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Biomedical subjects

S I Hansen

Publications and source records attributed to S I Hansen.

68 records · Page 4Linked to original sources
PubMed1980

High and low affinity binding of folate to proteins in serum of pregnancy women.

Binding of [3H]folate to proteins in serum of pregnant women was studied in equilibrium dialysis experiments (pH 7.4, 37 degrees C). A Scatchard analysis revealed the presence of high-affinity (Kass = 10(10) M(-1), N = 0.4 nM folate) and low-affinity sites. The high-affinity folate binding protein (Mr approximately 30 000--35 000) appeared in front effluent after application of serum to a DEAE-Sepharose CL-6B column equilibrated with 0.05 M imidazole buffer (pH 6.3)/30 mM NaCl. Low-affinity binding protein eluted from the column after a rise in NaCl concentration to 1 M was mainly similar to albumin. A minor part was, however, associated with a large molecular size (Mr > 200 000) protein, probably alpha 2-macroglobulin. High-affinity binding which displayed positive cooperativity was saturated at folate concentrations above 10(-10) M. Folate dissociation was a complex process consisting of an initial rapid phase (terminated within 48 h) followed by a slow release. At pH 3.5 dissociation became rapid and complete. Purified methotrexate had no effect on high-affinity binding, whereas N10-methylfolate (an impurity in the methotrexate preparation) acted as a potent inhibitor. Low-affinity binding was proportional to the folate concentration within the range 10(-10)--10(-7) M. Dissociation of folate was rapid.

Binding Sites↗
PubMed1980

High-affinity binding of folate to a protein in serum of male subjects.

The binding pattern of [3H]folate in the serum of male subjects was studied in equilibrium dialysis experiments (pH 7.4, 37 degrees C). It was possible to distinguish between a high (association constant, Kass = 10(10) (mol/l)-1; maximum binding of folate = 0.6 nmol/l) and a low affinity type of binding. The high-affinity binder was a trace protein (molecular size approximately 35 000) which was eluted with 30 mmol/l NaC, (pH 6.3) from serum subjected to DEAE-Sepharose CL-6B chromatography. The low-affinity binding activity mainly associated with albumin was eluted with 1 mmol/l NaCl. High-affinity binding was depressed at 7 degrees C (Kass = 10(9) (mol/l)-1). Furthermore, methotrexate acted as a weak inhibitor of high-affinity binding, the molar methotrexate/folate ratio being 100/1 at 50% inhibition.

Chromatography, Ion Exchange↗
PubMed1980

A high affinity folate binding protein in umbilical cord serum.

Binding of [3H] folate to proteins in umbilical cord serum was studied in equilibrium dialysis experiments (37 degrees C, pH 7.4). A Scatchard analysis revealed the presence of high affinity (Kass = 9.10(10)1/mol, N = 0.5 nmol per 1 folate) and low affinity binding sites. High affinity binding was almost completely inhibited in the presence of methotrexate. A high affinity folate binding protein (saturated at a folate concentration of 10(-11)mol/l) appeared in the front effluent after application of serum to a DEAE-Sepharose Cl-6B column equilibrated with 0.05 mol/l imidazole buffer (pH, 6.3, 30 mmol/l NaCl), whereas low affinity binding activity mainly associated with albumin eluted from the column following a rise in the NaCl concentration to 1 mol/l. Low affinity binding predominated at folate concentrations above (10(-9) mol/l. The apparent molecular size of the high affinity binder was 35,000 as determined by gel filtration. The physiological role of the high affinity binder is obscure. However, it may represent an intracellular protein regulating folate stores, and its appearance in serum may be incidental to tissue turnover.

Carrier Proteins↗
PubMed1980

Cofactor in serum for high-affinity folate binding in milk.

Affinity-chromatographic purification of the folate-binding protein from whey of cow's milk results in the removal of a heat-resistant cofactor that is important in high-affinity folate binding (Biochim, Biophys. Acta 579: 479, 1979). Thus a shift from negative to positive cooperativity occurred in the presence of cofactor (Biochim, Biophys. Acta 579: 479, 1979). We demonstrate the presence of a similar cofactor in sera from men, pregnant women, and umbilical cords. Even highly diluted (10 000-fold) serum samples were active, and the cofactor was also present in erythrocyte hemolysates (10 000-fold diluted). The identity of the cofactor, which may act as an overall modulator of high-affinity folate binding, is still obscure.

Animals↗
PubMed1980

Chromatographic isolation and characterization of folate binding proteins in porcine intestinal epithelial brush border membrane.

Gel filtration studies on solubilized porcine intestinal epithelial brush border membranes labelled with [3H] folate revealed three distinct protein peaks, Mr approximately 25 000, Mr approximately 80 000 and Mr greater than 130 000 (listed in order of decreasing folate binding affinity). The two large molecular size proteins may represent polymerized forms of the Mr approximately 25 000 peak. Folate binding proteins were eluted in front effluent after DEAE-Sepharose CL-6 B chromatography (pH 6.3, 30 mM NaCl) of a solubilized membrane preparation. This means that the cationic forms of these proteins predominate at pH 6.3. In conclusion, folate binding in brush border membranes display characteristics in many respects similar to those of high-affinity folate binding in other tissues and body fluids.

Animals↗
PubMed1979

Determination of alkaline phosphatase (EC 3.1.3.1) on the SMAC using diethanolamine in a modified manifold.

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.

Alkaline Phosphatase↗
PubMed1978

Effect of methotrexate on folate binding to a folate binding protein in cow's milk.

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.

Animals↗
PubMed1977

Folate binding by human milk protein.

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.

Binding Sites↗
PubMedDate not supplied

Characterization of a folate receptor in parotid gland and a folate binding protein in saliva from humans. Epitope relatedness to human milk folate binding protein.

The present study was performed to establish the antigenic identity and origin of the folate binding protein in human saliva. We identified a folate receptor in human parotid and submandibular gland which immunoreacted with antibodies against human milk folate binding protein, as evidenced by ELISA and immunostaining of ductal epithelium and secretory glandular material. The receptor concentration was 0.4-1.4 nmol 3H-folate bound/g protein. Ligand binding was of a high-affinity (K=10(10) M(-1)) type, exhibited positive cooperativity, a slow radioligand dissociation at pH 7.4, and inhibition by folate analogues. The concentration of immunoreactive folate binding protein in saliva as determined by ELISA with antibodies against human milk folate binding protein was several fold higher than that determined by radioligand binding (nil - 1 nM). This indicates that a major fraction of the immunoreactive material does not bind 3H-folate, and could represent a precursor form of the protein. In conclusion, the folate binding protein in human saliva seems to be a secretory product of the salivary glands. The protein is also epitope-related to folate binding proteins in other human mucosal secretions.

Animals↗