JABERI, AKH, J. A. H. AL SAEDI, MARIA MERNEA, L. PETRESCU, O. CĂLBOREAN, I. VASILE, and DF MIHĂILESCU. "LIPOPOLYSACCHARIDES ASSOCIATION ON THE SURFACE OF A SILICON CRYSTAL ADDRESSED BY THz SPECTROSCOPY AND MOLECULAR MODELLING." Romanian Journal of Biophysics 29, no. 1 (2019).
Astract.
Gram-negative bacteria lipopolysaccharides (LPS) are lipids with a chemical
structure comprising a lipidic region with several hydrocarbonate chains and a large saccharide
region. Due to their structure, LPS can associate through hydrophobic forces, but also can dissolve in
water. Here we investigated the association of LPS molecules on the surface of a silicon crystal by
terahertz (THz) spectroscopy. We measured the THz absorption of LPS molecules directly deposited
on the crystal or deposited on the crystal coated with a CaCl2 solution. Resulting spectra present a
non-linear increase of THz absorption, with two absorption shoulders at 1.05 THz (~35 cm–1
) and
1.37 THz (~45 cm–1
). The presence of the CaCl2 solution does not influence the shoulders
localization, suggesting a similar association of LPS molecules in both situations. Based on the
comparison with previous THz studies on phospholipid bilayers, we suggested a layer ordering of
LPS molecules in our samples that was validated through molecular modelling methods. We
modelled LPS monolayers and simulated the THz spectra by normal modes analysis (NMA) and
molecular dynamics (MD). The NMA spectrum of a LPS monolayer resulted in agreement with
experiments, allowing us to validate the proposed LPS layer organization and the spectra simulation
method.
For full paper see https://www.rjb.ro/wp-content/uploads/Mernea_4_F.pdf
… LPS molecules (2 mg/mL) were dissolved into a 7:3
chloroform-methanol mixture [16]. THz spectra were recorded using a TPS spectra 3000 spectrometer (TeraView Ltd., United Kingdom) in attenuated total reflection (ATR) setup under continuous nitrogen
purge …
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