Effect of isoelectric focusing on the amino-acid composition of proteins

The Analyst ◽  
1973 ◽  
Vol 98 (1162) ◽  
pp. 25 ◽  
Author(s):  
S. Jacobs
Keyword(s):  
Amino Acid ◽  
Amino Acid Composition ◽  
Acid Composition ◽  
Isoelectric Focusing

scholarly journals Studies on Ovalbumin V. The Amino Acid Composition and Some Properties of Chicken, Duck, and Turkey Ovalbumins

1970 ◽  
Vol 23 (5) ◽  
pp. 1221 ◽  
Author(s):  
MB SmIth ◽  
Joan F Back
Keyword(s):  
Amino Acid ◽  
Amino Acid Composition ◽  
Ammonium Sulphate ◽  
Acid Composition ◽  
Isoelectric Focusing ◽  
Ph Gradient ◽  
Ammonium Sulphate Fractionation

The ovalbumins from chicken, duck, and turkey eggs were prepared by ammonium sulphate fractionation and purified by isoelectric focusing in a pH gradient from 3 to 6. Amino acid analyses show a closer relationship between turkey and chicken ovalbumins than between duck and chicken ovalbumins.

Isoelectric focusing electrophoresis of protein-ligand conjugates: effect of the degree of substitution

1991 ◽  
Vol 37 (1) ◽  
pp. 87-90 ◽  
Author(s):  
Mlnas S Barbarakis ◽  
Leonldas G Bachas
Keyword(s):  
Amino Acid ◽  
Theoretical Model ◽  
Amino Acid Composition ◽  
Acid Composition ◽  
Isoelectric Focusing ◽  
Isoelectric Point ◽  
Calibration Curve ◽  
Degree Of Substitution

Abstract The degree of substitution of protein-ligand conjugates can be determined from the change of the isoelectric point (pI) of the protein when ligand molecules are attached to its surface. Specifically, the pI values of conjugates with known degrees of substitution are obtained by isoelectric focusing electrophoresis and are used to generate a calibration curve that relates these two variables. The shape of the curve is sigmoidal and can be predicted by a theoretical model that takes into account the degree of substitution and the amino acid composition of the protein. By using such a calibration curve, one may estimate the degree of substitution of a given protein-ligand conjugate from its pI value. The applicability of the method is demonstrated with conjugates of pyridoxal 5-phosphate and avidin.

scholarly journals α1-Acute-phase globulins of rats. Microheterogeneity after isoelectric focusing

1972 ◽  
Vol 130 (1) ◽  
pp. 95-101 ◽  
Author(s):  
A. H. Gordon ◽  
P. J. Dykes
Keyword(s):  
Sialic Acid ◽  
Amino Acid ◽  
Amino Acid Composition ◽  
Acid Composition ◽  
Isoelectric Focusing ◽  
Isoelectric Points ◽  
Individual Bands ◽  
The Stability ◽  
The Individual ◽  
Gel Isoelectric Focusing

1. Improved resolution of mixtures of α1-globulins was obtained by the use of isoelectric focusing. 2. Because material recovered after isoelectric focusing in polyacrylamide gels behaved in a manner which suggested interaction with components derived from the gel, isoelectric focusing when used for preparative purposes was done in a matrix of Sephadex G-75. 3. By this means material from the individual bands formed by isoelectric focusing in 6m-urea could be isolated. The stability of these substances was examined by further isoelectric focusing. 4. Analysis of material that had been shown to be homogenous by isoelectric focusing in the absence of urea and of that from several individual bands derived from the same sample by isoelectric focusing in 6m-urea showed different proportions of sialic acid but no change in amino acid composition. 5. In the presence of 6m-urea the isoelectric points found were increased by 0.14–0.25 pH unit. After removal of most of the sialic acid with neuraminidase the increase was 0.36–0.72 pH unit. After treatment with 0.025m-H2SO4 at 80°C for 1h, which removed all the sialic acid, the increase was 0.40–0.87 pH unit. 6. Because removal of all the sialic acid did not decrease the number of bands formed by isoelectric focusing the observed heterogeneity could not be caused entirely by the presence of various proportions of sialic acid.

scholarly journals Mapping and biochemical analysis of Hor 4 (Hrd G), a second locus encoding B hordein seed proteins in barley (Hordeum vulgare L.)

