The Synthesis of Vicinal Diacylamines via Bamberger Ring Cleavage of Substituted Imidazoles. 1,2,4-Triacylaminobutanes Bearing Different Acyl Groups

Bamberger ring cleavage acylation of N-p-toluenesulfonyl (tosyl) histamine followed by hydrogenation yields 3,4-diacylaminobutanetosylamine, a triamine containing groups with different chemical reactivities.     

Sintering of Colloidal Ru/γ-Al2O3 Catalyst in Hydrogen

Colloidal 5.1 wt% Ru/γ-Al₂O₃ catalyst was prepared by a microwave assisted, solvothermal reduction of RuCl₃ in ethylene glycol in the presence of γ-Al₂O₃. The catalyst subjected to heat-treatment in hydrogen up to 700 °C, was characterized by BET, XRD, TEM and H₂ chemisorption. As-prepared catalyst contained Ru nanoparticles with mean size of 1.5 nm and narrow size distribution uniformly distributed over the support. The nanoparticles were stable on the alumina to 500 °C, but treatment at 600–700 °C caused some sintering of Ru due to migration and coalescence of a part of smallest ruthenium nanoparticles. However, even after H₂ treatment at 700 °C, large amount of Ru nanoparticles with sizes of 1–3 nm remained in the catalyst. H₂ chemisorption data revealed decrease of Ru dispersion from 0.28 to 0.19 by hydrogen treatment at 700 °C and were in good correspondence with TEM results. On the contrary, mean crystallite sizes obtained from XRD were strongly overestimated.     

Closed channel fabrication using micromolding of metallic glass

Casting and molding are attractive options for low cost mass production. Metallic glasses may avoid many of the problems associated with micromolding of metals such as high temperatures and pressures, costly mold production, and shrinkage due to crystallization. In this study, we have produced 100 μm², enclosed channels in metallic glass using a novel multilayer Si stack micromolding process. Scanning electron microscope (SEM) images of the enclosed channels are provided to verify that the closed channels extended through the sample.     

New Strategy for Optimizing Water Application under Trickle Irrigation

The determination of water application parameters for creating an optimal soil moisture profile represents a complex nonlinear optimization problem which renders traditional optimization into a cumbersome procedure. For this reason, an alternative methodology is proposed which combines a numerical subsurface flow model and artificial neural networks (ANN) for solving the problem in two, fully separate steps. The first step employs the flow model for calculating a large number of wetting profiles (output), obtained from a systematic variation of both water application and initial soil moisture (input). The resulting matrix of corresponding input/output values is used for training the ANN. The second step, the application of the fully trained ANN, then provides the irrigation parameters which range from a specified initial soil moisture to a desired crop-specific soil moisture profile. In order to avoid substantial disadvantages associated with the common feedforward backpropagation approach, a self-organizing topological feature map is implemented to perform this task. After a comprehensive sensitivity analysis, the new methodology is applied to the outcome of an irrigation experiment. The convincing results recommend the new methodology as a positive contribution towards an improved irrigation efficiency.     

Variation in the serotonin transporter gene modulates selective attention to threat.

The 5-HTTLPR is an insertion/deletion polymorphism in the promoter region of the serotonin transporter gene. Prior research has revealed associations between the short-allele variant of this polymorphism, enhanced self-reported negative emotionality, and hypersensitivity of fear relevant neural circuits. In a sample of 50 healthy women we examined the role of 5-HTTLPR for cognitive-affective processing of phylogenetical fear-relevant stimuli (spiders) in a dot probe task. In contrast to homozygote long-allele carriers (ll), participants carrying at least 1 short allele (ss and sl) selectively shifted attention toward pictures of spiders, when these were presented for a duration of 2,000 ms. These results argue for an involvement of 5-HTTLPR in cognitive processing of threatening stimuli and thus, underpin its general role for individual differences in negative affect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Active Site Mapping of Human Cathepsin F with Dipeptide Nitrile Inhibitors

Cleavage of the invariant chain is the key event in the trafficking pathway of major histocompatibility complex class II. Cathepsin S is the major processing enzyme of the invariant chain, but cathepsin F acts in macrophages as its functional synergist which is as potent as cathepsin S in invariant chain cleavage. Dedicated low‐molecular‐weight inhibitors for cathepsin F have not yet been developed. An active site mapping with 52 dipeptide nitriles, reacting as covalent–reversible inhibitors, was performed to draw structure–activity relationships for the non‐primed binding region of human cathepsin F. In a stepwise process, new compounds with optimized fragment combinations were designed and synthesized. These dipeptide nitriles were evaluated on human cysteine cathepsins F, B, L, K and S. Compounds 10 (N‐(4‐phenylbenzoyl)‐leucylglycine nitrile) and 12 (N‐(4‐phenylbenzoyl)leucylmethionine nitrile) were found to be potent inhibitors of human cathepsin F, with K_i values <10 nM . With all dipeptide nitriles from our study, a 3D activity landscape was generated to visualize structure–activity relationships for this series of cathepsin F inhibitors.     

Examination of a Structural Model of Peptidomimicry by Cyclic Acyldepsipeptide Antibiotics in Their Interaction with the ClpP Peptidase

The cyclic acyldepsipeptide (ADEP) antibiotics act by binding the ClpP peptidase and dysregulating its activity. Their exocyclic N‐acylphenylalanine is thought to structurally mimic the ClpP‐binding, (I/L)GF tripeptide loop of the peptidase's accessory ATPases. We found that ADEP analogues with exocyclic N‐acyl tripeptides or dipeptides resembling the (I/L)GF motif were weak ClpP activators and had no bioactivity. In contrast, ADEP analogues possessing difluorophenylalanine N‐capped with methyl‐branched acyl groups—like the side chains of residues in the (I/L)GF motifs—were superior to the parent ADEP with respect to both ClpP activation and bioactivity. We contend that the ADEP's N‐acylphenylalanine moiety is not simply a stand‐in for the ATPases' (I/L)GF motif; it likely has physicochemical properties that are better suited for ClpP binding. Further, our finding that the methyl‐branching on the acyl group of the ADEPs improves activity opens new avenues for optimization.     

Novel N‐ethyl‐2‐styrylquinolinium iodides as sensitizers in the photoinitiated free‐radical polymerization of trimethylolopropane triacrylate. II

Results of kinetic studies of two‐component photoinitiator systems used in the visible‐light photoinduced polymerization of 2‐ethyl‐2‐(hydroxymethyl)‐1,3‐propanediol triacrylate are presented. Nine different styrylquinolinum dyes coupled with n‐butyltriphenylborate as a coinitiator have been used as photoinitiating systems. Reactive radicals that initiate the polymerization are formed by the well‐known mechanism of photoinduced electron transfer between dye cations acting as electron acceptors and borate anions acting as electron donors. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010