Nucleic Acids Research Advance Access originally published online on June 26, 2009
Nucleic Acids Research 2009 37(15):5197-5207; doi:10.1093/nar/gkp543
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Nucleic Acids Research, 2009, Vol. 37, No. 15 5197-5207
© 2009 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Structural characterization of cationic lipid–tRNA complexes
1Department of Chemistry-Biology, University of Québec at Trois-Rivières, C.P. 500, Trois-Rivières, Québec, G9A 5H7 and 2Department of Physics and Atmospheric Science, Sir James Dunn Building, Dalhousie University, Lord Dalhousie Drive, Halifax, NS B3H 3J5, Canada
*To whom correspondence should be addressed. Tel: +1 819 376 5011. Ext. 3310; Fax: +1 819 376 5084; Email: tajmirri{at}uqtr.ca
Received May 14, 2009. Revised June 8, 2009. Accepted June 9, 2009.
Despite considerable interest and investigations on cationic lipid–DNA complexes, reports on lipid–RNA interaction are very limited. In contrast to lipid–DNA complexes where lipid binding induces partial B to A and B to C conformational changes, lipid–tRNA complexation preserves tRNA folded state. This study is the first attempt to investigate the binding of cationic lipid with transfer RNA and the effect of lipid complexation on tRNA aggregation and condensation. We examine the interaction of tRNA with cholesterol (Chol), 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), dioctadecyldimethylammoniumbromide (DDAB) and dioleoylphosphatidylethanolamine (DOPE), at physiological condition, using constant tRNA concentration and various lipid contents. FTIR, UV-visible, CD spectroscopic methods and atomic force microscopy (AFM) were used to analyze lipid binding site, the binding constant and the effects of lipid interaction on tRNA stability, conformation and condensation. Structural analysis showed lipid–tRNA interactions with G–C and A–U base pairs as well as the backbone phosphate group with overall binding constants of KChol = 5.94 (± 0.8) x 104 M–1, KDDAB = 8.33 (± 0.90) x 105 M–1, KDOTAP = 1.05 (± 0.30) x 105 M–1 and KDOPE = 2.75 (± 0.50) x 104 M–1. The order of stability of lipid–tRNA complexation is DDAB > DOTAP > Chol > DOPE. Hydrophobic interactions between lipid aliphatic tails and tRNA were observed. RNA remains in A-family structure, while biopolymer aggregation and condensation occurred at high lipid concentrations.