1988 ◽  
Vol 51 (1) ◽  
pp. 5-12 ◽  
Author(s):  
Peter R. Shewry ◽  
Saroj Parmar ◽  
Julian Franklin ◽  
Rodger White
Keyword(s):  
Amino Acid ◽  
Hordeum Vulgare ◽  
Genetic Analysis ◽  
Amino Acid Composition ◽  
Acid Composition ◽  
Isoelectric Focusing ◽  
Biochemical Analysis ◽  
Seed Proteins ◽  
Chromosome 5 ◽  
Hordeum Vulgare L

SummaryThe hordein polypeptide controlled by the Hrd G (Hor 4) locus in Elgina and derived lines was purified by preparative isoelectric focusing. The amino acid composition was similar to those of the major B hordeins encoded by the Hor 2 locus. Genetic analysis confirmed that Hor 4 is located proximally to Hor 1 on the short arm of chromosome 5. It is speculated that Hor 4 arose by translocation of genes from Hor 2, possibly in an ancestor of Elgina.

Structural study on liver gelactin

1984 ◽  
Vol 62 (11) ◽  
pp. 1072-1075 ◽  
Author(s):  
Julian Gruda ◽  
Hélène-Marie Thérien
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Amino Acid ◽  
Amino Acid Composition ◽  
Acid Composition ◽  
Structural Study ◽  
Isoelectric Focusing ◽  
Isoelectric Point ◽  
Gel Filtration ◽  
Rabbit Liver

Electron microscopy, ultracentrifugation, gel filtration, and isoelectric focusing were carried out with gelactin, an actin-gelling protein from rabbit liver. Gelactin is a dimeric acidic protein (isoelectric point (pI) = 5.45), with a molecular weight of 190 000, a Svedberg constant of 6.25, and a Stoke's radius and length of 7.0 and 28 nm, respectively. While different from α-actinin by pI and amino acid composition, gelactin belongs by its dimensions to the class of α-actinins.

Subunit structure of the 12S protein from seeds of Brassica juncea

1975 ◽  
Vol 53 (24) ◽  
pp. 2901-2907 ◽  
Author(s):  
S. L. MacKenzie
Keyword(s):  
Amino Acid ◽  
Amino Acid Composition ◽  
Brassica Juncea ◽  
Acid Composition ◽  
Isoelectric Focusing ◽  
Electrophoretic Analysis ◽  
Subunit Structure ◽  
Isoelectric Points

The 12S globulin from Brassica juncea seeds has been dissociated by 6 M urea: 0.1 M mercaptoethanol and the resultant products have been partially separated by preparative isoelectric focusing. Species that have the isoelectric points 4.75, 5.15, 5.40, 6.25, 6.70, 7.00, 7.20, 7.70, 8.30, 8.90, and 9.15 were detected. The results of poly aery lamide-gel electrophoretic analysis and the amino acid composition of the fractions suggested that the isoelectric species were distinct subunits.

scholarly journals Studies on the structure of sphingomyelinase. Amino acid composition and heterogeneity on isoelectric focusing

1983 ◽  
Vol 209 (2) ◽  
pp. 291-297 ◽  
Author(s):  
C S Jones ◽  
P Shankaran ◽  
D J Davidson ◽  
A Poulos ◽  
J W Callahan
Keyword(s):  
Amino Acid ◽  
Amino Acid Composition ◽  
Acid Composition ◽  
Isoelectric Focusing ◽  
Protein Profile ◽  
Minor Component ◽  
Intact Protein ◽  
Amino Acid Residues ◽  
Apparent Homogeneity ◽  
A Minor

Sphingomyelinase, purified to apparent homogeneity from human placenta, is an acidic protein, as judged from its amino acid composition and by isoelectric focusing of the carboxymethylated protein. The amino acid composition is characterized by an approximately equal content of hydrophobic and polar amino acid residues. The reduced-alkylated polypeptides were separated into two groups. Most of the polypeptides were heterogeneous with pI values of 4.4-5.0, but an additional more minor component was observed at pI 5.4. Liquid isoelectric focusing resolved the purified enzyme into a single major component (pI 4.7-4.8), a minor component (pI 5.0-5.4) and a plateau region of activity (pI 6-7). On thin-layer isoelectric focusing, the protein profile obtained from each of these regions was the same. In addition, the substrate specificity, Km values and effect of inhibitory substances were identical. We conclude that sphingomyelinase is an acidic, microheterogeneous protein that likely exists as a holopolymer of a single major polypeptide chain. the heterogeneity of the intact protein on isoelectric focusing appears to reflect this microheterogeneity, which is influenced by a tendency to associate with itself and with detergents such as Triton X-100.

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