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Enantiodiscrimination between an N ‐Acetyl‐ L ‐cysteine SAM and Proline: An In Situ Spectroscopic and Computational Study
Author(s) -
Bieri Marco,
Bürgi Thomas
Publication year - 2006
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200500474
Subject(s) - chemistry , deprotonation , density functional theory , molecule , protonation , monolayer , cysteine , attenuated total reflection , diastereomer , proline , infrared spectroscopy , stereochemistry , spectroscopy , crystallography , computational chemistry , amino acid , organic chemistry , ion , enzyme , biochemistry , physics , quantum mechanics
10.1002/cphc.200500474.abs A combination of attenuated total reflection infrared (ATR‐IR) and modulation excitation spectroscopy (MES) is used to study the enantiodiscriminating interactions between proline and a chiral, self‐assembled monolayer (SAM) of N ‐acetyl‐ L ‐cysteine on gold. The N ‐acetyl‐ L ‐cysteine SAM consists of a mixture of protonated and deprotonated molecules. Whereas both species are influenced by adsorbed proline, only the deprotonated molecules are involved in enantiodiscrimination. Density functional theory (DFT) calculations reveal that electrostatics dominates the interaction between the two molecules. By modulating the absolute configuration of proline over the chiral SAM, and a subsequent phase‐sensitive detection of the periodically varying signals in the ATR‐IR spectra, the small spectral differences between the diastereomeric complexes are spotted. The resulting difference spectrum is in qualitative agreement with the spectrum predicted by the DFT calculations.