Proteins lactoglobulin

The caseins are often considered to be rather hydrophobic molecules. However, consideration of the amino acid composition indicates that they are not particularly so in fact, some are more hydrophilic than the whey protein, /3-lactoglobulin (Table 4.2). However, the caseins do have high... 

Braunitzer, G., Chen, R., Schrank, B, and Stangl, A. 1972. Automatic sequential analysis of a protein (/3-lactoglobulin AB). Hoppe-Seyler s Z. Physiol. Chem. 353, 832-834 (German). 

McKenzie, H. A. 1971. Whey proteins and minor proteins (3-Lactoglobulins. In Milk Proteins Chemistry and Molecular Biology, Vol. 2. H.A. McKenzie (Editor). Academic Press, New York, pp. 257-330. 

Cell surfaces of body tissues appear to contain receptors for the retinol-binding protein. Many cells also contain cytoplasmic retinolbinding proteinss-u as well as proteins that bind retinoic acid.u-y These proteins are members of the large superfamily of hydro-phobic transporter molecules described in Box 21-A. This includes the milk protein 3-lactoglobulin, which also forms a complex with retinol.z,aa... 

M de Frutos, A Cifuentes, JC Diez-Masa. Multiple peaks in high-performance liquid chromatography of proteins /3-lactoglobulins eluted in a hydrophobic interaction chromatography system. J Chromatogr A 778 43-52, 1997. 

Study of heat denaturation of major whey proteins ((3-lactoglobulin or a-lactalbumin) either in separated purified forms, or in forms present in fresh industrial whey or in recomposed mixture respecting whey proportions has been recently carried out (Bertrand-Harb et al., 2002), indicating significant differences in their denaturation depending on pH,... 

FIGURE 9 Displacement chromatography on a retained pH gradient. The presaturation and elution buffers are formed by titrating 0.05 M NaOH with MOPS and acetic acid, respectively. Adsorbent TosoHaas TSK Q-5PW (5 /x particles) flow rate 0.1 mL/min proteins /3-lactoglobulins A and B (from Narahari et a/.,69 with permission from Elsevier Science). 

The interfacial behavior of protein-surfactant complexes is important in several areas such as the stability of emulsions and foams and the adsorption of proteins and surfactants from their binary solutions onto solid surfaces. Of particular interest is the adsorption of the milk proteins /3-lactoglobulin and /3-casein at the oil-water interface in the presence of nonionic surfactants in relation to food emulsions [56-58] and foam stability [59]. The adsorption of gelatin at the air-water [52,53,60], oil-water [6], and solid-water [62] interfaces in the presence of surfactants has also been studied. Other studies reported include adsorption from aqueous solutions of lysozyme plus ionic surfactants at solid surfaces [63,64], /3-lactoglobulin plus SDS onto... 

Dining an attempt to determine the molecnlar weight of the milk protein 3-lactoglobulin, by means of gel filtration, the following data were obtained with different sample concentrations ... 

RP-HPLC can be used to determine the extent of degradation of native whey proteins ( 3-lactoglobulin and a-lactalbumin) by enzymes and to study their kinetics of degradation by monitoring both the disappearance of a-lactalbumin and p-lactoglobuhn and the appearance of peptide products. " It can also be used to evaluate whether the chromatographic profile obtained is affected by... 

Values of for fatty acids bound to the soluble p-barrel protein, (3-lactoglobulin, are in the range 220-110 ns, decreasing with spin-label position down to C12 of the chain." However, it appears that the spin-label group does not enter fully into the binding pocket of p-lactoglo-bulin, which is less exposed to water than are the binding sites of serum albumin. 

The lactoglobulin fraction consists mainly of immunoglobulins (Ig), especially IgGj, with lesser amounts of IgG2, IgA and IgM (section 4.10). The lactalbumin fraction of bovine milk contains three main proteins, / -lactoglobulin (j8-lg), a-lactalbumin (a-la) and blood serum albumin (BSA), which represent approximately 50, 20 and 10% of total whey protein, respectively, and trace amounts of several other proteins, notably lactotrans-ferrin, serotransferrin and several enzymes. The whey proteins of sheep, goat... 

