Bovine serum albumin heterogeneity

Hunter, A.K. and Carta, G. 2001. Effects of bovine serum albumin heterogeneity on frontal analysis with anion-exchange media. J Chromatogr A 937(1-2) 13-19. 

Bovine Serum Albumin. Since Polis et al. (1950) crystallized bovine serum albumin from whey and demonstrated that it was identical in all properties investigated to blood serum albumin, except in its electrophoretic behavior at pH 4.0, very little work has been done on this protein as isolated from milk. However, much work has been done on the protein isolated from bovine blood plasma. There is considerable evidence that serum albumin is heterogeneous. For example, Spencer and King (1971) have demonstrated several protein bands by electrophoretic focusing, with two major isoelectric components differing by one unit of charge. The chemical nature of this difference is not known. 

The configuration of bovine serum albumin isolated from milk has not been investigated, but extensive investigations of this protein isolated from bovine blood serum have been made. The protein exhibits at least three different kinds of heterogeneity (1) due to polymer formation, (2) related to the sulfur linkages in the molecule, and (3) microheterogeneity. Fractionation of bovine serum albumin on DEAE-Sephadex A-50 resulted in a monomer and two dimer fractions (Janatova et al. 1968),... 

Due possibly to the above mentioned heterogeneity, there is some variability with regard to the conclusions reached by various workers concerning the structure and configuration of bovine serum albumin. Brown (1977) proposed two possible models based on the primary sequence of the protein. He demonstrated that the molecule could possess a triple domain structure with three very similar domains residues 1-190, 191-382, and 383-582. Each domain could then consist of five helical rods of about equal length arranged either in a parallel or an antiparallel manner. His second model consisted of the following (1) a lone subdomain (1-101) (2) a pair of antiparallel subdomains, with their hydrophobic faces toward each other (113-287) (3) another pair of subdomains (314-484) and (4) a lone subdomain (512-582). These structures are supported by the observed helical content of bovine... 

The molecular-sieving effect on proteins has been very clearly demonstrated by Pedersen (1962). Bovine serum albumin, obtained by fractionated ammonium sulfate precipitation, was filtered through a column of cross-linked dextran of water regain 15 gm/gm (Sephadex G-200). Monomer and dimer forms were easily separated from each other and from other components of larger sedimentation constants (Fig. 8). Heterogeneity in the monomer as well as in the dimer preparation was indicated... 

Besides the conventional factors causing peak broadening in LC. another source for lower efficiency in LC with chiral stationary phases may be the existence of at least two different adsorption sites (the stereoselective and non-stereoselective ones) that may considerably differ in their adsorption kinetics (heterogeneous mass transfer kinetics) and thus cause peak broadening and tailing. These factors have been investigated and modelled by Fomstedt et al.. e.g. for protein type CSPs [75,91-9.3] and their contribution was determined for different analytes and different type of CSPs (bovine serum albumin, cellobiohydrolase 1, tris(4-methylbenzoyl) cellulose) [94j. In a recent study, these authors reported on the adsorption isotherms as well as selective and nonselective contributions of propranolol enantiomers on a cellobiohydrolase 1 CSP in dependence of the mobile phase pH [95[. 

Bovine serum albumin (Spencer and King, 1971 Salaman and Williamson, 1971 Wallevik, 1973, 1976) or human serum albumin (Ui, 1971) showed two or three major components in isoelectric focusing. The fact that heterogeneity persisted in defatted BSA after reversible denaturation in 6 M guanidine HCl or 6 M urea eliminated bound ligands as the only cause of heterogeneity. Also, the finding that serum albumin from six... 

Many enzyme immobilization techniques developed in connection with the preparation of heterogeneous biocatalysts have been applied for the construction of enzyme electrodes as well as for other types of biosensors. The immobilization of enzymes or other biocomponents on different membranes is most frequently realized by crosslinking agents, first of all by glutaraldehyde, and with the addition of bovine serum albumin [169] or other proteins, with l,8-diamino-4-aminomethyloc-tane, [170], etc. 

In addition to varying the substrates, other authors have worked on the conditions in order to extend the scope of the reaction. In particular, MW [127] and ultrasound [128] irradiations have been applied successfully, decreasing considerably the reactions times. On the other hand, different catalysts have been used substituting the classical secondary or tertiary amines [129], for example, L-proline [130], imidazole [131], cesium carbonate (Cs COj) [132], amine-functional polysiloxanes (AFPs) [133], MgAa mixed oxide as a heterogeneous solid base catalyst [134], ZnO (under solvent-free conditions) [135], bovine serum albumin (BSA) [136], and guanidine-based IL [137]. 

Additional whey proteins, including P-lactoglobulin and bovine serum albumins, are also allergenic. Bovine serum albumin (67 kDa) comprises approximately 1 % of total milk protein and is quite heterogeneous in nature, with several different isoforms. 

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