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Results for “ligand-binding assay”

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11 recordsLinked to original sources
PubMed1977

Serum thyroxine-binding globulin: determination by competitive ligand-binding assay in thyroid disease and pregnancy.

Serum thyroxine-binding globulin (TBG) concentrations were measured by competitive ligand-binding assay in normal subjects and patients with a variety of abnormalities of thyroid hormone production or TBG production. The mean serum TBG concentration in 73 normal adults was 3.4 +/- 0.6 mg/100 ml. No correlations with age, sex or serum thyroxine (T4) or triiodothyronine (T3) concentrations were found. Serum TBG concentrations were normal in patients with hyperthyroidism. They were significantly elevated in hypothyroid patients, and fell to normal with thyroxine treatment. In pregnant women, serum TBG concentrations were markedly increased, being 7.1 +/- 1.2 (mean +/- SD) mg/100 ml in women in their first trimester, 9.0 +/- 1.0 mg/100 ml in the second trimester and 8.9 +/- 1.6 mg/100 ml in the third trimester. There was a positive correlation between serum TBG concentration and both serum T4 and serum T3 concentrations in pregnant women. Competitive ligand-binding assay is a simple and reliable method for TBG asay and yields results similar to those of electrophoretic saturation techniques.

Acromegaly↗
PubMed1979

Serum levels of methotrexate by the ligand-binding assay after "high-dose" therapy for osteosarcoma.

The method of Arons et al. (Cancer Res. 35:2033-2038, 1975) for assaying methotrexate (MTX) was used to monitor serum levels of the drug attained in 18 patients with osteosarcomas. The patients received either 100 mg or 200 mg of MTX/kg via a 6-hour infusion. With one fatal exception, unacceptable toxicity to MTX was prevented by leucovorin. Serum levels of the drug were assayed routinely at 6, 12, and 18 hours after termination of the infusion. Although significantly higher serum levels of MTX were observed at 6 hours after the infusion of 200 mg MTX/kg than after 100 mg/kg, the variation in rate of clearance of individual patients masked any subsequent dosage-related differences. The mean half-time for clearance of MTX was similar irrespective of the dosage of MTX and was 2.91 +/- 1.51 hr for 53 treatments. The single incidence of toxicity, requiring hospitalization, was accompanied with markedly higher serum levels of MTX at 18 hours, but not at either 6 or 12 hours after termination of the drug infusion, and by a slightly slower rate of clearance, 6.2 hours. Certain minor adaptations were incorporated in the original assay to simplify the analysis of data.

Drug Therapy, Combination↗
PubMed1977

A simple ligand-binding assay for thyroxine-binding globulin on reusable Sephadex columns.

A method for the assay of thyroxine-binding globulin on reusable Sephadex G-25 (fine) columns is described. It depends upon elution by diluted iodothyronine-free serum of protein-bound [125 I]thyroxine from the columns under conditions where binding to thyroxine-binding prealbumin and albumin are abolished. It is simple, rapid and precise and permits determinations in large numbers of samples. Values (mg/l; mean +/- S.D.) were: normals 31.6 +/- 5.4, hyperthyroid 28.3 +/- 4.8, hypothyroid 40.6 +/- 7.5, oral contraceptives 40.1 +/- 6.8, pregnant 50.3 +/- 5.4, cirrhotics 20.7 +/- 4.3. Concentrations were reduced in serum heated at 56 degrees C, while the uptake of [125 I]triiodothyronine was increased. There was a significant negative correlation between thyroxine-binding globulin concentration and triiodothyronine uptake in the heated serum samples and in euthyroid subjects.

Anion Exchange Resins↗
PubMed2026

The Gyrolab platform for immunogenicity assessment and biotherapeutic and biomarker analysis: technical advances and bioanalytical applications.

