Activity ligand-binding

Enzymatic activity, ligand binding or transport capacity Cleavage C3 Leu Control... 

PTKs are monomeric in the active form, and consist of an extracellular binding domain, single membrane-associated a-helix and cytosolic domain with the kinase activity. Ligand binding induces dimerization and autophosphorylation that enables binding to adaptor molecules. These molecules connect the receptor to the signal transmitting biopolymers. 

If the iodinated protein will be used in bioassays, check for biologic activity (antigenicity, enzymic activity, ligand binding, etc.) in comparison with the not-labeled starting material. 

A series of cyclic conformationally constrained peptides related to somatostatin were designed, synthesized and tested for opioid receptor interaction by Hruby and his collaborators. Compounds (17)-(22) were found to be pure opioid antagonists (GPI) with high affinity (IC50 = 1.2 to 4.3 nM) and exceptional selectivity for p over S opioid receptors (Table 3.1) and with minimal or no somatostatin-like activity (ligand binding assays)[63-65]. 

Pretzlaff, R. K., Xue, V. W., Rowin, M. E. (2000). Sialidase treatment exposes the pi—integrin active ligand binding site on HL60 cells and increases binding to fibronectin. Cell Adhes. Commun., 7,491-500. 

The essential feature of the AAA is a comparison of active and inactive molecules. A commonly accepted hypothesis to explain the lack of activity of inactive molecules that possess the pharmacophoric conformation is that their molecular volume, when presenting the pharmacophore, exceeds the receptor excluded volume. This additional volume apparently is filled by the receptor and is unavailable for ligand binding this volume is termed the receptor essential volume [3]. Following this approach, the density maps for each of the inactive compounds (in their pharm conformations superimposed with that of active compounds) were constructed the difference between the combined inactive compound density maps and the receptor excluded volume represents the receptor essential volume. These receptor-mapping techniques supplied detailed topographical data that allowed a steric model of the D[ receptor site to be proposed. 

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