Positional assignment of differentially substituted bisaminoacylated pdCpAs

The synthesis and NMR analysis of a 2'-O-alanyl, 3'-O-[1-(13)C]valyl-pdCpA derivative has permitted the definitive assignment of the positions of acylation of tandemly activated pdCpAs, and the bisaminoacylated transfer RNAs derived therefrom.     

On the Photophysicochemical Properties of Selected Fluoroquinolones: Solvatochromic and Fluorescence Spectroscopy Study

The photophysicochemical properties of selected fluoroquinolones in different solvents of various physical properties, including polarity and hydrogen bonding ability, were investigated using steady state fluorescence spectroscopy. The solvent-dependant fluorescence emission spectra of selected fluoroquinolones, namely ciprofloxacin (CIPR) and enrofloxacin (ENRO), were employed to gain insights concerning its photophysicochemical properties of interests. Interestingly, fluorescence spectra of the selected drugs exhibited structured emission spectra in nonpolar solvents such as hexane, whereas unstructured spectra were observed in more polar solvents such as alcohols and water. Also, a notable bathochromic shift in $ \lambda_{{\max }}^{{em}} $ was observed in fluorescence spectra of both drugs with increasing solvent polarity that resulted in biphasic behavior upon applying the Lippert-Mataga correlation that correspond to general and specific solvent effects. Applying the Lippert-Mataga correlation to the fluorescence spectra of CIPR and ENRO in various solvents was employed to estimate the dipole moment difference between the ground and excited states of them, $ \Delta \mu \left( {{\mu_e} - {\mu_g}} \right) $ , where obtained results revealed the values of 9.4 and 16.2 Debye for the LE and ICT states of ENRO, respectively, and 8.0 and 16.2 Debye for the LE and ICT states of CIPR, respectively. Multiple linear regression analysis (MLRA) based on Kamlet-Taft equating was applied against absorption frequency (ν_abs), emission frequency (ν_em), Stokes shift (?ν), and fluorescence quantum yield (Φ_f), where obtained results revealed excellent correlation (R: 0.916–0.966) that are consistent with other results considering the effect of solvent polarizability, hydrogen bonding ability, and viscosity on the photophysicochemical properties of the studied fluoroquinolones.     

An experimental investigation of change detection in uncertain chain-like systems

Promising ongoing research on “smart” sensing technologies is offering low-cost alternatives and new opportunities for large-scale SHM. Networks of sensors with wireless communication and computational capabilities can be used to increase the spatial resolution of data collection while providing a distributed computing framework for implementing structural health monitoring algorithms. Robust and practical SHM methodologies being able to rapidly and accurately detect and assess changes in the monitored system are required to be at the core of these “smart” structures. A data-driven non-parametric identification technique is used to implement a robust change detection methodology for uncertain MDOF chain-like systems that can be implemented in densely distributed smart-sensor networks. Experimental data from a test-bed structure tested at Los Alamos National Laboratory are used to evaluate the effectiveness and reliability of the proposed SHM methodology. The results of this study showed that the proposed approach was able, in a rigorous statistical framework, to confidently detect the presence of structural changes, accurately locate the structural section where the change occurred, and provide an accurate estimate of the actual level of “change”. Additionally, a full-order finite element model of the test structure, as well as the results from the experimental modal identification using the ERA algorithm were employed to validate the results obtained in this change-detection study.     

Hierarchical Schur complement preconditioner for the stochastic Galerkin finite element methods

Use of the stochastic Galerkin finite element methods leads to large systems of linear equations obtained by the discretization of tensor product solution spaces along their spatial and stochastic dimensions. These systems are typically solved iteratively by a Krylov subspace method. We propose a preconditioner, which takes an advantage of the recursive hierarchy in the structure of the global matrices. In particular, the matrices posses a recursive hierarchical two‐by‐two structure, with one of the submatrices block diagonal. Each of the diagonal blocks in this submatrix is closely related to the deterministic mean‐value problem, and the action of its inverse is in the implementation approximated by inner loops of Krylov iterations. Thus, our hierarchical Schur complement preconditioner combines, on each level in the approximation of the hierarchical structure of the global matrix, the idea of Schur complement with loops for a number of mutually independent inner Krylov iterations, and several matrix–vector multiplications for the off‐diagonal blocks. Neither the global matrix nor the matrix of the preconditioner need to be formed explicitly. The ingredients include only the number of stiffness matrices from the truncated Karhunen–Loève expansion and a good preconditioned for the mean‐value deterministic problem. We provide a condition number bound for a model elliptic problem, and the performance of the method is illustrated by numerical experiments. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthèse et caractérisation d'une série de bis-9,9′(thio-9-acridinyl)-α,ω-alcanes

Some new bis-acridine derivatives have been prepared under phase transfer catalysis conditions. These are α,ω-bis-(9-thioacridinyl)alkanes with or without heteroatoms such as N or O, included into the bridge. In the latter case, general procedure has to be slightly modified due to a side-reaction leading to thiobenzyl derivatives, which increases in the conditions proposed in the first place. The compounds so prepared were characterized by their melting points, ¹H and ¹³C nmr data. Preliminary results referring to activity against P-388 lymphocitic leukemia are presented.     

