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Structural studies on chicken IgG immunoglobulin

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Title:Structural studies on chicken IgG immunoglobulin
Authors:Kubo, Ralph Teruo, 1942
Date Issued:1970
Abstract:Chicken IgG L chains have a molecular weight of 23,700±800 daltons, and chicken IgG H chains have a molecular weight of 60,800±1400 daltons as determined by high speed sedimentation equilibrium. The sum of the masses of two L chains and two H chains are in excellent agreement with the molecular weight reported for chicken IgG (170,000 daltons). The number of disulfide bonds reduced per molecule of IgG was determined at various concentrations of ME by a titration method. The reduced samples were also analyzed by gel filtration at pH 8.2 and at pH 2.4. A sample of IgG was reduced with 0.01 M ME. About 1.3 disulfide bonds per molecule were reduced. Gel filtration at pH 8.2 showed that no dissociation of the reduced IgG occurred, while by gel filtration at pH 2.4 a relative yield of 4.3% free L chains was obtained. Reduction of chicken IgG with 0.05 to 0.2 MME resulted in the release of free L chains at pH 8.2. Reduction with 0.05 M ME and 0.2 MME reduced 3-4 and 6-7 disulfide bonds per molecule respectively. The gel filtration patterns at pH 2.4 of chicken and human IgG each reduced with 0.01 M ME were similar. Free L chain material was detected in the elution patterns of the two reduced samples. Rabbit IgG was reduced with 0.01 MME and gel filtered at pH 2.4. The elution patterns indicate that most of the IgG were converted to half molecules; no free L chains could be detected. It was concluded that the disulfide bonds between the L and H chains of chicken IgG are more easily reduced than the inter- H chain disulfide bonds. Papain cleaved chicken 19G into Fab and Fc fragments and smaller peptides. The Fab fragment had a molecular weight of 55,300 daltons. The Fc fragment had a molecular weight of 56,900 daltons and was crystallizable. Digestion of chicken 19G with pepsin at pH 4.5 resulted in the conversion to 3.5 S material generally. Small amounts of 5.5 S material (F(ab ' )2) was isolated from pepsin digested chicken 19G euglobulins at pH 4.5 and from 19G pseudoglobulin digested at pH 5.0. The 3.5 S material from five-hour digests contained both Fab' and Fc-like components. After 18 hours of digestion, only 3.5 S Fab' fragments were detected. The yields of various fragments from pepsin digested chicken 19G were dependent upon the digestion time, pH, and type of 19G preparation. Undigested 19G, Fab-like and Fc-like fragments were detected in tryptic digests of chicken 19G at pH 7.2. By ultracentrifugation, 7 S, 5 S, and 3.5 S material were observed. The 5 S material was not isolated. The effect of high salt (1.5 M NaCl) on the aggregation of chicken Fab, Fc, and F(ab')2 was investigated. The Fab and F(ab')2 were not affected by salt concentration with respect to aggregation, while the Fc fragment was completely precipitated in high salt. The relationship on the salt-induced phenomenon to the dependence of high salt of the chicken precipitin reaction was discussed and a hypothetical model for this relationship was presented. Peptide maps of chicken Fab, Fc, H chains, and L chains were prepared. Chicken Hand L chains appear to possess the same variability with regard to heterogeneity as rabbit Hand L chains, respectively. Most of the chicken H chains (60-80%) possessed alanine as the amino-terminal residue. Only 6% of the L chains had alanine at the amino-terminal position. No other amino acids were detected at the amino-terminus.
Thesis (Ph. D.)--University of Hawaii, 1970.
Bibliography: leaves [192]-202.
x, 202, [1] l illus., graphs, tables
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: Ph.D. - Microbiology

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