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Related Concept Videos

Ligand Binding and Linkage00:49

Ligand Binding and Linkage

Allosteric proteins have more than one ligand binding site; the binding of a ligand to any of these sites influences the binding of ligands to the other sites. When a protein is allosteric, its binding sites are called coupled or linked.  In the case of enzymes, the site that binds to the substrate is known as the active site and the other site is known as the regulatory site. When a ligand binds to the regulatory site, this leads to conformational changes in the protein that can influence the...
Conformations of Cyclohexane02:11

Conformations of Cyclohexane

Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
Chair Conformation of Cyclohexane02:02

Chair Conformation of Cyclohexane

The chair conformation is the most stable form of cyclohexane due to the absence of angle and torsional strain. The absence of angle strain is a result of cyclohexane’s bond angle being very close to the ideal tetrahedral bond angle of 109.5° in its chair conformer. Similarly, the torsional strain is also absent owing to the perfectly staggered arrangement of bonds.
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
Ligand Binding and Linkage00:49

Ligand Binding and Linkage

Allosteric proteins have more than one ligand binding site; the binding of a ligand to any of these sites influences the binding of ligands to the other sites. When a protein is allosteric, its binding sites are called coupled or linked.  In the case of enzymes, the site that binds to the substrate is known as the active site and the other site is known as the regulatory site. When a ligand binds to the regulatory site, this leads to conformational changes in the protein that can influence the...
GPCR Desensitization01:12

GPCR Desensitization

G protein-coupled receptor (GPCR) signaling plays a crucial role in cell functioning. GPCR desensitization is an equally essential process. It allows cells to respond to changing environments and regain sensitivity to new stimuli while preventing unnecessary stimulation when no longer needed. Prolonged exposure to stimuli leads to GPCR desensitization. It involves blocking the receptors from binding and activating additional G proteins. This inhibits activation of downstream effectors, thereby...
Opioid Receptors: Overview01:22

Opioid Receptors: Overview

Opioid receptors, including the mu (μ, MOR), delta (δ, DOR), and kappa (κ, KOR) types, belong to the rhodopsin family of G protein-coupled receptors. These receptors are located throughout the central and peripheral nervous systems and in non-neuronal tissues such as macrophages and astrocytes. Opioid receptor ligands can be categorized into agonists or antagonists. Highly selective agonists include [d-Ala2, MePhe4, Gly(ol)5]-enkephalin or DAMGO for MOR, [D-Pen2, D-Pen5]-enkephalin or DPDPE for...

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Related Experiment Video

Updated: Jul 26, 2026

Development of Inhibitors of Protein-protein Interactions through REPLACE: Application to the Design and Development Non-ATP Competitive CDK Inhibitors
10:33

Development of Inhibitors of Protein-protein Interactions through REPLACE: Application to the Design and Development Non-ATP Competitive CDK Inhibitors

Published on: October 26, 2015

Conformationally readdressed CCK-B/delta-opioid peptide ligands

G V Nikiforovich1, S A Kolodziej, B Nock

  • 1Center for Molecular Design, Washington University, School of Medicine, St. Louis, MO 63130, USA.

Biopolymers
|October 1, 1995
PubMed
Summary

Researchers modified cholecystokinin (CCK) peptides to create analogues that selectively bind to CCK-B or delta-opioid receptors. Minimal structural changes successfully redirected peptide interactions to a different receptor system.

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Structure-Guided Design and Development of Novel Cyclophilin A Inhibitors and Ganoderiol-F Derivatives: An In-Silico Approach
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Structure-Guided Design and Development of Novel Cyclophilin A Inhibitors and Ganoderiol-F Derivatives: An In-Silico Approach

Published on: June 23, 2026

Area of Science:

  • Medicinal Chemistry
  • Molecular Pharmacology
  • Neuroscience

Background:

  • Cholecystokinin (CCK) peptides play roles in various physiological processes.
  • Modulating CCK receptor activity is a target for therapeutic interventions.
  • Understanding peptide-receptor interactions is crucial for drug design.

Purpose of the Study:

  • To design and synthesize novel peptide analogues with selective binding affinities.
  • To investigate the structural modifications required for redirecting peptide interactions from CCK-B to delta-opioid receptors.
  • To explore the potential of minimal chemical changes in altering peptide pharmacology.

Main Methods:

  • Peptide synthesis of cyclic and linear analogues based on a CCK-related sequence.
  • Molecular modeling to predict low-energy conformers and receptor compatibility.
  • In vitro binding assays (Ki and IC50 values) to determine receptor selectivity.

Main Results:

  • Cyclic analogue 1a demonstrated high affinity for delta-opioid receptors (Ki = 4.5 nM) and low affinity for mu-opioid receptors (>5000 nM).
  • Analogue 1a showed selectivity for CCK-A receptors (IC50 = 1.6 nM) over CCK-B receptors (>10,000 nM).
  • Minimal structural modifications, including cyclization and sulfur-to-methyl group replacement, altered receptor binding profiles.

Conclusions:

  • It is possible to redirect peptide interactions from CCK-B receptors to delta-opioid receptors through subtle structural modifications.
  • Conformational changes induced by minimal chemical alterations are key to achieving this receptor redirection.
  • This strategy offers a novel approach for developing selective modulators of different receptor systems.