Lacto globulin

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...

Figure 5.27 Selective detection of lactolated peptides from a tryptic digest of / -lacto-globulins by LC-electrospray-MS-MS, showing (a) the total-ion-cnrrent trace in full-scan mode, and (b) the total-ion-current trace in neutral-loss-scanning mode. Figure from Selective detection of lactolated peptides in hydrolysates by liquid chromatography/ electrospray tandem mass spectrometry , by Molle, D., Morgan, F., BouhaUab, S. and Leonil, J., in Analytical Biochemistry, Volume 259, 152-161, Copyright 1998, Elsevier Science (USA), reproduced with permission from the publisher.

Over the temperature range of interest, the activation energy for the lactalbumin degradation reaction is 25.1 kJ/mole while that for the lacto-globulin degradation reaction is 121 kJ/mole. 

Substrate Peanut Arachin gg Albumin Bovine Serum Albumin Bovine Hemoglobin B-Lacto- globulin Wheat Gliadin Yam Protein... 

Remondetto, G.E., Subirade, M. (2003). Molecular mechanisms of Fe2+-induced p-lacto-globulin cold gelation an interactions story. Biopolymers, 69, 461 169. 

Girard, M., Turgeon, S.L., Gauthier, S.F. (2003). Thermodynamic parameters of p-lacto-globulin-pectin complexes as assessed by isothermal titration calorimetiy. Journal of Agricultural andFood Chemistry, 51, 4450 1455. 

Ayniard, P., Nicolai, T., Durand, D. (1999). Static and dynamic scattering of p-lacto-globulin aggregates formed after heat-induced denaturation at pH 2. Macromolecules, 35, 2542-2552. 

Gezimati, J., Creamer, L., Singh, H. (1997). Heat-induced interactions and gelation of mixtures of p-lacto globulin and a-lactalbumin. Journal of Agricultural and Food Chemistry, 45, 1130-1136. 

Olsson, C., Langton, M., Hermansson, A.-M. (2002). Dynamic measurements of p-lacto-globulin structures during aggregation, gel formation and gel break-up in mixed biopolymer systems. Food Hydrocolloids, 16, 477 188. 

Dickinson, E., Hong, S.-T. (1997). Influence of an anionic surfactant on the rheology of heat-set p-lacto globulin-stabilized emulsion gels. Colloids and Surfaces A Physicochemical and Engineering Aspects, 127, 1-10. 

Parkinson, E.L., Dickinson, E. (2004). Inhibition of heat-induced aggregation of a p-lacto-globulin-stabilized emulsion by very small additions of casein. Colloids and Surfaces B Biointerfaces, 39, 23-30. 

Figure 1. Light-scattering data on p-lacto globulin A in various concentrations of 2-chloroethanol at constant chemical potential of 2-chloroethanol...

During the nineteenth and early twentieth centuries, separation of the proteins was limited to casein and the classical lactalbumin and lacto-globulin fractions of the whey proteins. Subsequent work has resulted in the identification and characterization of numerous proteins from each of these fractions. A classification system of the known proteins in milk developed by the American Dairy Science Association s (ADSA) Committee on Milk Protein Nomenclature, Classification, and Methodology (Eigel et al 1984) is summarized and enlarged to include the minor proteins and enzymes in Table 3.1. 

Green, D. W. 1964. Cited by S.N. Timasheff and R. Townend. Structure of the, 3-lacto-globulin tetramer. Nature 203, 517-519. 

Lactoglobulin With a denaturation temperature of 78°C, /3-lacto-globulin is the least denaturable of the serum proteins (Table 11.2). It exhibits a second thermal change near 140°C caused by a breakdown of disulfide bonds and additional unfolding of the molecule (de Wit 1981 Watanabe and Klostermeyer 1976). A change in pH between 6 and 7.5 shifts denaturation between 78° and 140°C, the total denaturation at the two temperatures being nearly constant. pH 6 favors dena-... 

Elfagm, A. A. and Wheelock, J. V. 1977. Effect of heat on a-lactalbumin and /3-lacto-globulin in bovine milk. J. Dairy Res. 44, 367-371. 