Gyrolab is an automated ligand‑binding assay platform designed for the quantification of proteins with high sensitivity and broad dynamic range. Its low minimum required dilution and microfluidic disc format enable efficient sample processing while maintaining assay robustness, making it a valuable tool across drug‑development stages. This review summarizes published applications of Gyrolab for pharmacokinetic and toxicokinetic analysis and immunogenicity assessment through anti‑drug antibody detection. In addition, the platform's high-volume assay discs have facilitated its use in biomarker studies, allowing quantification of low‑abundance analytes. Representative examples from the literature are presented together with key assay elements, including analytes, matrices, dynamic ranges, and critical reagents. Because assay replicates remain an important consideration for Gyrolab workflows, recent publications addressing singlet versus duplicate strategies and their impact on data interpretation are also discussed. Finally, we provide real analytical data visualized using a three‑dimensional Gyrolab viewer to illustrate variability in duplicate measurements and to highlight future opportunities for improving assay reliability.

Humans↗
PubMed2026

High-Throughput Screening Identifies Small-Molecule Inhibitors of the Tau-LRP1 Interaction.

The cellular uptake and propagation of tau are central features of tauopathies, including Alzheimer's disease, and are mediated by the endocytic receptor low-density lipoprotein receptor-related protein 1 (LRP1). While prior studies have implicated LRP1 in tau binding and internalization, the biochemical features of this interaction and its suitability for therapeutic targeting remain incompletely defined. Here, we establish a quantitative and scalable framework to interrogate the tau-LRP1 interaction and identify small-molecule modulators. We engineered and purified the LRP1 ligand-binding domain 4 (BD4), a key region mediating tau interaction, and developed multiple orthogonal assays, including fluorescence polarization, split luciferase complementation, and time-resolved FRET, to measure LRP1-BD4 interactions with tau and a known peptide ligand. Across assay formats, we observe consistent binding affinities in the nanomolar range and demonstrate competitive displacement by tau, receptor-associated protein (RAP), and a peptide ligand, supporting overlapping binding interfaces. Leveraging these platforms, we performed small molecule high-throughput screening and identified a set of candidate inhibitors of the LRP1-BD4-tau interaction. Selected compounds reduced tau uptake in a cellular assay, phenocopying competitive inhibition by tau and a peptide ligand. Together, these studies define the LRP1-BD4-tau interaction as a biochemically tractable and druggable interface and establish an integrated discovery pipeline linking mechanistic characterization to functional cellular outcomes. This work provides a foundation for the development of therapeutic strategies targeting LRP1-mediated tau uptake.

Journal Article↗
PubMed2026

Divergent PXR function in seals: Endocrine adaptation or functional loss?

Seals accumulate xenobiotics through dietary biomagnification and exposure to polluted marine environments, with contaminants concentrating in their blubber. Biotransformation mitigates xenobiotic toxicity by converting lipophilic compounds into excretable hydrophilic metabolites, a process coordinated by nuclear receptors including the Pregnane X Receptor (PXR), whose plastic ligand-binding domain enables broad xenobiotic sensing. By examining PXR in pinnipeds, we investigated the evolutionary conservation and functional characterization of PXR using genomic sequence analysis, protein structural prediction, and transactivation assays, revealing broadly conserved structural features alongside species-specific functional divergence in receptor responsiveness to environmental stressors. Specifically, the obtained results highlight divergent gene and functional landscapes with ORF-disrupting mutations identified in Monachus monachus and Neomonachus schauinslandi that abolish receptor activation toward known PXR ligands. In contrast, Leptonychotes weddelli retained an intact PXR ORF but showed reduced receptor activity, revealing functional divergence in PXR among pinnipeds.

Biotransformation↗
PubMed1975

Studies on Z-Fraction. I. Isolation and partial characterization of low molecular weight ligand-binding protein from rat hepatic cytosol.

