Microheterogeneity of albumin

Rg.1 Detection of microheterogeneity of albumin chicken egg by capillary zone electrophoresis. Capillary, bare fused-silica (50 jum X 37 cm, 30 cm to the detector) electrolyte solution, 25 mM Tris-glycine buffer containing 0.5% (v/v) Tween-20 and 2.0 mM putres-cine applied voltage, 20 kV UV detection at the cathodic end. 

It is not apparent whether the differences in the sequence of HSA reported by the two groups were the outcome of microheterogeneity, which was often demonstrated, or whether they were due to experimental errors. At the moment, the only strong evidence for microheterogeneity of albumin as a result of the primary structure comes from the work by Lapresle and Doyen (1975), who showed, by cyanogen bromide cleavage of HSA, that about 16% of the molecules lacked methionine at position 123. 

Bhargava, H. N. and Foster, J. F. 1970. Reversible boundary spreading as a criterion of microheterogeneity of plasma albumins. Biochemistry 9, 1977-1983. 

Carry out the first dimension electrophoresis with 10 V/cm in the gel (controlled with the voltmeter). It ukes 80 min for the colored bovine albumin to cross the plate. This electrophoresis time was convenient in our studies of the microheterogeneity of human serum Oj-antichymotrypsin see Note 5). 

E. Valmet, The microheterogenity of human serum albumin. Protidea Biol. Fluids, Brugge, 1969a. 

In 1954 Colvin, Smith, and Cook advanced the concept of microheterogeneity of proteins. They concluded that a native protein should be described as a population of closely related individiuals which may differ either discretely or continuously in a number of properties and cited plasma albumin as an example. 

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),... 

From this, as well as from the other physical studies, Foster et al. concluded that while the pH-dependent IV - F transformation is rapidly and completely reversible, at intermediate pH values, bovine plasma albumin consists of stable noninterconvertible N and F isomers. To explain this apparent contradiction, they proposed the microheterogeneity model for plasma albumin. This model postulates the... 

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