In this study, the charge selectivity of staphylococcal ␣-hemolysin (␣HL), a bacterial pore-forming toxin, is manipulated by using cyclodextrins as noncovalent molecular adapters. Anionselective versions of ␣HL, including the wild-type pore and various mutants, become more anion selective when ␤-cyclodextrin (␤CD) is lodged within the channel lumen. By contrast, the negatively charged adapter, hepta-6-sulfato-␤-cyclodextrin (s7␤CD), produces cation selectivity. The cyclodextrin adapters have similar effects when placed in cation-selective mutant ␣HL pores. Most probably, hydrated Cl ؊ ions partition into the central cavity of ␤CD more readily than K ؉ ions, whereas s7␤CD introduces a charged ring near the midpoint of the channel lumen and confers cation selectivity through electrostatic interactions. The molecular adapters generate permeability ratios (P K؉/PCl؊) over a 200-fold range and should be useful in the de novo design of membrane channels both for basic studies of ion permeation and for applications in biotechnology.

A new, moderately hydrophobic, single-isomer charged cyclodextrin, the sodium salt of heptakis(2,3-diacetyl-6sulfato)--cyclodextrin, has been synthesized and used to separate a variety of neutral, weak acid, strong base, weak base, and zwitterionic racemic enantiomers in low-pH and high-pH background electrolytes. Separation selectivity for the netural analytes rapidly decreases as the concentration of heptakis(2,3-diacetyl-6-sulfato)--cyclodextrin increases. For charged analytes, selectivity can increase, decrease, or pass a maximum, depending on the numeric values of the respective complexation constants and ionic mobilities. In addition to separation selectivity, the extent of peak resolution that can be realized strongly depends on the magnitude of the dimensionless electroosmotic flow. Heptakis(2,3-diacetyl-6-sulfato)--cyclodextrin proved to be a broadly applicable chiral resolving agent.

The copper(I) complex [Cu(C18(6)tren)]Br 1 (C18(6)tren = tris(2-dioctadecylaminoethyl)amine) which exhibits a good stability towards aerobic conditions is a versatile, highly reactive and recyclable catalyst for the Huisgen cycloaddition of azides with terminal or internal alkynes and is a useful catalyst for the preparation of "click" dendrimers.

A new, hydrophilic, single-isomer charged cyclodextrin, the sodium salt of hepta-6-sulfato-β-cyclodextrin has been synthesized, characterized, and used for the capillary electrophoretic separation of the enantiomers of numerous noncharged, acidic, basic, and zwitterionic analytes. Hepta-6-sulfato-β-cyclodextrin proved to be a much stronger complexing agent for all the analytes tested, in both low-pH and high-pH background electrolytes, than the previously synthesized, moderately hydrophobic heptakis(2,3-diacetyl-6-sulfato)-β-cyclodextrin. The separation selectivities of the two single-isomer, differently functionalized charged cyclodextrins often proved to be complementary. In agreement with the predictions of the charged resolving agent migration model, separation selectivity for the noncharged analytes decreased as the concentration of hepta-6-sulfato-β-cyclodextrin was increased. For acidic, basic, and zwitterionic analytes, selectivity could increase, decrease, or pass a maximum, depending on the binding strength of the enantiomers and ionic mobilities of both the complexed and noncomplexed forms of the enantiomers.

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