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At least 469 records · Page 26Linked to original sources
PubMed1978

Quantitative studies on competitive ligand binding to bovine serum albumin by use of the spin label 5-doxyl dodecanoic acid.

The binding of the spin label 5-doxyl dodecanoic acid to bovine serum albumin in phosphate buffer at pH 7.4 was studied by electron spin resonance spectroscopy. Free label and label bound to serum albumin could be quantitatively measured and evaluated from the superposition spectra of these two species with no previous separation. The efficiency relative to the spin label as competitors for binding to serum albumin was studied with salicylic acid and some fatty acids of medium length. The results were represented both by the stoichiometric model involving equilibrium constants Ki, by binding isotherms constructed from the Ki values, and by a purely graphical representation of the experimental data points without connection with any special binding model.

Binding, Competitive↗
PubMed1984

Assessment of the value of a competitive protein binding radioassay of folic acid in the detection of folic acid deficiency.

The diagnostic value of the Becton Dickinson Radioassay Kit (125I) for the the assay of red cell folate has been investigated. The assay was acceptable with regards to precision but was non-linear with changing packed cell volume. Sensitivity of the assay was satisfactory, with 24 of 25 folate deficient patients giving red cell folate values which fell below the reference range. Specificity of the assay in the detection of folate deficiency was less satisfactory. As with microbiological assays, a considerable proportion of vitamin B12 deficient patients had low red cell folate values. In addition, low concentrations were found in 12% of patients who were unlikely to be deficient in either vitamin B12 or folic acid.

Binding, Competitive↗
PubMed1990

Distribution of beta 1- and beta 2-adrenoceptors in mouse trachea and lung: a quantitative autoradiographic study.

1. Binding and quantitative autoradiography were used to detect [125I]-iodocyanopindolol (I-CYP) associated with beta 1- and beta 2-adrenoceptors in mouse tracheal epithelium and airway smooth muscle as well as in lung parenchymal tissue. 2. Specific I-CYP binding to slide-mounted tissue sections of both trachea and parenchyma was of high affinity (KD = 49.0 pM, n = 3, trachea; KD = 118.9 pM, n = 3, parenchyma) and saturable, involving single populations of non-interacting binding sites (Hill coefficient nH = 1.00 +/- 0.02, trachea; nH = 0.99 +/- 0.03, parenchyma). 3. Direct measurement of tissue radioactivity also showed that specific I-CYP binding was competitively inhibited in the presence of the beta-adrenoceptor antagonists (-)-propranolol (non-selective), CGP 20712A (beta 1-selective) and ICI 118,551 (beta 2-selective). Analysis of the competition binding curves for the two selective antagonists revealed mixed populations of beta 1- and beta 2-adrenoceptors in the approximate proportions 33% and 67% respectively in mouse trachea and 28% and 72% respectively in mouse lung parenchyma. 4. Densities of autoradiographic grains derived from specific I-CYP binding to alveolar wall tissue and to tracheal epithelium and airway smooth muscle were quantified by a computer-assisted image analysis system, which allowed the construction of competition binding curves in the presence of the selective beta-adrenoceptor antagonists CGP 20712A and ICI 118,551. Analysis of these data demonstrated that in alveolar wall, beta 1- and beta 2-adrenoceptors co-existed in the proportions 18% and 82%, respectively. 5. Quantitative autoradiographic analyses also showed that beta 1- and beta 2-adrenoceptors were differentially distributed in tracheal epithelium and airway smooth muscle. The beta 2-adrenoceptor subtype accounted for 71% of all beta-adrenoceptors in epithelium. Conversely, beta l-adrenoceptors which mediate relaxant responses of mouse trachea to beta,-adrenoceptor agonists (Henry & Goldie, 1990), accounted for 69% of all beta-adrenoceptors in the airway smooth muscle.

Adrenergic beta-Antagonists↗
PubMed1992

Competition for binding to insulin-like growth factor (IGF) binding protein-2, 3, 4, and 5 by the IGFs and IGF analogs.

The insulin-like growth factors (IGF) I and II bind to IGF binding proteins (BP) with high affinity. The affinity of each of the IGFs for individual BPs and the regions of the IGF-I molecule that are required for this high affinity binding have been defined only for IGFBP-1 and IGFBP-3. The present studies have determined the affinity of several IGF analogs (prepared using in vitro mutagenesis) for pure IGFBP-2, 3, 4, and 5. The results show IGFBP-2 binds these analogs in a manner similar to IGFBP-1. For example, a mutation in the A chain region (positions 49, 50, 51) or B chain (positions 3, 4) results in greater than 20-fold reduction in affinity for either IGFBP-1 or 2. In contrast, mutations in the A chain region have minimal effect on binding to IGFBP-3, whereas substitutions at the 3, 4, 15, 16 positions of the B chain reduce IGF-I affinity by at least 50-fold. At pH 7.4, binding of the analogs to IGFBP-4 is less affected by substitutions at the B chain 3, 4 positions compared to IGFBP-1, 2, and 3, but IGFBP-4 affinity for analogs containing the A chain substitutions is greatly reduced similarly to IGFBP-1 and 2. Binding to IGFBP-5 is greatly reduced by either A or B chain substitutions and most of the mutations result in greater than 100-fold reduction in affinity. Acidic pH 6.0 was associated with increased affinity of IGFBP-4 for the A chain containing mutants. The results indicate that only IGFBP-1 and 2 have nearly identical affinity for each of these analogs, whereas IGFBP-3, 4, and 5 have similarities and significant differences. The findings suggest that different binding proteins have differential structural requirements for optimal IGF-I binding.

Animals↗