Biomedical subjects
Publications and source records attributed to S I Hansen.
The folate-binding protein in cow's whey was purified by affinity chromatography on folate or methotrexate-AH-Sepharose 4B. A change in basic binding properties of the protein occurred probably due to the fact that material removed during affinity chromatography contains a cofactor of great importance to folate binding.
The SMAC method for alkaline phosphatase was modified inorder to determine the enzyme activity according to the Scandinavian recommended method [1]. The method is not strictly 'Scandinavian', but the correlation with the strict Scandinavian method performed on the LKB 8600 Reaction rate analyzer was excellent. The modified method was linear up to at least 2000 U/l.
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Folate in cow's milk was strongly bound to a minor whey protein. Methotrexate inhibited the folate binding in a log dosis dependent manner, but was a rather weak inhibitor. The binding mechanism of folate changed from a cooperative to a non-cooperative type in the presence of methotrexate. This model system could be used in investigations on human body fluids and tissues.
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Human whey was subjected to gel chromatography. Two folate binding protein fractions wer eluted: a major one (Mr congruent to 30,000) and a minor one (Mr greater than 200,000). The former folate binding fraction (FB) could be isolated from whey by means of ion exchange chromatography. Equilibrium dialysis experiments with whey and isolated FB indicated the existence of cooperatively interacting sites in folate binding. The folate analogue methotrexate inhibited folate binding. Inhibition was apparently of a competitive type since methotrexate did not reduce maximum binding capacity. Cooperativity was lost in the presence of methotrexate. Binding affinity was inversely proportional to the concentration of FB suggesting involvement of a polymerizing protein system in binding. None of the other fractions eluted on the ion exchange column could bind folate.