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Abstract Background Haplosclerid marine sponges produce pore forming polyalkylpyridinium salts (poly-APS), which can be used to deliver macromolecules into cells. The aim of this study was to investigate the delivery of DNA, siRNA and lucifer yellow into cells mediated by poly-APS and its potential mechanisms as compared with other lipofection systems (lipofectamine and N4,N9-dioleoylspermine (LipoGen)). DNA condensation was evaluated and HEK 293 and HtTA HeLa cells were used to investigate pore formation and intracellular delivery of cDNA, siRNA and lucifer yellow. Results Poly-APS and LipoGen were both found to be highly efficient DNA condensing agents. Fura-2 calcium imaging was used to measure calcium transients indicative of cell membrane pore forming activity. Calcium transients were evoked by poly-APS but not LipoGen and lipofectamine. The increases in intracellular calcium produced by poly-APS showed temperature sensitivity with greater responses being observed at 12°C compared to 21°C. Similarly, delivery of lucifer yellow into cells with poly-APS was enhanced at lower temperatures. Transfection with cDNA encoding for the expression enhanced green fluorescent protein was also evaluated at 12°C with poly-APS, lipofectamine and LipoGen. Intracellular delivery of siRNA was achieved with knockdown in beta-actin expression when lipofectamine and LipoGen were used as transfection reagents. However, intracellular delivery of siRNA was not achieved with poly-APS. Conclusion Poly-APS mediated pore formation is critical to its activity as a transfection reagent, but lipofection systems utilise distinct mechanisms to enable delivery of DNA and siRNA into cells.

Conformational analyses are presented of several pharmacologically important norditerpenoid alkaloids (NDAs), in crystal and in solution states. Crystal data of 8 NDAs (4 free bases and 4 salts) were obtained, in which crassicauline A, aconitine HCl, and methyllycaconitine HClO4 are reported for the first time. 1D/2D NMR spectroscopies of 7 NDAs (5 free bases and 2 salts) were recorded comprehensively. Crystal conformations of NDAs are described with a revised cyclohexane ring nomenclature. The A/E-rings of NDA-free bases exist in twisted-chair/twistedchair conformations, leading to examples of the 1H NMR effect of steric compression shown in the A-ring. The A/E-rings of NDA salts adopt boat/chair crystal conformations, as does the protonated synthetic [3.3.1]azabicycle in its crystal lattice. However, in aqueous solutions at physiological pH, this protonated analogue adopts a true chair/true chair conformation where the NDA salts retain their twisted boat/twisted chair conformations. [ABSTRACT FROM AUTHOR]