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The interaction of nicotine with high density lipoproteins - and IR and Raman study

Cigarette smoking has important effect on plasma lipoprotein metabolism [1] due to the alteration of lipid profile, specially decreasing high density lipoprotein (HDL) level. Nicotine is one of major components of cigarette smoke and its direct interaction with lipoprotein particles was not investigated at molecular level. In our work, the induced structural changes due to the incorporation of nicotine within the particle were studied by IR and Raman spectroscopy in HDL subclass HDL3. Three types of samples were prepared: the solution of native HDL3, and the two solutions in which nicotine was added in the molecular ratio of nicotine / phospholipids, 1: 12 and 1:6. The bands from lipids and amino acid residues were studied directly, while for amide II and amide III protein bands the curve fitting procedure was performed. In IR spectra, the influence of nicotine was observed in lipid bands arising from vibrations of pholipids acyl chain and choline head and in the shape and structure of amide II protein band. Raman spectra are more abundant and produce more information about the system. Some changes where observed in high frequency region of lipid group vibrations, but majority of information was obtained from the differences in the bands arising from vibrations of protein domain: amide III, amino acid residues, presumably aromatic ones, and skeletal vibrations. On the basis of this study it can be deduced that incorporation of nicotine affects the dynamics of lipid monolayer. Nicotine affinity towards aromatic amino acids was observed in the bands of Tyr, Trp and Phe aromatic residues. In addition, nicotine induces downward shifts of some low frequency skeletal bands of proteins. These findings suggest the positioning of nicotine close to protein-lipid interface. References [1] S.Cheland Campbell, R.J. Moffatt and B.A. Stamford, 2008. Smoking and smoking cessation – The relationship between cardiovascular disease and lipoprotein metabolism: A review. Atherosclerosis 201:225-235.

HDL; nicotine; IR spectroscopy; Raman spectroscopy

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