The introduction of aminoalkylamino and guanidinoalkylamino substituents on the primary side of beta- and gamma-cyclodextrin (CDs) resulted in a series of novel compounds that were extensively characterized by NMR spectroscopy and mass spectrometry. Bromination of the primary side of beta- and gamma-CD, and reaction with neat alkylene diamines at a pressure of 7 atm afforded aminoalkylamino derivatives that were then guanylated at the primary amino group to give the corresponding guanidinoalkylamino-CDs. These compounds are water soluble and display pK(a) values that allow them to be mostly protonated at neutral pH; for example, pK(a(1)) approximately 6.4 and pK(a(2)) approximately 9.5 for the aminoethylamino-beta-CD and pK(a(1)) approximately 7.8 and pK(a(2)) approximately 11.0 for the guanidinoethylamino-beta-CD. The title CDs are rigid, cyclic alpha-D-glucopyranose oligomers (heptamers or octamers) with branches that resemble lysine and arginine side chains that enable multiple interactions with suitable substrates. Thus, they bear similarities to known cell-penetrating peptides. Indeed, the compounds were found to cross the membranes of HeLa cells and penetrate inside the cytoplasm quickly, the guadinylated ones within 15 min, as shown by fluorescence microscopy using fluorescein-labeled derivatives. The toxicity of the compounds, measured by performing MTT tests, ranged from 50 to 300 microM. Furthermore, some of the aminated CDs could facilitate the transfection of DNA expressing the green fluorescent protein (GFP) in HEK 293T cells, with effectiveness comparable to the commercial agent Lipofectamine 2000. Circular dichroism, atomic force microscopy and electrophoresis experiments confirmed the strong interaction of the compounds with DNA. Because of their carbohydrate, non-peptide nature the title compounds are not anticipated to be enzymatically labile or immunogenic, and thus they fulfill many of the criteria for non-hazardous transport vectors in biological and pharmaceutical applications.

Per(6-guanidino-6-deoxy)-cyclodextrins , and are novel derivatives, resulting from homogeneous introduction of the guanidino group at the primary side of alpha-, beta- and gamma-cyclodextrins. The products were obtained from the corresponding amino derivatives, as direct guanidinylation of the known bromo-cyclodextrins provided mixtures. The new compounds were fully characterized by NMR spectroscopy and other analytical methods, and their interaction with guest molecules was studied. Strong complexation with 4-nitrophenyl phosphate () disodium salt was observed (K(binding) approximately 5 x 10(4) M(-1)), whereas the non-phosphorylated substrate nitrobenzene () formed a very weak complex. 2D ROESY spectra revealed cavity inclusion in both cases, however the orientation of was opposite to that of , such that the phosphate group is oriented toward the primary side facing the guanidine groups. The strong affinity of towards the phosphorylated guest suggested that interaction with DNA was possible. The new compounds were found to completely inhibit the migration of ultra pure calf thymus DNA during agarose gel electrophoresis, whereas no effects were observed with guanidine alone or with the plain cyclodextrins. Further, the condensation of DNA into nanoparticles in the presence of was demonstrated by atomic force microscopy, confirming strong electrostatic interaction between the biopolymer and the multicationic products . The strong guanidine-phosphate interactions between and DNA were therefore attributed to the clustering of the guanidine groups in the primary area of the cyclodextrin. Cavity effects could not be assessed.

We compared the abilities of structurally related cationic cyclodextrins to inhibit Bacillus anthracis lethal toxin and Staphylococcus aureus ␣-hemolysin. We found that both ␤-and ␥-cyclodextrin derivatives effectively inhibited anthrax toxin action by blocking the transmembrane oligomeric pores formed by the protective antigen (PA) subunit of the toxin, whereas ␣-cyclodextrins were ineffective. In contrast, ␣-hemolysin was selectively blocked only by ␤-cyclodextrin derivatives, demonstrating that both symmetry and size of the inhibitor and the pore are important.Previously, we proposed a novel approach for the discovery of inhibitors of pore-forming toxins that involves the blockage of the pores using molecules with comparable dimensions and the same symmetry as the target pores. It allows for the identification of lead compounds faster and significantly more cheaply in comparison with the existing industry standards. First, this approach was successfully tested on anthrax lethal toxin (LeTx), which plays a key role in anthrax infection. The toxin was disabled by the blockage of the pore formed by protective antigen (PA 63 ), an essential component of anthrax toxin, by rationally designed compounds. Based on the 7-fold symmetry of the PA 63 pore, we synthesized and tested cyclic molecules that had 7-fold symmetry using ␤-cyclodextrin (␤-CD) as a starting molecule (Fig. 1). The discovered inhibitors of anthrax toxin were successfully tested in vitro and in vivo (1-5, 7, 10). The broader applicability of this approach was demonstrated using as targets two other toxins that form transmembrane pores with 7-fold symmetry: ␣-hemolysin (␣-HL) of Staphylococcus aureus (2, 11) and ε-toxin produced by Clostridium perfringens (unpublished data).To investigate how the structural features of the pore blockers affect their activities, we evaluated the ability of structurally related derivatives of ␣-, ␤-, and ␥-cyclodextrins to inhibit the cytotoxic activities of anthrax lethal toxin (LeTx) and staphylococcal ␣-HL as well as to block the ion current through the channels formed by PA 63 and ␣-HL in planar lipid membranes.

Ruthenium(II) pyridylimine complexes are explored for their potential as units that might be incorporated into electronic or photonic arrays. The complexes [Ru(bipy)2(L)][PF6]2 (1) and [Ru(tpy)(L)Cl][BF4] (2) with L = phenylpyridin-2-ylmethylene-amine are synthesized and fully characterised using X-ray diffraction analysis and (2D) NMR spectroscopy. 1 displays emission in the far-red area of the spectrum at room temperature. The emission is significantly shifted to longer wavelength with respect to [Ru(bpy)3]2+ indicating that the lowest MLCT state is localised on the pyridylimine ligand. 2 is non-emissive at room temperature and at 77 K.

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