Related Experiment Video
Updated: Aug 25, 2026

Preparation and In Vivo Use of an Activity-based Probe for N-acylethanolamine Acid Amidase
Published on: November 23, 2016
Structure-activity study of the ORL1 antagonist Ac-Arg-D-Cha-Qaa-D-Arg-D-p-ClPhe-NH2
Sylvia Van Cauwenberghe1, Frédéric Simonin, Jérôme Cluzeau
1Eenheid Organische Chemie, Vrije Universiteit Brussel, 2, Pleinlaan, B-1050, Brussels, Belgium.
Abstract:
The structure-activity requirements of the ORL1 antagonist Ac-Arg-D-Cha-Qaa-D-Arg-D-p-ClPhe-NH(2) 4 were investigated by varying the position, structure, and charge of the Arg residues. Attempts to abridge the peptide by removal of the Arg, D-Cha, and D-p-ClPhe residues abolished affinity for the ORL1 receptor, whereas deletion of the acetamido N-terminus maintained receptor affinity and selectivity. This series of analogues has provided an improved potent and selective ORL1 receptor antagonist, Ac-Cit-D-Cha-Qaa-D-Arg-D-p-ClPhe-NH(2).
Related Concept Videos
Indirect-Acting Cholinergic Agonists: Chemistry and Structure-Activity Relationship
Reversible inhibitors display short to medium durations of action. Short-acting agents include simple alcohols with...
Direct-Acting Cholinergic Agonists: Chemistry and Structure-Activity Relationship
The direct-acting...
Cholinergic Antagonists: Chemistry and Structure-Activity Relationship
Indirect-Acting Cholinergic Agonists: Mechanism of Action
Reversible inhibitors like edrophonium bind to a specific part of the enzyme called the anionic catalytic site. They form noncovalent bonds, which means they are not strongly attached to the enzyme. This creates a temporary and less stable enzyme–inhibitor complex, leading to...
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3
Adrenergic Agonists: Chemistry and Structure-Activity Relationship
Aromatic ring substitutions: Substituting the aromatic ring with –OH groups at positions 3 and 4 yields catecholamines (e.g., epinephrine), which have a high affinity for adrenoceptors. Hydrogen bonding between –OH groups and receptors enhances adrenergic activity.
Separation of the aromatic...