Whey protein Lactoglobulin, lactoalbumin Soluble under acid conditions. Emulsifying or foaming... 

Casein. Milk contains proteins and essential amino acids lacking in many other foods. Casein is the principal protein in the skimmed milk (nonfat) portion of milk (3—4% of the weight). After it is removed from the Hquid portion of milk, whey remains. Whey can be denatured by heat treatment of 85°C for 15 minutes. Various protein fractions are identified as a-, P-, and y-casein, and 5-lactoglobulin and blood—semm albumin, each having specific characteristics for various uses. Table 21 gives the concentration and composition of milk proteins. 

Godovac-Zimmerman, J. The structural motif of p-lactoglobulin and retinol-binding protein a basic framework for binding and transport of small hydrophobic molecules Trends Biochem. Sci. 

Papiz, M.Z., et al. The structure of p-lactoglobulin and its similarity to plasma retinol-binding protein. Nature 324 383-385, 1986. 

The proteolytic digestion of j6-lactoglobulin was carried out with trypsin which, as indicated in Table 5.4 above, is expected to cleave the polypeptide backbone at the carboxy-terminus side of lysine (K) and arginine (R). On this basis, and from the known sequence of the protein, nineteen peptide fragments would be expected, as shown in Table 5.7. Only 13 components were detected after HPLC separation and, of these, ten were chosen for further study, as shown in Table 5.8. 

Table 5.7 Theoretically predicted polypeptides from the trypsin digestion of S-lacto-globulin (/3LG) . Reprinted from J. Chromatogr., A, 763, Turula, V. E., Bishop, R. T., Ricker, R. D. and de Haseth, J. A., Complete structure elucidation of a globular protein by particle beam liquid chromatography-Fourier transform infrared spectrometry and electrospray liquid chromatography-mass spectrometry - Sequence and conformation of /3-lactoglobulin , 91-103, Copyright (1997), with permission from Elsevier Science...

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],... 

Mousavi, S. H., Bordbar, A. K., and Haertle, T. (2008). Changes in structure and in interactions of heat-treated bovine beta-lactoglobulin. Protein Pept. Lett. 15, 818-825. 

Four reconstituted milks were prepared by blending hydrated skim milk powder (35g/L) with four different emulsions (35g/L) differing by composition of the fat-water interface. Whole reconstituted milks were coded MP (milk proteins), BCAS ( 6-casein), and BLG5 (j6-lactoglobulin 5 g/L). 

Reconstituted milks with natural milk fat globules (CREAM) or emulsified milk fat droplets stabilized by jS-casein (BCAS), /i-lactoglobulin 5g/L (BLG5), skim milk proteins (MP). 

The six major proteins of milk, asl-, o s2-, and /c-casein, jS-lactoglobulin, and a-lactalbumin, contain at least one tryptophan residue [57], the fluorescence of which allows the monitoring of the structural modifications of proteins and their physicochemical environment during the coagulation processes. Emission fluorescence spectra of the protein tryptophanyl residues were recorded for the milk coagulation kinetics induced by... 

This chapter has reviewed the application of ROA to studies of unfolded proteins, an area of much current interest central to fundamental protein science and also to practical problems in areas as diverse as medicine and food science. Because the many discrete structure-sensitive bands present in protein ROA spectra, the technique provides a fresh perspective on the structure and behavior of unfolded proteins, and of unfolded sequences in proteins such as A-gliadin and prions which contain distinct structured and unstructured domains. It also provides new insight into the complexity of order in molten globule and reduced protein states, and of the more mobile sequences in fully folded proteins such as /1-lactoglobulin. With the promise of commercial ROA instruments becoming available in the near future, ROA should find many applications in protein science. Since many gene sequences code for natively unfolded proteins in addition to those coding for proteins with well-defined tertiary folds, both of which are equally accessible to ROA studies, ROA should find wide application in structural proteomics. 

Whey contains 1.5 kg/m3 of lactalbumin and 3.0 kg/m3 of lactoglobulin. At 85 °C the following data are available on the kinetics of protein degradation, using initial concentrations that are the same as those in whey. 

---