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Substance P and antagonists. Surface activity and molecular shapes.
1Department of Biophysical Chemistry, Biocenter of the University of Basel, Switzerland.
Biochimica Et Biophysica Acta
|November 30, 1990
Summary
Substance P (SP) and its antagonists exhibit distinct molecular properties and surface activities. Antagonists show increased surface activity and adopt extended conformations, unlike SP which folds at physiological concentrations.
Area of Science:
- Biophysical Chemistry
- Neuroscience
- Molecular Pharmacology
Background:
- Substance P (SP) is a neuropeptide involved in various physiological processes.
- Understanding the molecular properties of SP and its antagonists is crucial for drug development.
Purpose of the Study:
- To determine the surface activity, molecular shape, and pK values of SP and three antagonists.
- To investigate the conformational changes of SP and its antagonists in relation to concentration and pH.
Main Methods:
- Gibbs adsorption isotherm measurements.
- Computer modeling for conformational analysis.
- Analysis of surface activity dependence on pH and concentration.
Main Results:
- SP exhibits moderate surface activity and a folded conformation at physiological concentrations, becoming extended at higher densities.
- Antagonists display significantly higher surface activity and adopt an extended conformation across all measured concentrations.
- pK values of charged amino acid side chains were determined, showing shifts compared to free amino acids, explained by Gouy-Chapman theory.
Conclusions:
- Amino acid substitutions in antagonists enhance surface activity and alter molecular conformation compared to SP.
- The distinct conformational behaviors influence the binding of SP and its antagonists to lipid bilayers.
- Surface activity and pK values provide insights into the molecular interactions and potential therapeutic applications of SP antagonists.