In the present study, we report the structure of the free and drug-bound Fab fragment of a high affinity anti-methotrexate antibody and perform a thermodynamic analysis of the binding process. The anti-methotrexate Fab fragment features a remarkably rigid tunnel-like binding site that extends into a water channel serving as a specialized route to move solvent out and into the site upon ligand binding and dissociation. This new finding in antibody structure-function relationships directly relates to the fast association (1 × 10⁷ M⁻¹ s⁻¹) and slow dissociation (4 × 10⁻⁵ s⁻¹) rates determined for mAb ADD056, resulting in a very strong binding with a K(D) ~ 3.
View Article and Find Full Text PDFIn this article, we demonstrate how the application of biophysical tools facilitates the design of robust immunoassays. The binding characteristics of the reagents used in an immunoassay determine the assay response to the analyte concentrations. We applied several biophysical methods to obtain pertinent equilibrium and kinetic coefficients and used this information in the design of a microparticle-based immunoassay for detection of neutrophil gelatinase-associated lipocalin (NGAL), which is a new diagnostic marker of acute kidney injury (AKI).
View Article and Find Full Text PDFObjective: We investigated the mechanism by which the ARCHITECT cyclosporine (CsA) chemiluminescent microparticle immunoassay (CMIA) eliminates cross-reactivity to CsA metabolites AM1 and AM9, despite its use of a monoclonal antibody which shows cross-reactivity in fluorescence polarization immunoassays.
Design And Methods: The CMIA was accomplished by incubating an extracted blood sample with magnetic microparticles coated with a very low amount of anti-CsA antibody. After a wash step the microparticles were incubated with a chemiluminescent CsA tracer, followed by a second wash step and measurement of chemiluminescence.
The recent remarkable rise in biomedical applications of antibodies and their recombinant constructs has shifted the interest in determination of antigenic epitopes in target proteins from the areas of protein science and molecular immunology to the vast fields of modern biotechnology. In this article, we demonstrated that measuring binding induced changes in two-dimensional NMR spectra enables rapid determination of antibody binding footprints on target protein antigens. Such epitopes recognized by six high-affinity monoclonal murine antibodies (mAbs) against human neutrophil gelatinase-associated lipocalin (NGAL) were determined by measuring chemical shifts or broadening of peaks in (1)H-(15)N-TROSY HSQC and (1)H-(13)C HSQC spectra of isotope-labeled NGAL occurring upon its binding to the antibodies.
View Article and Find Full Text PDFB-type natriuretic peptide (BNP) is a naturally secreted regulatory hormone that influences blood pressure and vascular water retention in human physiology. The plasma BNP concentration is a clinically recognized biomarker for various cardiovascular diseases. Quantitative detection of BNP can be achieved in immunoassays using the high-affinity monoclonal IgG1 antibody 106.
View Article and Find Full Text PDFStructure-function studies of antibody-antigen systems include the identification of amino acid residues in the antigen that interact with an antibody and elucidation of their individual contributions to binding affinity. We used fluorescence correlation spectroscopy (FCS) and alanine-scanning mutagenesis to characterize the interactions of brain natriuretic peptide (BNP) with two monoclonal antibodies. Human BNP is a 32 amino acid residue long cyclic polypeptide with the ring structure confined between cysteines in positions 10 and 26.
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