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Biomedical subjects

J Lyngbye

Publications and source records attributed to J Lyngbye.

At least 19 recordsLinked to original sources
PubMed1985

A high-affinity folate binding protein in normal human leukocytes: ligand binding characteristics, ionic charge and molecular size.

High-affinity binding of [3H]folate to supernatant from homogenized human leukocytes containing large amounts of binding protein displayed apparent positive cooperativity. The DEAE-Sepharose CL-6B chromatographic profile of the supernatant at pH 6.3 contained a major peak of folate binding (Mr approx. 25 000) in the front effluent and a smaller more acidic peak (Mr approx. 25 000) that emerged after a rise in NaCl from 30 mmol/l to 1 mol/l. Triton X-100 solubilized cell sediment from the leukocyte homogenate contained some high-affinity folate binding activity (Mr approx 25 000), typically 5-10% of the total binding activity.

Carrier Proteins↗
PubMed1985

A high-affinity folate binding protein in human cerebrospinal fluid.

Binding of 3H-folic acid to a protein in human cerebrospinal fluid (CSF) was studied in equilibrium dialysis experiments at 37 degrees C and pH 7.4. The binding was of a high-affinity type (10(10) l/mol), and the relative molecular mass of the protein was 25,000 as determined by gel filtration. The concentration of folate binding protein in CSF, expressed as maximum folate bound per 1, was 0.3 nmol/l. This value was of the same order of magnitude as that of serum.

Carrier Proteins↗
PubMed1985

Li+-induced release of the folate binding protein from human granulocytes.

Release of folate binding protein from human leucocytes suspended in isotonic NaCl was studied in experiments where folate binding activity of the suspending medium was determined by equilibrium dialysis (pH 7.4, 37 degrees C) against 3H-folate. Release from leucocytes containing particularly high concentrations of folate binding protein was significantly increased in the presence of 70 mmol/l Li+. The stimulated release was apparently not an osmotic phenomenon since no effect was observed with isomolar Na+/K+. The released protein resembled the folate binding protein in leucocyte lysate as to characteristics of radioligand binding, ionic properties and molecular size. Hence no transformation of the protein seemed to occur during Li+-induced release.

Carrier Proteins↗
PubMed1985

Charge heterogeneity of the folate binding protein in normal human leukocytes.

The DEAE-Sepharose CL-6B chromatographic profile of supernatant from homogenized normal human leukocytes containing large amounts of folate binder revealed two peaks of binding activity. A minor binder (I) eluted with the equilibrating buffer (1 mM sodium phosphate of pH 6.0), while the major binder (II) first eluted after the initiation of a linear phosphate gradient with 200 mM sodium phosphate of pH 7.6 as the limiting buffer. Binder II was thus a more acidic protein since it required elution by a salt-pH gradient. Binding of [3H] folate to binder II was of a high-affinity type (K = 10(10) M-1) and displayed positive cooperativity.

Carrier Proteins↗
PubMed1984

Quantitative and qualitative effects of N10-methylfolate on high-affinity folate binding in human leukocytes.

N10-methylfolate acted as a potent competitive inhibitor of high-affinity [3H] folate binding in human leukocytes, while methotrexate had no effect. Furthermore, folate binding changed into a non-cooperative type in the presence of N10-methylfolate. Hence, in qualitative and quantitative respects, the substrate specificity characteristics of leukocyte folate binding resemble those of other high-affinity folate binding systems.

Binding, Competitive↗
PubMed1983

Dependence of aggregation and ligand affinity on the concentration of the folate-binding protein from cow's milk.

Ultracentrifugation and gel-filtration studies showed that the folate-binding protein from cow's milk possessed a remarkable aggregation tendency at pH 7.4. Aggregation was enhanced in the presence of folate which suggested an interrelationship between the mechanisms of ligand binding and polymerization. The degree of polymerization increased with increasing concentrations of binding protein. Thus, while the monomer prevailed at 1 nM, a polymer composed of more thn 32 monomers was formed at 130 microM. Two characteristics of folate binding, i.e., Scatchard plots that were convex upward and a ligand affinity that was inversely proportional to the concentration of binding protein, could be interpreted in terms of ligand binding to a polymerizing system in which the polymerization equilibria affect the ligand affinity.

Animals↗
PubMed1983

High-affinity folate binding in leukocyte lysate from normal subjects: effect of concentration of binding protein, temperature and pH.

Folate binding in lysate prepared from leukocytes containing large amounts of the folate-binding protein was studied in equilibrium dialysis experiments (pH 7.4, 37 degrees C). Binding displayed positive cooperativity, and the binding affinity increased with decreasing concentration of binding protein (affinity constants in the range of 5 X 10(9) l/mol to 7 X 10(10) l/mol). Both phenomena could be interpreted in terms of ligand binding to a polymerizing system where the affinity of ligand for the oligomer is greater than its affinity for the polymer prevailing at high concentrations of the binding protein. Binding affinity was decreased at a low temperature (7 degrees C) and particularly at pH 5.0 where positive cooperativity also disappeared. The binder (Mr approximately 25,000-30,000) eluted in the front effluent after DEAE-Sepharose CL-6B chromatography of the lysate at pH 6.3.

