and heat-induced precipitation at pH 4.6 followed by centrifugation. The remaining supernatant (called whey) contains primarily a-lactalbumin and /3-lactoglobulin. These two proteins may be separated by gel filtration or with a Cu(II)—IDA-agarose affinity column. 

E Dumay, JC Cheftel. Chauffage d un concentre proteique de /3-lactoglobuline en milieu faiblement alcalin. Effets sur la solubilite et le comportement chromatographique de la /3-lactoglobuline et de l a-lactalbumine. Sci Aliments 9 561-582, 1989. 

GO Regester, GW Smithers. Seasonal changes in the /3-lactoglobulin, a-lactalbumin, glycomacro-peptide, and casein content of whey protein concentration. J Dairy Sci 74 796-802, 1991. 

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