FTIR and Theorical Study of the Interaction of Nicotinamide and Picolinamide with Phospholipids

ANA BORBA, ANDREA GÓMEZ-ZAVAGLIA, FABIANA LAIRIÓN, ANÍBAL DISALVO, RUI FAUSTO.

Luso, Portugal

Congreso; 8º Encontro Nacional da Sociedade Portuguesa de Química.; 2007

Sociedade Portuguesa de quimica

Lipid bilayers play a key role in living cells because they are the main constituents of the cell membranes, separating the cells from the outside environment. Other elements of the cell membrane, such as ion channel forming proteins or transmembrane helices of signal transducting proteins are embedded in the environment of such bilayers [1]. Phospholipids are important constituents of biological membranes and their interactions with bioactive species are then of fundamental importance for living beings. In this work, the interaction of phospholipids (DMPC, 1,2-dimyristoyl-sn-glycero-3-phosphocholine; PC ether, 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine; DMPE, 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine and PE ether, 1,2-di-O-tetradecyl-sn-glycero-3-phospho-ethanolamine) with two well known [2,3] bioactive isomers of pyridinecarboxamide, picolinamide (PA) and Nicotinamide (NA), was studied by FTIR spectroscopy and quantum chemical calculations. Lipids were hydrated in solutions of NA and PA (100 and 500 mM) heated above the transition temperature and gently agitated during 15 min to produce multilamellar vesicles. After that, IR spectra were registered in a Bomem MB104 Fourier-transform spectrometer, fited with a Zn/Se beam splitter and a DTGS detector (with resolution: 2 cm−1). Dipole potential (ΨD) was determined in monolayers formed on an air–water interface by spreading chloroform solutions of the different lipids over an aqueous subphase (KCl 1 mM) with or without NA or PA. Theoretical calculations were performed with the GAUSSIAN 03 program, at Hartree-Fock level of theory, using the split valence 3-21G basis set. The results show that PA and NA interact in different extent with the phosphate groups and do not interact with the carbonyl moieties. The interaction of both NA and PA with the studied ethers confirmed this observation. Figure 1 – Structures of PA, NA and the structures of phospholipids used in this study. 1. P.Jedlovszky, L.Pártay, M.Mezei, J. Mol. Liq. 131–132 (2007) 225. 2. T.Kawabata, T.Ogino, M.Mori, M.Awai, Acta Pathol. Jpn., 42 (1992) 469. 3. A.Olsen, L.Liu, N.Ghaderi, A.Johns, M.Hatcher, L.Mueller, J. Am. Chem. Soc., 125 (2003) 10125. Acknowledgements: This work was supported by FCT (POCTI/QUI/2004: 59019 and 58937), Instituto de Investigação Interdisciplinar of the University of Coimbra (III/BIO/40/2005) and the GRICES/SECyT (Project GRICES/SECyT-000813//PO-PA04-EVI/001). A.B. acknowledges FCT the Ph.D. grant (SFRH/BD/21543/2005).