Electrodeposited Co<Subscript>1-x</Subscript>Mo<Subscript>x</Subscript>S thin films as highly efficient electrocatalysts for hydrogen evolution reaction in acid medium

Efficient and cost-effective electrocatalysts for hydrogen evolution reaction (HER) are significant for the advancement of effective water splitting reaction. Herein, we describe the growth of cobalt molybdenum sulfide (CoMoS) at different composites of tightly packed nanocrystals, prepared by one step process of simple electrodeposition method on fluorine-doped tin oxide (FTO) substrate as highly active and low-cost HER electrocatalyst. The prepared electrocatalysts were characterized via various analytical techniques. The HER activity was evaluated through electrochemical methods such as cyclic voltammetry technique and impedance analysis. Exhaustive electrochemical examinations show that the Co_0.95Mo_0.05S achieved higher cathodic current density value of 14.3 mA/cm² at η?=?250 mV with a lowest Tafel slope value towards HER. Furthermore, the active surface area of the as-deposited composite materials has been calculated by cyclic voltammetry analysis. Hence, the present work illustrates that the Co_0.95Mo_0.05S composite can serve as an encouraging cost-effective substitute to platinum-based electrocatalyst for HER.     

Selection of a histidine-containing inhibitor of gelatinases through deconvolution of combinatorial tetrapeptide libraries

Summary A fully automated peptide synthesizer was used to generate tetrapeptide sublibraries from 24 natural and nonnatural amino acids, from which new inhibitors of gelatinases (matrix metalloproteinases MMP-2 and MMP-9) were selected as potential anticancer drugs. MMP-2 and MMP-9 from mouse Balbc/3T3 fibroblasts conditioned media were assayed in their linear range response by zymography to quantify inhibition at each step of the tetrapeptide library deconvolution. The histidine--amino caproic acid-alanine-histidine (His-Ahx-Ala-His) sequence was found to yield optimal inhibition of both MMP-2 and MMP-9. Inhibition by selected tetrapeptides was also evaluated with two other techniques, a native type IV collagen degradation assay and a fluorogenic enzymatic assay, confirming the tetrapeptide potency. The His-Ahx-Ala-His tetrapeptide also inhibited purified human MMP-2 and MMP-9 and the corresponding enzymes present in conditioned media from human tumour cells. Finally, the length of the spacer between the two terminal histidines was found to be crucial to the inhibitory potential. This approach may thus be considered as a successful strategy to yield specific peptide or pseudopeptide inhibitors, although their potency remains moderate, since it was measured before any chemical optimization was undertaken.Abbreviations AA amino acid - Ahx -amino caproic acid - APMA 4-aminophenylmercuric acetate - DNP 2,4-dinitrophenyl - ECM extracellular matrix - MMP matrix metalloproteinase - Nma N-methylanthranilic acid - Nip para-nitrophenylalanine - TIMP tissue inhibitor of metalloproteinase - Z benzyloxycarbonyl     

Design and Synthesis of Novel Chiral Dirhodium(II) Carboxylate Complexes for Asymmetric Cyclopropanation Reactions

A novel approach to the design of dirhodium(II) tetracarboxylates derived from (S)‐amino acid ligands is reported. The approach is founded on tailoring the steric influences of the overall catalyst structure by reducing the local symmetry of the ligand's N‐heterocyclic tether. The application of the new approach has led to the uncovering of [Rh₂(S‐^tertPTTL)₄] as a new member of the dirhodium(II) family with extraordinary selectivity in cyclopropanation reactions. The stereoselectivity of [Rh₂(S‐^tertPTTL)₄] was found to be comparable to that of [Rh₂(S‐PTAD)₄] (up to >99 % ee), with the extra benefit of being more synthetically accessible. Correlations based on X‐ray structures to justify the observed enantioinduction are also discussed.     

Bis-Thioether-Containing Lipid Chains in Cationic Amphiphiles: Physicochemical Properties and Applications in Gene Delivery

Cationic amphiphiles featuring two thioether functions in each lipid chain of bicatenar cationic amphiphiles are reported here for the first time. The physicochemical properties and transfection abilities of these new amphiphiles were compared with those of already reported analogues featuring either (i) saturated, (ii) unsaturated or (iii) mono-thioether containing lipid chains. The homogeneity of the series of new compounds allowed to clearly underscore the effect of bis-thioether containing lipid chains. This study shows that besides previous strategies based on unsaturation or ramification, the incorporation of two thioether functions per lipid chain constitutes an original complementary alternative to tune the supramolecular properties of amphiphilic compounds. The potential of this strategy was evaluated in the context of gene delivery and report that two cationic amphiphiles (i. e. 4 a and 4 b) can be proposed as new efficient transfection reagents.     

Micro- and nano-thermal analysis applied to multi-layered biaxially-oriented polypropylene films

In this paper we compare Wollaston and silicon probes for localized thermal analysis measurements (LTA) on biaxially oriented polypropylene (BOPP) films. Up till now, no real comparison was reported in literature between the different transition temperatures measured using Wollaston and silicon probes. Using different types of probes for studying the same material proves to be very interesting. Using the Wollaston probe, the thermal properties and thickness of a 1 μm thick skin layer can be determined by through-thickness local thermal analysis measurements. The improved resolution of the silicon probes, enables the measurement of thermal properties of individual layers in a cross-sectioned film, even for layers of only 1 μm thickness. Based on the results, the silicon probes seem to be more sensitive toward the start of the melting process, since the silicon probe already penetrates at lower temperature, as compared to the Wollaston probes. This sensitivity can be exploited for studying the effect of variations in thermal history between or within samples.