Cationic lipids and cationic ligands induce DNA helix denaturation: detection of single stranded regions by KMnO4 probing

[摘要]

Cationic lipids and cationic polymers are widely used in gene delivery. Using 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) as a cationic lipid, we have investigated the stability of the DNA in DOTAP:DNA complexes by probing with potassium permanganate (KMnO₄). Interestingly, thymidines followed by a purine showed higher susceptibility to cationic ligand-mediated melting. Similar studies performed with other water-soluble cationic ligands such as polylysine, protamine sulfate and polyethyleneimine also demonstrated melting of the DNA but with variations. Small cations such as spermine and spermidine and a cationic detergent, cetyl trimethylammonium bromide, also rendered the DNA susceptible to modification by KMnO₄. The data presented here provide direct proof for melting of DNA upon interaction with cationic lipids. Structural changes subsequent to binding of cationic lipids/ligands to DNA may lead to instability and formation of DNA bubbles in double-stranded DNA.

[学科分类] 生物化学/生物物理

[关键词] Cationic lipid;DNA condensation;DNA unwinding;KMnO4 probing;Transfection;Cationic lipid:DNA complex;CD;circular dichroism;CLDC;cationic lipid:DNA complex;CTAB;cetyl trimethylammonium bromide;DC-Chol;3β-[N-(N′;N′-dimethylaminoethane)-carbamoyl]cholesterol;DDAB;dimethyldioctadecylammonium bromide;DMRIE-C;1;2-dimyristyloxypropyl-3-dimethyl-hydroxy ethyl ammonium bromide-cholesterol;DOPC;1;2-dioleoyl-sn-glycero-3-phosphocholine;DOPE;L-α-dioleoyl phosphatidylethanolamine;DOTAP;1;2-dioleoyl-3-trimethylammonium-propane;DOTMA;N-[1-(2;3-dioleyloxy)propyl]-N;N;N-trimethylammonium chloride;FTIR;Fourier transform infrared;N/P charge ratio;positive charge of tertiary ammonium/negative charge of phosphate