Morr, C. V., Van Winkle, Q. and Gould, I. A. 1962. Application of polarization of fluorescence technique to protein studies. III. The interaction of x-casein and (3-lacto-globulin. J. Dairy Sci. 45, 823-826. 

Zittle, C. A., Thompson, M. P., Custer, J. H. and Cerbulis, H. 1962. x-Casein-/3-lacto-globulin interaction in solution when heated. J. Dairy Sci. 45, 807-810. 

Vittayanont, M., Steffe, J.F., Flegler, S.L., and Smith, D.M. 2003. Gelation of chicken pector-alis major myosin and heat-denatured (J-lacto-globulin. J. Agric. Food Chem. 51 760-765. 

Mackie, A. R., Mingins, J., Dann, R., and North, A. N. (1991). Preliminary studies of pS-lacto-globulin adsorbed on polystyrene latex. In Food Polymers, Gels and Colloids, Dickinson, E. (Ed.), pp. 96-112. Royal Chem. Soc., London. 

Nagasawa, K., Takhashi, K., and Hattori, M. 1996. Improved emulsifying properties of (3-lacto-globulin by conjugating with carboxymethyl dextran. Food Hydrocoll. 10, 63-67. 

Heat Treatment of Milk Containing 14C-Metbyl-Labeled K-Casein or ft-Lacto globulin as Tracers... 

Protein Composition of Milk. Skim milk is a colloidal suspension of extreme complexity. The particulate phase, the casein micelles, consists primarily of a mixture of asi, as2, / , and x-caseins combined with calcium ions and an amorphous calcium-phosphate-citrate complex. The soluble phase contains lactose, a fraction of the caseins and calcium, and, in raw milk, the whey proteins, which are predominantly /3-lacto-globulin and a-lactalbumin. When milk is centrifuged at high speed (in our experiments, 30 min at 110,000 X gravity), the casein micelles sediment. This permits one to separate the two physical phases of skim milk and to measure changes in composition of the phases resulting from... 

Effect of Forewarming and Concentration on 14C-Methyl-/ -Lacto-globulin Distribution in Milk. The stability of milk that is to be concentrated before sterilization is improved by a preliminary heat treatment (forewarming), but concentrated milk may be destabilized by the same heat treatment. An interaction of serum proteins with x-casein may be involved more detail is available in a recent review on the heat stability of milk (17). 

With several other proteins, such as bovine serum albiunin (Tanford and Roberts, 1952), lysozyme (Tanford and Wagner, 1954), and/3-lacto-globulin (Tanford and Swanson, 1957), pK shifts of the phenolic OH groups of tyrosine residues are observed, but these are of a qualitatively different nature. Thus, the tyrosines of any one of these proteins cannot be readily differentiated into a normal and an abnormal variety, since the spectrophotometric titration data for these proteins are reversible and fall on single smooth curves, in contrast to the situation with RNase. On the other hand, the tyrosine residues of ovalbumin show comparable behavior to the three abnormal tyrosine groups of RNase (Crammer and Neuberger, 1943). About 2 of the total of 9 tyrosine residues appear to titrate normally, but the remainder are not titrated up to pH 12. At pH 13, these anomalous tyrosines become titratable, and this is accompanied by the irreversible denaturation of the ovalbumin molecule. 

It is seen from the discussion of the data for ribonuclease and /3-lacto-globulin (Figs. 13 and 14) that two simple factors can lead to w values which are less than those given in Table III, but only by a small amount. There is imcertainty in the choice of a radius for the sphere used to represent the molecule, and experimental uncertainty as to the relation between 2 and Zh. The uncertainty in the radius can account only for smaller values of w than those of Table III, because the values in the table are based on what is essentially the minimum possible radius. The uncertainty in Z can accoimt only for smaller values of w (if Zn is used as abscissa in the logarithmic plots) because any change in Zh will favor the binding of oppositely charged ions, so that increments in Z are less than those in Zh. ... 

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