Through-space delocalized water-soluble paracyclophane bichromophores: new fluorescent optical reporters

Conjugated polymers and oligomers can serve as highly responsive fluorescent reporters for biosensor applications. However, their optical properties in aqueous media are highly dependent upon environmental conditions. The structure of the paracyclophane framework provides a platform for designing optical reporters that show little sensitivity to surfactants, and thus is well-suited for fluorescent assays. The permanent intramolecular delocalization through the paracyclophane core dominates intermolecular perturbations in spontaneously formed aggregates.     

Water-soluble oligomer dimers based on paracyclophane: a new optical platform for fluorescent sensor applications

Water soluble paracyclophane chromophore dimers provide optical reporters that show little sensitivity to surfactants and thus are ideal for biosensor design. Strong intramolecular delocalization circumvents complications from intermolecular delocalization in spontaneously formed aggregates. The synthesis of 2 involves a novel TBAT deprotection/butane sultone ring-opening sequence, which should be general for the preparation of water-soluble conjugated oligomers and polymers.     

Nucleocyclitols. Synthesis of substituted purinyl-muco-inositol derivatives

Several carbocyclic nucleoside analogs possessing a 6-substituted purine linked to a mesylated muco-inositol were synthesized. The coupling of triethylamine-activated 6-chloropurine with 2,3-anhydro-l,5,6-tri-O-(methanesulfonyl)-epi-inositol gave a 6-chloro purinyl muco-inositol amenable to further synthetic transformations in the heterocyclic moiety by substitution of the chlorine atom by nitrogen nucleophiles such as methylamino, diethylamino, benzylamino, hydrazino, morpholino, hydroxylamino, piperidino, and glycyl groups.     

Oxonitrogenated Derivatives of Eremophilans and Eudesmans: Antiproliferative and Anti-Trypanosoma cruzi Activity

Cancer is one of the most important causes of death worldwide. Solid tumors represent the vast majority of cancers (>90%), and the chemotherapeutic agents used for their treatment are still characterized by variable efficacy and toxicity. Sesquiterpenes are a group of natural compounds that have shown a wide range of biological activities, including cytotoxic and antiparasitic activity, among others. The antiproliferative activity of natural sesquiterpenes, tessaric acid, ilicic acid, and ilicic alcohol and their semisynthetic derivatives against HeLa, T-47D, WiDr, A549, HBL-100, and SW1573 cell lines were evaluated. The effect of the compounds on Trypanosoma cruzi epimastigotes was also assessed. The selectivity index was calculated using murine splenocytes. Derivatives 13 and 15 were the most antiproliferative compounds, with GI₅₀ values ranging between 5.3 (±0.32) and 14 (±0.90) μM, in all cell lines tested. The presence of 1,2,3-triazole groups in derivatives 15–19 led to improvements in activity compared to those corresponding to the starting natural product (3), with GI₅₀ values ranging between 12 (±1.5) and 17 (±1.1) μM and 16 being the most active compound. In relation to the anti-T. cruzi activity, derivatives 7 and 16 obtained from tessaric acid and ilicic acid were among the most active and selective compounds with IC₅₀ values of 9.3 and 8.8 µM (SI = 8.0 and 9.4), respectively.     

Multivariate optimization of the Kharasch–Sosnovsky allylic oxidation of olefins

The multivariate optimization method known as simplex is applied to the Kharasch–Sosnovsky allylic oxidation of double bonds. By applying this method, the amounts of three variables (copper source, oxidant, and additive) are optimized at the same time. Under the conditions thus obtained the reaction takes place in a considerable shorter time, being the alkene the limiting reagent. These conditions are applied to some monoterpenes and sesquiterpenes leading regioselectively to the corresponding benzoate esters, opening a route to the employment of this reaction in the synthesis of more complex molecules.     

The movement of a forager: strategies for the efficient use ofresources

We study a simple model of a foraging animal that modifies the substrate on which itmoves. This substrate provides its only resource, and the forager manages it by taking alimited portion at each visited site. The resource recovers its value after the visitfollowing a relaxation law. We study different scenarios to analyze the efficiency of themanaging strategy, corresponding to control the bite size. We observe the non trivialemergence of a home range, that is visited in a periodic way. The duration of thecorresponding cycles and the transient until it emerges is affected by the bite size. Ourresults show that the most efficient use of the resource, measured as the balance betweengathering and traveled distance, corresponds to foragers that take larger portions butwithout exhausting the resource. We also analyze the use of space determining the numberof attractors of the dynamics, and we observe that it depends on the bite size and therecovery time of the resource.     

On feedback and stable price adjustment mechanisms

Given an excess demand function of an economy, say Z(p)$Z(p)$, a stable price adjustment mechanism (SPAM) guarantees convergence of solution path p(t,_p0)$p(t,p_0)$ to an equilibrium _peq$p_{\mathit{eq}}$ solution of Z(p)=0$Z(p)=0$. Besides, all equilibrium points of Z(p)$Z(p)$ are asymptotically stable. Some SPAMs have been proposed, including Newton and transpose Jacobian methods. Despite this powerful stability property of SPAMs, their acceptation in the economics community has been limited by a lack of interpretation. This paper focuses on this issue. Specifically, feedback control theory is used to link SPAMs and price dynamics models with control inputs, which match the economically intuitive Walrasian Hypothesis (i.e., prices change with excess demand sign). Under mild conditions, it is shown the existence of a feedback function that transforms the price dynamics into a desired SPAM. Hence, a SPAM is interpreted as a fundamental (e.g., Walrasian) price dynamics under the action of a feedback function aimed to stabilize the equilibrium set of the excess demand function.     

Linear and nonlinear optical properties of carbon nanotube-coated single-mode optical fiber gratings

Single-wall carbon nanotube deposition on the cladding of optical fibers has been carried out to fabricate an all-fiber nonlinear device. Two different nanotube deposition techniques were studied. The first consisted of repeatedly immersing the optical fiber into a nanotube supension, increasing the thickness of the coating in each step. The second deposition involved wrapping a thin film of nanotubes around the optical fiber. For both cases, interaction of transmitted light through the fiber core with the external coating was assisted by the cladding mode resonances of a tilted fiber Bragg grating. Ultrafast nonlinear effects of the nanotube-coated fiber were measured by means of a pump-probe pulses experiment.     

Surface‐enhanced Raman scattering and density functional theory studies of bis(4‐aminophenyl)sulfone

Raman and surface‐enhanced Raman scattering (SERS) spectra of dapsone by using colloidal silver nanoparticles have been recorded. Density functional theory was used for the optimization of ground state geometries and simulation of the vibrational spectrum of this molecule. The SERS spectrum with a large silver cluster as a model metallic surface was simulated for the first time. Taking into account the experimental and calculated Raman as well as the SERS normal modes and the corresponding assignments, along with the modeling of the free dapsone and the one in the presence of the colloidal silver nanoparticles, the importance of the sulfone group on the SERS effect in dapsone was inferred. Copyright © 2009 John Wiley & Sons, Ltd.