Cyclochiral resorcin[4]arenes as effective enantioselectors in the gas phase

The effect of cyclochirality of rccc‐2,8,14,20‐tetra‐n‐decyl‐4,10,16,22‐tetra‐O‐methylresorcin[4]arene (C) on the enantiodiscrimination of a number of chiral bidentate and tridentate aromatic and aliphatic biomolecules (G) has been investigated by nano‐electrospray ionization (nano‐ESI)‐Fourier transform ion cyclotron resonance mass spectrometry. The experimental approach is based on the formation of diastereomeric proton‐bound [C·H·G]⁺ complexes by nano‐ESI of solutions containing an equimolar amount of quasi‐enantiomers (C) together with the chiral guest (G) and the subsequent measurement of the rate of the G substitution by the attack of several achiral and chiral amines. In general, the heterochiral complexes react faster than the homochiral ones, except when G is an aminoalcoholic neurotransmitter whose complexes, beyond that, exhibit the highest enantioselectivity. The kinetic results were further supported by both collision‐induced dissociation experiments on some of the relevant [C₂·H·G]⁺ three‐body species and Density functional theory (DFT) calculations performed on the most selective systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Sobolev Periodic Solutions of Nonlinear Wave Equations in Higher Spatial Dimensions

We prove the existence of Cantor families of periodic solutions for nonlinear wave equations in higher spatial dimensions with periodic boundary conditions. We study both forced and autonomous PDEs. In the latter case our theorems generalize previous results of Bourgain to more general nonlinearities of class C ^k and assuming weaker non-resonance conditions. Our solutions have Sobolev regularity both in time and space. The proofs are based on a differentiable Nash–Moser iteration scheme, where it is sufficient to get estimates of interpolation-type for the inverse linearized operators. Our approach works also in presence of very large “clusters of small divisors”.     

A closure approximation for nematic liquid crystals based on the canonical distribution subspace theory

 A closure approximation for nematic polymers is presented. It approximates the fourth rank order tensor in terms of lower rank tensors, and is derived in the framework of the canonical distribution subspace theory. This approach requires a choice of the class of distributions: Here the set of Bingham distributions is chosen, as already introduced by Chaubal and Leal (1998). The closure is written in a generic frame of reference, and in an explicit form, so that it can be easily implemented. Such formulation also permits studying the closure approximation with continuation tools, which rather completely describe the system dynamics. The predictions can then be compared with those obtained with the exact model. The shear flow is considered as a test, since this flow condition appears to be the most demanding for closure approximations for nematic polymers. Received: 30 November 1999/Accepted: 30 November 1999     

Optical Properties of M(II) Schiff-base Complexes Dispersed in Ethylene based Polymers

Summary: Several salicylaldiminate M(II) complexes of Nickel, Copper and Cobalt have been prepared and mixed with ethylene based polymers in order to prepare new composite materials with interesting morphological and optical properties by profiting of the presence of alkyl chains and push-pull substituents connected to the ligand structure. The phase dispersion behaviour of the binary films has been studied by scanning electron microscopy (SEM) and x-ray microanalysis, whereas the optical properties of the composite samples have been evaluated by UV-vis and fluorescence spectroscopy. The results in absorption have been analysed in terms of the anisotropy induced by the mechanical orientation of the polymer matrix and by the role of the metal centre according to the different strength of the complexes transition dipole moment. The luminescence behaviour have been discussed in terms of potential developments aimed at preparing polymeric supported Schiff base ligands for metal ions sensor applications.     

Ultrafast and selective labeling of endogenous proteins using affinity-based benzotriazole chemistry

Chemical modification of proteins is enormously useful for characterizing protein function in complex biological systems and for drug development. Selective labeling of native or endogenous proteins is challenging owing to the existence of distinct functional groups in proteins and in living systems. Chemistry for rapid and selective labeling of proteins remains in high demand. Here we have developed novel affinity labeling probes using benzotriazole (BTA) chemistry. We showed that affinity-based BTA probes selectively and covalently label a lysine residue in the vicinity of the ligand binding site of a target protein with a reaction half-time of 28 s. The reaction rate constant is comparable to the fastest biorthogonal chemistry. This approach was used to selectively label different cytosolic and membrane proteins in vitro and in live cells. BTA chemistry could be widely useful for labeling of native/endogenous proteins, target identification and development of covalent inhibitors.

Affinity-based benzotriazole (BTA) probes selectively and covalently label native proteins or endogenous proteins in cells with a fast reaction rate. It is enormously useful for characterizing protein function in biological systems and for drug development.     

