Raman spectroscopy study of the interaction of 3,5,3′-triiodo-L-thyronine with phosphatidylglycerol lipid bilayers

• Published in: Journal of Raman spectroscopy 2015-03, Vol.46 (3), p.302-308
• Main Authors: Sosa Morales, Marcelo C., Juárez, Ana C., Álvarez, Rosa M. S.
• Format: Article
• Language: English
• Subjects: anionic membranes; Biomolecules; Hormones; Lipids; Membranes; Penetration; Phases; phospholipids; Raman spectroscopy; Spectra; Vesicles; vibrational analysis
• ISSN: 0377-0486; 1097-4555
• DOI: 10.1002/jrs.4639

A Raman spectroscopic study of anionic model membranes and their structural alterations exerted by a relatively small biomolecule, such as the hormone 3,5,3′‐triiodo‐L‐thyronine (T3), is presented. Spectral differences between pure dipalmitoylphosphatidylglycerol (DPPG) multilamellar vesicles and DPPG–T3 mixture and between pure dilauroylphosphatidylglycerol (DLPG) and DLPG–T3 mixture were evaluated in order to determine the response of lipid membranes in gel and liquid‐crystalline phases to the hormone incorporation. Density functional theory (DFT) calculations support the band analysis of the complex 1150–1050 cm−1 Raman region. Geometry optimizations and vibrational behaviors of a model charged molecule that mimics the phosphatidylglycerol lipid moiety in solvated state were taken into account for the spectral interpretation of this specific region. The anionic nature of the lipid polar head plays an important role in the interaction with the hormone, as is evidenced by the CO and PO2− stretching bands. In addition, the differential penetration of T3 into the hydrophobic region of the membranes shows to be dependent on the lipid phase. The spectral data were compared with those previously obtained for zwitterionic membranes. Copyright © 2015 John Wiley & Sons, Ltd. Interactions of 3,5,3′‐triiodo‐L‐thyronine with dipalmitoylphosphatidylglycerol and dilauroylphosphatidylglycerol vesicles in gel and liquid‐crystalline phases, respectively, were studied by Raman spectroscopy. Spectral evidence that the hormone achieves a restricted penetration into the hydrophobic region of the membrane in fluid state is presented here. In addition, the vibrational behavior of lipids in the ordered phase indicates that most of the hormone molecule remains anchored in the surface region of the bilayer due to the high density packing and the its anionic nature.