synopsisNew experimental data were obtained by means of circular dichroism, melting, renaturation, and kinetic experiments, upon Cu2+ binding to DNA, poly dAT, and poly dGdC. They enable us to propose a model of binding giving a satisfactory explanation to all of the data found in the literature. Two types of binding sites are proposed: (a) a "sandwich" of C U~+ between two adjacent G-C pairs giving a charge-transfer complex, and (b) a chelate between a phosphate group and a nitrogen atom of the bases (N7 of guanine and N3 of cytosine at room temperature, N3 of adenine after thermal opening of A-T pair). Type (a) stabilizes the helix and keeps the two strands linked. Type (b) destabilizes the helii and explains why the kinetic rate of renaturation is the same as that of copper release.

This experimental paper deals with phase separations of binary mixtures composed of a continuous liquid crystal phase and an isotropic dispersed phase. In contrast to isotropic binary mixtures, the investigated mixtures do not lead to a full phase separation but to a self-ordering of colloidal particles, as reported earlier (Loudet, J. C. et al. Nature 2000, 407, 611). We present here further aspects of such phase separations which include the kinetics of the phase separation, the origin of the formation of dislocation-like patterns, the influence of surfactants, chiral additives, and temperature on the formed colloidal structures. The present results show that (i) the dislocations in chain arrays can be seen as kinetically frozen defects, (ii) temperature can be used to control the size of the domains formed upon demixing, (iii) a slight change in surface chemistry, via the addition of surfactants, profoundly alters the formed colloidal structures, and (iv) chiral additives allow the formation of unique helical pearl chains which reflect the symmetry of the liquid crystal phase they are embedded in.

Abstract— The molecule (1,1'‐dipyrenyl)‐methyl ether [dipyme] shows intramolecular excimer fluorescence in competition with fluorescence from the locally excited pyrene chromophore. This intensity ratio Ic/Im is sensitive to solvent viscosity. The molecule is soluble in synthetic phospholipid membranes. 1H NMR studies suggest that the molecule is localized in the hydrocarbon region of the membrane. Fluorescence measurements at various temperatures of dipyme dissolved in these membranes show that Ic/Im is exceedingly sensitive to fluidity changes accompanying both the pretransitions and the gel to liquid crystalline transitions of the membrane. These studies can be carried out at a mole ratio of probe to lipid 102‐103 smaller than that necessary to observe bimolecular pyrene excimer formation.

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