PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 3527481

Solid-phase immunoassay of digoxin by measuring time-resolved fluorescence.

P Helsingius·I Hemmilä·T Lövgren
View original source ↗Export metadata ↓

Abstract

We describe a time-resolved fluoroimmunoassay for the cardiac glycoside digoxin. The assay depends on the competitive distribution of Eu3+-labeled anti-digoxin antibodies between solid-phase-bound digoxin and the digoxin in the sample or standard. After this immunoreaction, the bound fraction of the Eu3+-label is dissociated from the solid phase, converted into a highly fluorescent beta-diketone chelate, and measured in a fluorometer with time-resolution (1230 Arcus, LKB-Wallac). Sample volume is 20 microL, the incubation lasts 30 min, and the concentration range of the assay for digoxin is from 0.25 to 4.0 ng/mL (0.32-5.1 nmol of digoxin per liter). Correlation with an in-house RIA was good (r = 0.97, n = 43). The sensitivity was equivalent to that of most RIAs: 0.2 ng/mL (0.25 nmol/L).

Explore related subjects

AntibodiesCross ReactionsDigoxinEuropiumFluorescent Antibody TechniqueHumansIsotope LabelingReagent Kits, DiagnosticTime FactorsJournal Article

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

P Helsingius, I Hemmilä, T Lövgren. 1986. Solid-phase immunoassay of digoxin by measuring time-resolved fluorescence.. https://pubmed.ncbi.nlm.nih.gov/3527481/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2021

ERBB3 overexpression due to miR-205 inactivation confers sensitivity to FGF, metabolic activation, and liability to ERBB3 targeting in glioblastoma.

In glioblastoma (GBM), the most frequent and lethal brain tumor, therapies suppressing recurrently altered signaling pathways failed to extend survival. However, in patient subsets, specific genetic lesions can confer sensitivity to targeted agents. By exploiting an integrated model based on patient-derived stem-like cells, faithfully recapitulating the original GBMs in vitro and in vivo, here, we identify a human GBM subset (∼9% of all GBMs) characterized by ERBB3 overexpression and nuclear accumulation. ERBB3 overexpression is driven by inheritable promoter methylation or post-transcriptional silencing of the oncosuppressor miR-205 and sustains the malignant phenotype. Overexpressed ERBB3 behaves as a specific signaling platform for fibroblast growth factor receptor (FGFR), driving PI3K/AKT/mTOR pathway hyperactivation, and overall metabolic upregulation. As a result, ERBB3 inhibition by specific antibodies is lethal for GBM stem-like cells and xenotransplants. These findings highlight a subset of patients eligible for ERBB3-targeted therapy.

Antibodies↗
PubMed2007

Concerted activation of the Mdm2 promoter by p72 RNA helicase and the coactivators p300 and P/CAF.

A scarcely studied and under-recognized feature of RNA helicases is their ability to regulate gene transcription. In particular, very little is known about the role of p72 RNA helicase in gene regulation. Here, we have analyzed how this helicase may enhance promoter activity. We demonstrate that p72 RNA helicase forms complexes with the homologous coactivators p300 and CBP in vitro and in vivo, especially leading to an enhancement of the transactivation potential of their C-termini. In addition, we show that the p300/CBP-associated protein (P/CAF) also interacts with p72 RNA helicase, and both this interaction and the binding to p300/CBP are mediated by the N-terminal 63 amino acids of p72 RNA helicase. p300, P/CAF and p72 RNA helicase synergize to stimulate selected promoters, including the Mdm2 one. Notably, downregulation of p72 RNA helicase leads to reduced Mdm2 transcription. Furthermore, our data suggest that p72 RNA helicase activates the Mdm2 promoter in a p53 dependent and independent manner. Collectively, our results have unraveled a mechanism of how p72 RNA helicase can regulate gene transcription, namely by cooperating with p300/CBP and P/CAF. Thereby, p72 RNA helicase may not only be involved in the p53-Mdm2 regulatory loop, but also profoundly impact on the transcriptome through various CBP/p300 and P/CAF interacting proteins.

Antibodies↗
PubMed2007

A smart membrane based on an antigen-responsive hydrogel.

Hydrogel membranes have been fabricated that incorporate antibody/antigen moieties. The permeability of large solutes through these membranes is dependent on the presence of soluble antigen that can compete with the internal interactions between antibody and antigen leading to an increase in gel mesh size. Specifically, the membrane's structure is based on a dextran backbone grafted with a fluorescein isothiocyanate (FITC) antigen and a sheep anti-FITC IgG antibody. The backbone is covalently cross-linked by conjugated divinyl sulfone (DVS) groups. The gel structure is additionally stabilized by affinity crosslinks formed by biospecific interactions between the bound IgG and FITC. FTIR spectra of the gel are consistent with formation of covalent bonds between cysteine groups in the IgG and DVS groups in the dextran. Results obtained using isothermal titration calorimetry (ITC) confirmed the competitive interaction binding between IgG-FITC-dextran and free sodium fluorescein at pH 5.0. Scanning electron microscopy (SEM) of samples prepared using cryofixation and cryofracturing techniques showed that observed changes in permeability correlate with free fluorescein-dependent structural changes in the gel. Three-dimensional images obtained from confocal laser scanning microscopy show that these changes occur throughout the gel and indicate that SEM results are not artifacts of sample preparation. The permeability of these gels, as shown by blue-dextran (12 kDa) diffusion, increases in response to the presence of free fluorescein of the external medium, which causes competitive displacement of the affinity cross-links. Sequential addition and removal of sodium fluorescein showed that these permeability changes are reversible.

Antibodies↗