Human milk K-casein was isolated from the acid-precipitated casein fraction on Sephadex G-200 and Mono Q HPLC. Samples of K-casein purified from different donors were found similar in both amino acid and carbohydrate composition. A molar extinction coefficient of 11.2 was determined on the basis of amino acid analysis with a norleucine internal standard. Tracer K-casein for human micelle studies was 3H-labeled in the sialic acid moiety of its carbohydrate. The human micelle system was investigated in its native form at 37°C. Micelle reformation by re-equilibration in skimmed milk at 4°C (overnight) followed by 3 h at 37°C was studied with and without the labeled K-casein tracer. After the micelles were fractionated by ultracentrifugation into sized pellets, the mole ratio of K/p-casein was determined by reverse phase HPLC and the six forms of phosphorylated p-casein were quantitated by anion exchange HPLC. In all systems, the relative amount of K-casein increased inversely with the micelle size, suggesting a surface location for K-casein in the micelles.
Support for the surface location also came from the reequilibrated 3H-K-casein micelle study, where the labeled K-casein increased linearly with the micelle surface area/volume ratio. Of the p-caseins, 0-P and 1-P showed greatest variability with micelle size. The proportion of 0-P within the (3-casein fraction decreased with decreasing micelle size but to a greater extent in the re-equilibrated system compared with the native. This indicates that the lack of ability to form Ca++ ion bridges permitted 0-P p-casein to dissociate at low temperatures but hampered reassociation at 37°C. These observations suggest the biosynthetic process is not as simple as component p-Casein with 1-P appeared to increase as the micelle surface area increased. aggregation from whey solution. supporting a surface position for 1-P and its potential to stabilize micelles against precipitation by Ca++. Collectively these findings support a surface position for K-casein in agreement with the Slattery-Evard model for bovine milk micelles. However, the presence of p-caseins with different properties, due to levels of phosphorylation, makes the human micelle more complex.
","abstract_html":"<p>Human milk K-casein was isolated from the acid-precipitated casein fraction on Sephadex G-200 and Mono Q HPLC. Samples of K-casein purified from different donors were found similar in both amino acid and carbohydrate composition. A molar extinction coefficient of 11.2 was determined on the basis of amino acid analysis with a norleucine internal standard. Tracer K-casein for human micelle studies was <sup>3</sup>H-labeled in the sialic acid moiety of its carbohydrate. The human micelle system was investigated in its native form at 37°C. Micelle reformation by re-equilibration in skimmed milk at 4°C (overnight) followed by 3 h at 37°C was studied with and without the labeled K-casein tracer. After the micelles were fractionated by ultracentrifugation into sized pellets, the mole ratio of K/p-casein was determined by reverse phase HPLC and the six forms of phosphorylated p-casein were quantitated by anion exchange HPLC. In all systems, the relative amount of K-casein increased inversely with the micelle size, suggesting a surface location for K-casein in the micelles.</p> <p>Support for the surface location also came from the reequilibrated 3H-K-casein micelle study, where the labeled K-casein increased linearly with the micelle surface area/volume ratio. Of the p-caseins, 0-P and 1-P showed greatest variability with micelle size. The proportion of 0-P within the (3-casein fraction decreased with decreasing micelle size but to a greater extent in the re-equilibrated system compared with the native. This indicates that the lack of ability to form Ca++ ion bridges permitted 0-P p-casein to dissociate at low temperatures but hampered reassociation at 37°C. These observations suggest the biosynthetic process is not as simple as component p-Casein with 1-P appeared to increase as the micelle surface area increased. aggregation from whey solution. supporting a surface position for 1-P and its potential to stabilize micelles against precipitation by Ca++. Collectively these findings support a surface position for K-casein in agreement with the Slattery-Evard model for bovine milk micelles. However, the presence of p-caseins with different properties, due to levels of phosphorylation, makes the human micelle more complex.</p>","abstract_has_math":false,"creators":["Dev, Barbara C."],"institution":null,"degree_name":"Doctor of Philosophy (PhD)","degree_level":"Dissertation","degree_discipline":"Biochemistry","degree_department":null,"school":null,"contributors":["Charles W. Slattery","E. Clifford Herrmann","George T. Javor","Subburaman Mohan","R. Bruce Wilcox"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":1990,"date_issued":"1990-08-01T07:00:00Z","date_published":"1990-08-01T07:00:00Z","updated_at":"2026-07-24T02:53:08Z","subjects":["Biochemistry","Milk, Human -- chemistry; Micelles; Caseins -- analysis"],"languages":["English"],"rights":["This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarsrepository.llu.edu/etd/601","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Charles W. Slattery","E. Clifford Herrmann","George T. Javor","Subburaman Mohan","R. Bruce Wilcox"]},{"key":"dc:creator","label":"Author","values":["Dev, Barbara C."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"thesis:degree_discipline","label":"Discipline","values":["Biochemistry"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Biochemistry","Milk, Human -- chemistry; Micelles; Caseins -- analysis"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["English"]},{"key":"dc:rights","label":"Dc Rights","values":["This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarsrepository.llu.edu/etd/601"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Human milk K-casein was isolated from the acid-precipitated casein fraction on Sephadex G-200 and Mono Q HPLC. Samples of K-casein purified from different donors were found similar in both amino acid and carbohydrate composition. A molar extinction coefficient of 11.2 was determined on the basis of amino acid analysis with a norleucine internal standard. Tracer K-casein for human micelle studies was 3H-labeled in the sialic acid moiety of its carbohydrate. The human micelle system was investigated in its native form at 37°C. Micelle reformation by re-equilibration in skimmed milk at 4°C (overnight) followed by 3 h at 37°C was studied with and without the labeled K-casein tracer. After the micelles were fractionated by ultracentrifugation into sized pellets, the mole ratio of K/p-casein was determined by reverse phase HPLC and the six forms of phosphorylated p-casein were quantitated by anion exchange HPLC. In all systems, the relative amount of K-casein increased inversely with the micelle size, suggesting a surface location for K-casein in the micelles.
