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Biomedical subjects

J Lyngbye

Publications and source records attributed to J Lyngbye.

At least 37 records · Page 2Linked to original sources
PubMed1981

Evidence that the low-affinity folate-binding protein in erythrocyte hemolysate is identical to hemoglobin.

Gel filtration studies on erythrocyte hemolysate demonstrated the presence of a folate binding protein, apparently of the low-affinity type, that co-elutes with hemoglobin. Further, the folate binder eluted with a low salt concentration after DEAE-Sepharose CL-6B anion-exchange chromatography of erythrocyte hemolysate at pH 6.3. The chromatographic behavior of hemoglobin labeled with [3H]folate was so similar to that of the present binder as to suggest that the folate binder in erythrocytes is in fact hemoglobin.

Carrier Proteins↗
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

Pregnancy-specific beta 1-glycoprotein (SP1) determined by means of electroimmunoassay, radial immunodiffusion and nephelometry.

A comparison has been made between rocket-immunoelectrophoresis (RIE), radial immunodiffusion (RID) and automated immunonephelometry (AIP) in the assay of pregnancy-specific beta 1-glycoprotein (SP1) in serum from pregnant women. Using RIE an interaction was demonstrated between the various SP1-reactive molecular populations causing a bias of up to 10%. An interaction corresponding to this phenomenon cannot be demonstrated when using RID and AIP. When correlating the serum-SP1 concentration of samples containing various ratios of SP1-reactive molecules by means of RIE, RID and AIP, it was demonstrated that there was no correlation between the results achieved using one method compared to the results achieved by either of the other methods. The results achieved using one method can therefore exclusively be judged from reference values determined using the same method. The analysis time is essentially shorter with AIP than with RIE and RID.

Female↗
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↗