The Z-fraction has been defined operationally as a ligand-binding (bilirubin sulfobromophthalein) portion of rat hepatic cytosol that elutes in the molecular weight region of 10(4) daltons after gel filtration. Polyacrylamide gel electrophoreses under different conditions, as well as binding stoichiometry, confirm the anticipated heterogeneity of the Z-fraction. Three factors have contributed to the subsequent resolution of the Z-fraction and partial characterization of that protein within the fraction with ligand-binding properties (Z-protein): (1) the use of hexachlorophene as ligand; (2) the inclusion of glycerol, 20%, during isolation to prevent aggregation and loss of binding-activity; and (3) the development of a charcoal binding assay. Upon ion exchange chromatography, the Z-fraction resolves into a group of distinct protein components and an unidentified material with a high 260/280 nm absorbancy ratio. The one protein component with binding capacity exhibits homogeneity on polyacrylamide gel electrophoresis (11% gel, Ann. N.Y. Acad. Sci. 121, 404-427, 1964; and 15% gel with SDS). With use of the charcoal method, apparent dissociation constants for the interaction between Z-protein and hexachlorophene, bilirubin and L-thyroxine, were found to be 20, 50, and 350 muM, respectively. The Scatchard plot generated upon extrapolation an n value of 1.0 with assumption of a molecular weight for Z-protein of 10(4) daltons.

Animals↗
PubMed1979

Radiochemical method for measuring plasma clearance and urinary excretion of pteroylglutamic acid.

A radiochemical procedure is described for specific determination of pteroylglutamate in serum and urine. This method depends on denaturation of methyltetrahydrofolate with peroxide and measurement of the residual folate by a ligand-binding radioassay. The binding determinant for the radioassay is a folate-binding protein, partially purified from chronic myelogenous lekemia cells, that has low affinity for the reduced folates and thus will preferentially measure residual pteroylglutamate rather than any nondenatured residual methyltetrahydrofolate. We used this assay to measure the clearance from plasma and the urinary excretion of pteroylglutamate and a small fraction of serum folate that is stable to this oxidation procedure. The plasma clearance after intravenous injection is characterized by an initial rapid distribution phase followed by a second, slower metabolic phase; after about 2 h all of the administered pteroylglutamate has been cleared from the blood. The peak concentration of total folate in serum 1--2 min after administration of pteroylglutamate exceeded the sum of the endogenous stable and baseline serum folate, indicating that a reduced labile folate was released from the liver and perhaps from other tissues. This reduced folate had a slower metabolic clearance rate and was excreted to some extent in urine. Only 2.3 and 7.9% of the pteroylglutamate administered to two normal subjects was excreted as stable folate.

Folic Acid↗
PubMed1975

A direct ligand-binding radioassay for the measurement of methotrexate in tissues and biological fluids.

A direct ligand-banding radioassay for methotrexate (MTX) has been developed using dihydrofolate reductase, contained in the lysate of L1210 leukemia cells, as the binding determinant. The procedure is a two-phase reaction system where standard MTX concentrations or the sample being assayed in incubated with the reagent lysate in the first phase, and [3H]MTX is then added in the second phase to titrate the remaining unoccupied binding sites on the enzyme. This method eliminates the need for measuring the residual catalytic activity of the enzyme. The sensitivity of the radioassay is limited only by the specific activity of the [3H]MTX and how approximates 10 pg of the drug. Folic acid, methyltetrahydrofolate, formyltetrahydrofolate, and dehydrofolate in concentrations that are physiological do not interfere in the radioassay. Both mercaptoethanol and reduced nicotinamide andnine dinucleotide phosphate increase the binding capacity of the lysate for MTX; but the reduced nucleotide also increases the affinity of the enzyme for the inhibitor. MTX added to serum can be assayed without extraction if the concentration is greater than 500 pg/ml and recovery of the drug added to serum is about 92%. MTX has been assayed in serum, spinal fluid, and urine of patients who were treated with this drug. It has also been assayed in the lysates of L1210 cells from C57BL X DBA/2 F1 mice treated with MTX. The procedure is simple, rapid, and accurate and should permit better correlation of the therapeutic and toxic effects of MTX with blood concentrations over long-term treatment periods.

Animals↗
PubMed1977

Ligand-binding radioassay for the antifolate compounds: application in patients receiving methotrexate.

The general principles of ligand-binding radioassays are reviewed and a specific noncompetitive system is described for the measurement of methotrexate (MTX) using dihydrofolate reductase as the binding determinant. This type of radioassay can also be exploited to measure any antifolate compound which binds to this enzyme even if [3H]MTX is used as the tracer. The radioassay has now been used to measure MTX in all types of body fluids, tissue extracts, and rbc lysates from patients receiving this drug.

Dose-Response Relationship, Drug↗