S-Lactoglobulin

Table 5.7 Theoretically predicted polypeptides from the trypsin digestion of / -lacto-globulin (/il.G)". 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 /S-lactoglobulin , 91-103, Copyright (1997), with permission from Elsevier Science...

Slade and Vulfson have shown that the catalytic activity of native BSA in the dehydrofluorination reaction in aqueous media is greater than that reported for catalytic antibodies and molecularly imprinted polymers [30]. These authors therefore imprinted ]S-lactoglobulin and papain using A-isopropyl-4-nitrobenzyl amine as the transition state analogue. The catalytic activity of the imprinted proteins was evaluated in the dehydrofluorination reaction using acetonitrile as the reaction medium. A three fold rate enhancement in the A eat value vis-d-vis non-imprinted proteins was observed. 

Dickinson, E. and Yamamoto, Y. 1996b. Effect of lecithin on the viscoelastic properties of /S-lactoglobulin-stabilized emulsion gels. Food HydrocoUids 10 301-307. 

An interesting example which capitalizes on the ability of the hydro-phobic cavity of (3-lactoglobulin to carry a hydrophobic molecules and complexation has been recently reported (Zimet and Livney, 2009). It was found that (S-lactoglobulin binds docosahexaenoic acid (DHA) and further that DHA-loaded (S-lactoglobulin can form nanocomplexes ( 100 nm) with low methoxy pectin at a pH colloidal stability and protected DHA against oxidation. 

D B-lactoglobulin B E S-lactoglobulin A. Reproduced with permission from Ref. 22. Copyright 1986 Trends Anal. Chem. 

Table I. Amino Acid Composition of Bovine )S-Lactoglobulin as Determined by Different Procedures"...

The spectra of other genetic variants, )S-lactoglobulins B and C, were also found by TimashdT and Susi (1966) to be identical with the data for lactoglobulin A, suggesting very similar secondary structures. 

Susi et al. (1967) have observed spectra of poly-L-lysine, poly-L-glutamic acid, )S-lactoglobulin, myoglobin, and a -casein in the region of absorption of the amide I band in HjO and DjO solutions, and in the solid state. Their results indicated that characteristic frequencies exhibited by specific conformations of the synthetic polypeptides studied are not transferable to corresponding conformations of globular proteins. 

Whey proteins are consisted of ]S-lactoglobulin, a-lactalbumin, proteose peptone, serum albumin, immunoglobulins and lactoferrin. In contrast with caseins, they are... 

Figure 2 shows ti-A isotherms for spread films of BSA and j8-lactoglobulin at the A-W interface and at the O-W interface. The size of the symbol may be taken as the magnitude of the error in the measurement of the quantity on the ordinate axis in this figure (and also in the other figures in this paper). For BSA the aqueous phase was pH 7.4, 0.3 M NaCl, for comparison with the result of Mac-Ritchie [8], obtained under the same conditions. For )S-lactoglobulin the aqueous phase was 0.02 mol dm imidazole buffer, adjusted to pH 7.0 with HCl. The relative molecular mass of BSA was taken as 66 500 Da [9] and that of j8-lactoglobuIin (dimeric form) taken as 36 700 Da [10] for calculation of the ti-A isotherms. 

The above experiments on monolayers illustrate the strong dependence of desorption rates on n. In real systems stabilised by proteins, n for the film on average does not exceed a particular maximum value at which the rate of adsorption from solution is balanced by the rate of desorption. On perturbation from the equilibrium state of the film, such as a transient (local) expansion or compression a knowledge of both rates is important. Unfortunately, measurements of adsorption rates are not so straightforward since the surface concentration of protein, r, must be monitored with time and is not predetermined as in the spread monolayers. There is often disagreement between adsorption kinetic results obtained via different techniques - see below, for example. Relatively few measurements have been made of the adsorption kinetics of S-lactoglobulin at the A-W interface and for all proteins, because of experimental difficulties, there seem to be almost no direct measurements of r t) at O-W interfaces. 

---