Rational design of a series of novel amphipathic cell-penetrating peptides.

A series of novel, amphipathic cell-penetrating peptides was developed based on a combination of the model amphipathic peptide sequence and modifications based on the strategies developed for PepFect and NickFect peptides. The aim was to study the role of amphipathicity for peptide uptake and to investigate if the modifications developed for PepFect peptides could be used to improve the uptake of another class of cell-penetrating peptides. The peptides were synthesized by solid phase peptide synthesis and characterized by circular dichroism spectroscopy. Non-covalent peptide-plasmid complexes were formed by co-incubation of the peptides and plasmids in water solution. The complexes were characterized by dynamic light scattering and cellular uptake of the complexes was studied in a luciferase-based plasmid transfection assay. A quantitative structure-activity relationship (QSAR) model of cellular uptake was developed using descriptors including hydrogen bonding, peptide charge and positions of nitrogen atoms. The peptides were found to be non-toxic and could efficiently transfect cells with plasmid DNA. Cellular uptake data was correlated to QSAR predictions and the predicted biological effects obtained from the model correlated well with experimental data. The QSAR model could improve the understanding of structural requirements for cell penetration, or could potentially be used to predict more efficient cell-penetrating peptides.

Rationalization of the inhibition activity of structurally related organometallic compounds against the drug target cathepsin B by DFT.

A series of organometallic compounds of general formula [(arene)M(PTA)(n)X(m)]Y (arene = eta(6)-C(10)H(14), eta-C(5)Me(5)); M = Ru(ii), Os(ii), Rh(iii) and Ir(iii); X = Cl, mPTA; Y = OTf, PF(6)) have been screened for their cytotoxicity and ability to inhibit cathepsin B in vitro, in comparison to the antimetastatic compound NAMI-A. The Ru and Os analogues and NAMI-A showed similar enzyme inhibition properties (with IC(50) values in the low muM range), whereas the Rh(iii) and Ir(iii) compounds were inactive. In order to build up a rational for the observed differences, DFT calculations of the metal complexes adducts with N-acetyl-l-cysteine-N'-methylamide, a mimic for the Cys residue in the cathepsin B active site, were performed to provide insights into binding thermodynamics in solution. Initial structure-activity relationships have been defined with the calculated binding energies of the M-S bonds correlating well with the observed inhibition properties of the compounds.

Diastereomerically enriched analogues of the water-soluble phosphine PTA. Synthesis of phenyl(1,3,5-triaza-7-phosphatricyclo[3.3.1.1(3,7)]dec-6-yl)methanol (PZA) and the sulfide PZA(S) and X-ray crystal structures of the oxide PZA(O) and [Cp*IrCl(2)(PZA)].

A diastereomerically enriched analogue of 1,3,5-triaza-7-phosphaadamantane (PTA) was obtained by the reaction of PTA lithium salt with benzaldehyde to give the water-soluble derivative phenyl(1,3,5-triaza-7-phosphatricyclo[3.3.1.13,7]dec-6-yl)methanol (PZA, 1) as a mixture of two diastereoisomers. PZA derivatives phenyl(1,3,5-triaza-7-phospha-tricyclo[3.3.1.13,7]dec-6-yl)methanol sulfide [PZA(S), 2] and oxide [PZA(O), 3] were also synthesized. The latter was isolated in the solid state, and the X-ray crystal structure of a single diastereoisomer was obtained. Compound 1 was used as a k1-P monodentate ligand toward iridium(III) moieties, and the piano-stool complex [Cp*IrCl2(PZA)] (4) was obtained as a mixture of diastereoisomers both in solution and in the solid state.