Natural Formulations Based on Olea europaea L. Fruit Extract for the Topical Treatment of HSV-1 Infections

In the present study, a hydroxytyrosol-rich Olea europaea L. fruit extract (OFE) was added to three thoroughly green formulations—hydrogel, oleogel, and cream—in order to evaluate their antiviral activity against HSV-1. The extract was characterized by different analytical techniques, i.e., FT-IR, XPS, and TGA. HPLC analyses were carried out to monitor the content and release of hydroxytyrosol in the prepared formulations. The total polyphenol content and antioxidant activity were investigated through Folin–Ciocâlteu’s reagent, DPPH, and ABTS assays. The ability of the three formulations to convey active principles to the skin was evaluated using a Franz cell, showing that the number of permeated polyphenols in the hydrogel (272.1 ± 1.8 GAE/g) was significantly higher than those in the oleogel and cream (174 ± 10 and 179.6 ± 2 GAE/g, respectively), even if a negligible amount of hydroxytyrosol crossed the membrane for all the formulations. The cell viability assay indicated that the OFE and the three formulations were not toxic to cultured Vero cells. The antiviral activity tests highlighted that the OFE had a strong inhibitory effect against HSV-1 with a 50% inhibitory concentration (IC50) at 25 µg/mL, interfering directly with the viral particles. Among the three formulations, the hydrogel exhibited the highest antiviral activity also against the acyclovir-resistant strain.     

Gaussian Amplitude Amplification for Quantum Pathfinding

We study an oracle operation, along with its circuit design, which combined with the Grover diffusion operator boosts the probability of finding the minimum or maximum solutions on a weighted directed graph. We focus on the geometry of sequentially connected bipartite graphs, which naturally gives rise to solution spaces describable by Gaussian distributions. We then demonstrate how an oracle that encodes these distributions can be used to solve for the optimal path via amplitude amplification. And finally, we explore the degree to which this algorithm is capable of solving cases that are generated using randomized weights, as well as a theoretical application for solving the Traveling Salesman problem.     

Zinc Interactions with a Soluble Mutated Rat Amylin to Mimic Whole Human Amylin: An Experimental and Simulation Approach to Understand Stoichiometry,Speciation and Coordination of the Metal Complexes

Islet amyloid polypeptide (IAPP) is a hormone co-secreted with insulin and zinc from pancreatic β-cells. To overcome the low solubility of human IAPP, we characterized zinc complexes species formed with 1) a mutated form of rat-IAPP(1–37; R18 H) able to mimic the human IAPP, 2) the r-IAPP(1–37) and the IAPP(1–8) fragment. Stoichiometry, speciation and coordination features of zinc(II) complexes were unveiled by ESI-MS, potentiometry and NMR measurements combined with DFT and free-energy simulations. Mononuclear species start to form around pH 6; Zn²⁺ binds both His18 and N-amino terminus in rat-IAPP(1–37; R18 H). The in silico study allows us to assess not only a structured turn compact domain in r-IAPP(1–37) and r-IAPP(1–37; R18 H) featured by a different free energy barrier for the transition from the compact to elongated conformation upon the coordination of Zn²⁺, but also to bring into light a coordination shell further stabilized by noncovalent interactions.     

Antibacterial activity of a new class of tris homoleptic Ru (II)-complexes with alkyl-tetrazoles as diimine-type ligands

Herein, we describe a new family of tris chelate homoleptic Ru (II) complexes, [Ru(N^N) ₃ ] ²⁺ , where the role of the diimine-type ligands (N^N) was fulfilled by 2-pyridyl (PTZ) or 2-quinolyl tetrazole (QTZ) derivatives decorated with various alkyl substituents at the N-2 position of the tetrazole ring. The new Ru (II) complexes with general formula [Ru (PTZ-R) ₃ ] ²⁺ and [Ru (QTZ-R) ₃ ] ²⁺ , were obtained as mixtures of facial (fac) and meridional (mer) isomers, as suggested by NMR (¹H, ¹³C) experiments, and confirmed in the case of mer-[Ru (QTZ-Me) ₃ ] ²⁺ , by X-ray crystallography. The photophysical behavior of the tetrazole-based [Ru(N^N) ₃ ] ²⁺ type species was investigated by UV–vis absorption spectroscopy, providing trends typical of polypyridyl Ru (II) complexes. The new homoleptic complexes fac/mer- [Ru (PTZ-R) ₃ ] ²⁺ and fac/mer- [Ru (QTZ-R) ₃ ] ²⁺ have been assessed for any eventual antimicrobial activity towards two different bacteria such as Gram-negative Escherichia coli and Gram-positive Deinococcus radiodurans. Whereas being inactive toward E. coli, the response of agar disks diffusion tests suggested that some of the new fac/mer Ru (II) complexes could inhibit the growth of D. radiodurans. This effect was further investigated by determining the growth kinetics in liquid medium of D. radiodurans exposed to the fac/mer- [Ru (PTZ-R) ₃ ] ²⁺ and fac/mer- [Ru (QTZ-R) ₃ ] ²⁺ complexes at different concentrations. The outcome of these experiments highlighted that the turn-on of the growth inhibitory effect took place as the linear hexyl chain was appended to the PTZ or QTZ scaffold, suggesting also how the inhibitory activity appeared more pronouncedly exerted by the facial isomers fac- [Ru (PTZ-Hex) ₃ ] ²⁺ and fac- [Ru (QTZ-Hex) ₃ ] ²⁺ (MIC = ca. 3.0 μg/ml) with respect to the corresponding meridional isomers (MIC = ca. 6.0 μg/ml).