Support for the surface location also came from the reequilibrated 3H-K-casein micelle study, where the labeled K-casein increased linearly with the micelle surface area/volume ratio. Of the p-caseins, 0-P and 1-P showed greatest variability with micelle size. The proportion of 0-P within the (3-casein fraction decreased with decreasing micelle size but to a greater extent in the re-equilibrated system compared with the native. This indicates that the lack of ability to form Ca++ ion bridges permitted 0-P p-casein to dissociate at low temperatures but hampered reassociation at 37°C. These observations suggest the biosynthetic process is not as simple as component p-Casein with 1-P appeared to increase as the micelle surface area increased. aggregation from whey solution. supporting a surface position for 1-P and its potential to stabilize micelles against precipitation by Ca++. Collectively these findings support a surface position for K-casein in agreement with the Slattery-Evard model for bovine milk micelles. However, the presence of p-caseins with different properties, due to levels of phosphorylation, makes the human micelle more complex.
"]},{"key":"dc:title","label":"Title","values":["K-casein and its Interaction in Human Milk Micelles"]}]}],"canonical_facts":{"dc:contributor":["Charles W. Slattery","E. Clifford Herrmann","George T. Javor","Subburaman Mohan","R. Bruce Wilcox"],"dc:creator":["Dev, Barbara C."],"dc:description.abstract":["Human milk K-casein was isolated from the acid-precipitated casein fraction on Sephadex G-200 and Mono Q HPLC. Samples of K-casein purified from different donors were found similar in both amino acid and carbohydrate composition. A molar extinction coefficient of 11.2 was determined on the basis of amino acid analysis with a norleucine internal standard. Tracer K-casein for human micelle studies was 3H-labeled in the sialic acid moiety of its carbohydrate. The human micelle system was investigated in its native form at 37°C. Micelle reformation by re-equilibration in skimmed milk at 4°C (overnight) followed by 3 h at 37°C was studied with and without the labeled K-casein tracer. After the micelles were fractionated by ultracentrifugation into sized pellets, the mole ratio of K/p-casein was determined by reverse phase HPLC and the six forms of phosphorylated p-casein were quantitated by anion exchange HPLC. In all systems, the relative amount of K-casein increased inversely with the micelle size, suggesting a surface location for K-casein in the micelles.
Support for the surface location also came from the reequilibrated 3H-K-casein micelle study, where the labeled K-casein increased linearly with the micelle surface area/volume ratio. Of the p-caseins, 0-P and 1-P showed greatest variability with micelle size. The proportion of 0-P within the (3-casein fraction decreased with decreasing micelle size but to a greater extent in the re-equilibrated system compared with the native. This indicates that the lack of ability to form Ca++ ion bridges permitted 0-P p-casein to dissociate at low temperatures but hampered reassociation at 37°C. These observations suggest the biosynthetic process is not as simple as component p-Casein with 1-P appeared to increase as the micelle surface area increased. aggregation from whey solution. supporting a surface position for 1-P and its potential to stabilize micelles against precipitation by Ca++. Collectively these findings support a surface position for K-casein in agreement with the Slattery-Evard model for bovine milk micelles. However, the presence of p-caseins with different properties, due to levels of phosphorylation, makes the human micelle more complex.
"],"dc:identifier":["https://scholarsrepository.llu.edu/etd/601"],"dc:language":["English"],"dc:rights":["This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights."],"dc:subject":["Biochemistry","Milk, Human -- chemistry; Micelles; Caseins -- analysis"],"dc:title":["K-casein and its Interaction in Human Milk Micelles"],"thesis:degree_discipline":["Biochemistry"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-24T02:53:08Z"}