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Determination of the Gas-phase Acidities of Oligopeptides
Published on: June 24, 2013
The gas-phase structure of alanine
Susana Blanco1, Alberto Lesarri, Juan C López
1Contribution from the Grupo de Espectroscopía Molecular (GEM), Departamento de Química Física y Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid, Spain.
Journal of the American Chemical Society
|September 16, 2004
Summary
Researchers used laser-ablation molecular-beam Fourier transform microwave spectroscopy to study neutral alanine. They determined the structures of two stable alanine conformers, revealing nonplanar backbones and distinct hydrogen bonding patterns for each.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Molecular Structure Determination
Background:
- Alanine is a fundamental amino acid with implications in biochemistry and drug design.
- Understanding alanine's conformational landscape is crucial for predicting its behavior in biological systems.
- Previous studies have lacked detailed experimental structural data for neutral alanine conformers.
Purpose of the Study:
- To experimentally determine the precise molecular structures of the most stable neutral alanine conformers.
- To investigate the hydrogen bonding interactions stabilizing these conformers.
- To assign and confirm conformer structures using high-resolution spectroscopic data.
Main Methods:
- Laser-ablation molecular-beam Fourier transform microwave spectroscopy (LA-MB-FTMW) was employed to obtain high-resolution rotational spectra.
- Isotopically labeled alanine species ((15)N, (13)C, D) were studied to aid spectral assignment.
- Nuclear quadrupole coupling hyperfine structures were resolved and analyzed.
Main Results:
- The rotational spectra of two stable alanine conformers were observed and assigned.
- Experimental structures were determined for both conformers using r(s) and r(0) methods, revealing nonplanar backbones.
- Conformer I exhibits a cis COOH group with a bifurcated hydrogen bond; Conformer IIa has a trans COOH group stabilized by an O-H...N hydrogen bond.
Conclusions:
- The study provides the first experimental determination of independent structures for two neutral alanine conformers.
- The resolved nuclear quadrupole coupling structures unambiguously confirm the conformer assignments.
- Detailed insights into alanine's conformational preferences and stabilizing interactions were obtained.
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