Animals↗
PubMed1983

Inheritance of high leukocyte folate binding activity. Relationship between folate binding in leukocytes and serum.

Folate binding was determined in leukocyte lysates from relatives of three persons whose leukocytes contained large amounts of folate binding protein. A pedigree analysis showed that high leukocyte folate binding activities occurred with great frequency in these families suggesting a dominant mode of inheritance. Folate binding in serum varied within narrow limits (0.2-0.5 nmol folate/l serum) in persons with leukocyte folate binding activities less than 0.8-1.0 nmol folate per 10(9) cells. A shift to a higher level of serum folate binding (greater than or equal to 1.0 nmol/l serum) was, however, observed at leukocyte folate binding activities above that value.

Carrier Proteins↗
PubMed1983

Characteristics of high-affinity folate binding in human leukocytes.

High-affinity binding of [3H]folate in leukocytes from normal subjects was studied in equilibrium dialysis experiments (pH 7.4, 37 degrees C). Binding displayed positive cooperativity, and the binding affinity increased with decreasing concentration of the binding protein. Both phenomena could be interpreted in terms of ligand binding to a polymerizing system where the affinity of ligand for the oligomer is greater than its affinity for the polymer prevailing at higher concentrations of the binding protein.

Carrier Proteins↗
PubMed1982

Detergent activation of the binding protein in the folate radioassay.

A minor cow's whey protein associated with beta-lactoglobulin is used as binding protein in the competitive radioassay for serum and erythrocyte folate. Seeking to optimize the assay, we tested the performance of binder solutions of increasing purity. The folate binding protein was isolated from cow's whey by means of CM-Sepharose CL-6B cation-exchange chromatography, and further purified on a methotrexate-AH-Sepharose 4B affinity matrix. In contrast to beta-lactoglobulin, the purified protein did not bind folate unless the detergents cetyltrimethylammonium (10 mmol/L) or Triton X-100 (1 g/L) were present. Such detergent activation was not needed in the presence of serum. There seems to be a striking analogy between these phenomena and the well-known reactivation of certain purified membrane-derived enzymes by surfactants (lipids/detergents).

Detergents↗
PubMed1982

Maximum folate binding in leukocyte lysates and sera from blood donors.

Maximum binding of [3H] folate was determined in leukocyte lysates and sera from blood donors with normal hematological parameters. The folate binding activity in leukocyte lysates showed a remarkably great interindividual variation, whereas the folate binding in sera from the same persons showed a rather modest interindividual variation. The folate binding activity in leukocyte lysates is mainly derived from granulocytes since lymphocytes and monocytes from individuals with high content of folate binder in their leukocytes contained less than 1% of the total binding activity.

Adult↗
PubMed1982

Gel filtration profile of folate binding proteins in Triton X-100 solubilized human raw milk.

Solubilization of human raw milk with Triton X-100 gave rise to a two-fold increase in maximum [3H] folate binding as determined in equilibrium dialysis experiments (pH 7.4, 37 degrees C). Gel filtration studies on Triton X-100 solubilized human milk revealed three distinct peaks of protein-bound [3H] folate, Mr approximately 25 000 (38%), Mr greater than or equal to 130 000 (15%) and Mr approximately 100 000 (47%). The first peak was identical to the folate binder previously isolated from human whey, while the second peak most likely represented a particulate membrane-bound form of that binder. The third so far undescribed peak (Mr greater than or equal to 100 000) seemed to contain hydrophobic residues, and might be encapsulated in Triton X-100 micelles. This peak may represent a Triton X-100 solubilized split product of the large particulate binder.

Carrier Proteins↗
PubMed1981

High-affinity folate finding in chronic myelogenous leukaemia serum, relationship of binding characteristics to activity of disease and binder concentration.

High-affinity binding of [3H]folate to chronic myelogenous leukaemia serum displayed positive co-operativity. There seemed to be a relationship between the concentration level of binder in serum and the activity of the disease in the sense that the serum level of binder during remission fell to a value similar to that of normal serum. This was accompanied by a shift from positive co-operativity to the binding type of normal serum, i.e. negative co-operativity. The data support the hypothesis that the different characteristics of high-affinity folate binding in chronic myelogenous leukaemia and normal serum are related to parallel differences in the serum level of binder.

Carrier Proteins↗
PubMed1981

High-affinity binding of folate to a serum protein in chronic myelogenous leukemia: effect of binder concentration, pH, and temperature.

Serum from a patient with chronic myelogenous leukemia was subjected to anion-exchange chromatography on DEAE-Sepharose CL-6B. High-affinity binding of [3H]folate to front effluent, eluted at a low salt gradient, was studied in equilibrium-dialysis experiments (37 degrees C, pH 7.4). As suggested by the data, folate binding displayed positive cooperativity. Dilution of the binder solution resulted in a shift to a simple non-cooperative binding type and increased binding affinity. Furthermore, binding was inhibited at pH 5.0 and at low temperature (7 degrees C). This study demonstrates important similarities between high-affinity folate binding in milk and serum: positive cooperativity and dependence of binding affinity on concentration of binder. Identical mechanisms may underly these phenomena in milk and serum. The apparent relationship between binding type and concentration of binder shown herein seems to agree fairly well with recent observations on sera from groups of healthy persons.

Carrier Proteins↗
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↗