Comparison of manual methods of determination of albumin in human cerebrospinal fluid by the bromcresol green and immuno-precipitation methods

Simultaneous determinations of albumin concentrations in human cerebrospinal fluid were made by three different manual methods: bromcresol green dye-binding technique of Doumas et al., a modification of the latter with color measurement shortly after the addition of dye as proposed by Ingwersen and Raabo and finally by an immuno-precipitation technique. Results obtained by the immuno-precipitation method correlated significantly with the dye-binding method of Doumas et al., (r = 0.93) and the procedure of Ingmersen and Raabo (r = 0.94). Data from the two dye-binding techniques correlated significantly with one another also (r = 0.98). However, the immuno-precipitation technique gives albumin values lower than the dye-binding procedures. The latter presumably estimates other proteins which can also bind bromcresol green. The data corroborates the conclusions of earlier investigators that immuno-precipitation method is more specific for albumin assays.

Functional abnormality of proalbumin Christchurch

Proalbumin Christchurch is a varient of human albumin in which the C-terminal basic residue of the propeptide has undergone a mutation to glutamine. In this investigation spectral and equilibrium dialysis studies have shown that the variant lacks the high affinity copper binding site of normal albumin. A simple electrophoretic procedure is described using 63Ni(II), which allow discrimination of proalbumins from other variants of albumin. The finding that Proalbumin Christchurch is readily cleaved in vitro by trypsin but is secreted uncleaved in vivo is evidence that propeptide cleavage is due to specific proteolysis with paired basic residues being a pre-requisite.

A highly reactive tyrosine residue as part of the indole and benzodiazepine binding site of human serum albumin

The interaction of L-tryptophan and four benzodiazepine derivatives with tyrosine-modified human serum albumin was investigated by equilibrium dialysis and circular dichroism measurements. Out of the 18 tyrosine residues of the human serum albumin molecule, only 9 could be modified with tetranitromethane. At least up to a degree of modification of 5, the conformation of human serum albumin was not changed and no crosslinking and fractionation has been found, as revealed from circular dichroism measurements in the far ultraviolet range and from SDS polyacrylamide electrophoresis. The modification of only 2 out of the 9 accessible tyrosine residues of human serum albumin strongly affects the binding of L-tryptophan and diazepam to their common, stereospecific bindining site. This was evidently shown by a reduction of the association constants by more than 90% and by a large reduction of the extrinsic Cotton effects of four benzodiazepines bound to human serum albumin. The numbers of binding sites remained unchanged. Strong evidence was presented that only one tyrosine residue, which reacts faster with tetranitromethane than all others, is mainly involved in the specific indole and benzodiazepine binding site of human serum albumin. The location of this highly reactive tyrosine residue and that of the specific indole and benzodiazepine binding site within the human serum albumin primary structure is discussed.

Chemical characterization of human urine albumin in proteinuria

From the urine of a patient with proteinuria, the albumin protein component was isolated and compared with human serum albumin. By comparing the amino acid composition of the original proteins and their large cyanogen bromide fragments, peptide maps and N-terminal sequences of 33 amino acid residues, the identity of both proteins was shown.

Activity coefficients of salts in highly concentrated protein solutions. I. Alkali chlorides in isoionic bovine serum albumin solutions

In order to understand the thermodynamic state of simple salts in living cells, the mean activity coefficients of LiCl, NaCl, KCl, RbCl, CsCl were determined in concentrated isoionic bovine serum albumin (BSA) solutions by use of the EMF method with ion exchange membrane electrodes. The protein concentration range extended up to 22 wt%, whereas the salt concentration was kept constant at 0.1 mole per kilogram water. These solutions may be regarded as crude but appropriate model systems for the cytoplasm of cells as far as type and magnitude of the macromolecular component influence on the chemical potential of the salts is concerned. The mean stoichiometric activity coefficients of the alkali chlorides in the isoionic BSA solutions decreased linearly with the protein molality; this decrease, however, did not exceed ca. 10% compared with the pure 0.1 molal salt solutions. Only very small differences in the behavior of the different alkali chlorides were observed. The results may be interpreted by the superposition of the effects of specific Cl- ion binding to BSA and BSA bound "non-solvent" water with probably electrostatic long range interactions of the BSA(Cl-)nu polyions with the salt ions in solution. The resulting mean activity coefficients, corrected for ion binding and non-solvent water, showed a very slight linear dependence on the protein concentration. The departure from the value in the pure 0.1 molal salt solutions did not exceed +/- 2%.

Electrophoretic bimorphism of serum albumin in the presence of indocyanine green

The presence of indocyanine green during extended traditional electrophoresis and immunoelectrophoresis of serum is associated with bimorphism of albumin. This occurs over a range of dye--albumin molar ratios an order or more greater than was obtained in similar phenomena described previously. The bimorphism seems not to be dose dependent beyond a certain point, and the two albumins so separated show tinctorial differences. The phenomenon has been observed to apparently the same degree in all normal sera tested, and may represent a means of distinguishing ligand-loaded and ligand-light serum albumin.

The synthesis and secretion of serum albumin in Morris hepatomas 5123tc and 9121

In vivo, Morris hepatomas 5123tc and 9121 do not secrete serum proteins into the bloodstream. However, they synthesize albumin, at a reduced rate, if compared with liver. The produced albumin accumulates, leading to an enlargement of the Golgi apparatus and the appearance of intracellular vesicles. The proportion and the absolute amount of albumin found within the hepatoma cells is increased compared with liver. As described recently for liver in vivo and for hepatocyte suspensions, albumin is synthesized also in hepatoma cells via a precursor protein. Hepatoma cells in culture secrete albumin into the medium. However, albumin accumulates in the cells with time in culture, indicating again a limited secretory capacity of the hepatoma cell.