Related Experiment Video
Updated: Jun 1, 2026
10:52
Gramicidin-based Fluorescence Assay; for Determining Small Molecules Potential for Modifying Lipid Bilayer Properties
Published on: October 13, 2010
Isolated gramicidin peptides probed by IR spectroscopy
Anouk M Rijs1, Martin Kabeláč, Ali Abo-Riziq
1FOM Institute for Plasma Physics Rijnhuizen, Edisonbaan 14, 3439 MN Nieuwegein, The Netherlands. A.M.Rijs@Rijnhuizen.nl
Summary
This study used infrared (IR) spectroscopy to analyze gramicidin peptides in the gas phase. Results reveal a helical structure, similar to condensed-phase forms, aiding in understanding peptide conformation.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Biophysics
Background:
- Gramicidin peptides are important antimicrobial agents.
- Understanding their gas-phase structure is crucial for elucidating their mechanism of action.
- Previous studies have primarily focused on condensed-phase structures.
Purpose of the Study:
- To investigate the gas-phase structure of neutral gramicidin A and C peptides.
- To analyze intramolecular interactions and conformational preferences.
- To compare gas-phase structures with known condensed-phase conformations.
Main Methods:
- Double-resonant infrared (IR)/ultraviolet (UV) ion-dip spectroscopy was employed.
- IR spectra were recorded in the 1000-1800 cm(-1) and 2700-3750 cm(-1) regions.
- Ab initio quantum chemical calculations were performed to support spectral interpretation.
Main Results:
- Experimental IR spectra provided insights into local intramolecular interactions.
- Analysis of amide group vibrations (NH stretch, C=O stretch, NH bend) indicated a helical structure.
- The observed gas-phase helical structure is comparable to condensed-phase gramicidin structures.
Conclusions:
- Gramicidin peptides adopt a helical conformation in the gas phase.
- The findings suggest structural similarities between gas-phase and condensed-phase gramicidins.
- Using heavier carrier gases may enhance spectral resolution for large neutral molecules.
Related Concept Videos
01:26Spectroscopy of Carboxylic Acid Derivatives
Infrared spectroscopy is primarily used to determine the types of bonds and functional groups. In carboxylic acid derivatives, a typical carbonyl bond absorption is observed around 1650–1850 cm−1. For esters, the absorption is recorded at around 1740 cm−1, while acid halides show the absorption at about 1800 cm−1. Another acid derivative, the acid anhydrides, exhibit two carbonyl absorption around 1760 cm−1 and 1820 cm−1, arising from the symmetrical and unsymmetrical carbonyl vibration.
In the...
In the...
01:23Inhibitors of Gram-positive Cell Wall Synthesis
Bacterial cell walls are typically rigid structures composed mainly of peptidoglycan, a mesh-like polymer that provides mechanical strength and maintains cell shape. The synthesis of peptidoglycan is a crucial process in bacterial growth and serves as a primary target for many antibiotics.Mechanism of Action of Beta-Lactam AntibioticsBeta-lactam antibiotics, such as penicillin, inhibit peptidoglycan synthesis in actively growing cells. These antibiotics share a characteristic four-membered...
01:09Infrared (IR) Spectroscopy: Overview
When electromagnetic radiation passes through a material, atoms or molecules transition from a lower to a higher energy state by absorbing radiation corresponding to the energy difference between the two states. The absorption of infrared (IR) radiation causes transitions between vibrational energy levels in a molecule. Therefore, IR spectroscopy is a useful analytical tool for determining the molecular structure of molecules.
Different compounds display unique properties due to their...
Different compounds display unique properties due to their...
01:28IR and UV–Vis Spectroscopy of Carboxylic Acids
In IR spectroscopy of carboxylic acids, the C=O bond shows a characteristic band between 1710 and 1760 cm⁻¹, and the O–H bond exhibits a broad band between 2500 and 3300 cm⁻¹.
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency, 1710 cm−1. The C=O bond of the...
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency, 1710 cm−1. The C=O bond of the...
00:55IR Spectrum Peak Intensity: Amount of IR-Active Bonds
When infrared radiation is passed through a molecule, absorption occurs if the molecule's vibration leads to a substantial change in its bond dipole moment. Transitions between vibrational energy levels, typically corresponding to infrared frequencies (4000–400 cm−1), allow absorption if the vibration significantly alters the dipole moment, making the molecule infrared active. The molecular bonds have different stretching and bending vibrations, resulting in various peaks with varying...