Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates

The synthesis of new calix[4]arenes adopting a cone stereoisomeric form bearing two or four azide fragments on the upper rim and water-soluble triazolyl amphiphilic receptors with two or four polyammonium headgroups via copper-catalyzed azide–alkyne cycloaddition reaction has been performed for the first time. It was found that the synthesized macrocycles form stable aggregates with hydrodynamic diameters between 150–200 nm and electrokinetic potentials about +40 to +60 mV in water solutions. Critical aggregation concentration (CAC) values were measured using a micelle method with pyrene and eosin Y as dye probes. The CAC values of tetraalkyl-substituted macrocycles 12a,b (5 µM for both) are significantly lower than those for dialkyl-substituted macrocycles 10a,b (790 and 160 µM, respectively). Premicellar aggregates of macrocycles 10a,b and 12a,b with the dye eosin Y were used for nucleotides sensing through a dye replacement procedure. It is unusual that disubstituted macrocycles 10a,b bind more effectively a less charged adenosine 5'-diphosphate (ADP) than adenosine 5'-triphosphate (ATP). A simple colorimetric method based on polydiacetylene vesicles decorated with 10b was elaborated for the naked-eye detection of ADP with a detection limit of 0.5 mM.

J- and H-Aggregates of Porphyrins with Surfactants: Fluorescence, Stopped Flow and Electron Microscopy Studies

The interaction of cationic surfactants such as CTAB (cetyl trimethyl ammonium bromide) with tetrakis-(4-sulfonato phenyl) porphine ( H 4 TPPS 2−), a dianion, leads to the formation of two premicellar aggregates of porphyrin when [CTAB] is below CMC (critical micelle concentration) and a micellized monomer when [CTAB] is above CMC. The premicellar aggregates are labeled as J- and H-aggregates because of their characteristic spectroscopic properties. Simple inorganic cations such as K +, Ba 2+, Ca 2+ and Zr 4+ also induce the formation of the J-aggregate but not of the H-aggregate. The formation of the J-aggregate is preceded by kinetic intermediates, while no intermediate was observed prior to the formation of the H-aggregate. The rate of formation of the H-aggregate was faster than that of the J-aggregate. The fluorescence depolarization (anisotropy) properties of the monomer and the H- and J-aggregates were studied and compared. The size and structure of the J-aggregate were examined by transmission electron microscopy (TEM). The structure of the J-aggregate reveals a fiber-like (linear stacking) or domain-like (helical stacking) arrangement of the porphyrin molecules.

Fluorescence Quenching of Polycyclic Aromatic Hydrocarbons by Cetylpyridinium Bromide: Discrimination between Alternant and Nonalternant Hydrocarbons

Molecules of polycyclic hydrocarbons (PAHs) that contain between two and five rings undergo quenching processes in the presence of cetylpyridinium bromide (CPB), which can act as quencher and as surfactant. The CPB concentration and the nature of the PAHs notably influence the inhibition mechanisms of fluorescence. Dynamic quenching is predominant for all hydrocarbons in solutions in which CPB is found in the form of monomers. When the quencher forms premicellar aggregates, fluoranthene, benzo[ a]pyrene, and benz[ a]anthracene undergo dynamic quenching, while for the remaining PAHs the dynamic and static processes coexist. In micellar CPB solutions the static quenching mechanism is predominant. The correlations existing between the quenching constant in the premicellar zone and topological and geometrical descriptors of the PAHs show the different behavior of alternant and nonalternant hydrocarbons.