Fluorescence spectroscopy has been used to characterize the structure of a unique class of anionic macromolecules: starburst dendrimers (SBDs) possessing an external anionic surface. Pyrene was used as a photoluminescence probe to sense various hydrophobic sites in the microheterogeneous architecture offered by poly(amidoamine) starburst dendrimers possessing sodium carboxylated surfaces. A series of 10 different "half-generations, n.5" starburst dendrimers, which differ systematically in molecular weight, size, and surface charge density, have been studied. The probe method provides experimental evidence for a structural surface transition between generations 3.5 and 4.5. The same probe method was applied to study how the structural properties of the starburst dendrimers determine their interactions with small ionic amphiphilic molecules. Whereas starburst dendrimers do not noticeably affect the micellization process of an anionic surfactant (sodium dodecyl sulfate, SDS), the association process with a cationic surfactant (dodecyltetrammonium bromide, DTAB) leads to the formation of two different types of SBD-templated surfactant aggregates. Addition of DTAB to aqueous solutions containing the earlier generation (0.5-3.5) SBD leads to the formation of SBD-templated surfactant aggregates that result from noncooperative, random condensation of surfactant molecules on the anionic dendrimer surface. Addition of DTAB to aqueous solutions containing later generation (4.5-9.5) SBDs leads to the formation of SBD-templated surfactant aggregates resulting from initial, noncooperative, random condensation, followed by cooperative condensation of surfactant molecules on the anionic dendrimer surface. The results are shown to be consistent with a change in the morphology of SBDs from an open, branched structure for generations 0.5-3.5 to a closed, increasingly compact surface for generations 4.5-9.5.the early generations were found to possess average structures that were very open, whereas the later generations were more closed,

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We report the development of a new type of hydrogel in which a cosolvent has been added to the water component. The gel networks are based on the well-known poly(vinyl alcohol)-borate systems (PVA-borate). However, it is shown that the rheological and solubilizing properties of the hydrogels can be modified drastically by the addition of a cosolvent. The studies have focused on 1-propanol as the added liquid, although it is shown that others (propylene carbonate, 1-pentanol, cyclohexanone, and 2-butanol) are amenable to making modified hydrogels as well. In addition to the rheological measurements, the gels have been investigated by differential scanning calorimetry (free water index) and determination of their solubilizing power. Finally, the gels have been applied to clean and oxidized varnish (patina) from the surface of a XVI-XVII century oil-on-wood painting by Ludovico Cardi detto il Cigoli. The mode of cleaning by and removal of the PVA-borate water/1-propanol gel from the painted surface demonstrate several advantages over other gels used in art conservation.

Trodusquemine is an aminosterol known to prevent the binding of misfolded protein oligomers to cell membranes and to reduce their toxicity in a wide range of neurodegenerative diseases. Its precise...

We introduce an effective technique for the calculation of the binding free energy in drug-receptor systems using nonequilibrium molecular dynamics and application of the Jarzynski theorem. In essence, this novel methodology constitutes the nonequilibrium adaptation of an ancient free energy perturbation technique called Double Annihilation Method, invented more than 25 years ago [J. Chem. Phys. 1988, 89, 3742-3746] and upon which modern approaches of binding free energy computation in drug-receptor systems are heavily based. The proposed computational approach, termed Fast Switching Double Annihilation Methods (FS-DAM) in honor of its ancient ancestor, is applied to a prototypical example system with multiple binding sites, proving its computational potential and versatility in unraveling multiple site or allosteric binding processes.