New nucleoside analogs from 2-amino-9-(beta-D-ribofuranosyl)purine

Four novel derivatives of 2-amino-9-(beta-D-ribofuranosyl)purine (1) were synthesised and fully characterised. When 1 was reacted with chloroacetaldehyde (a), 2-chloropropanal (b), bromomalonaldehyde (c) and a mixture of chloroacetaldehyde + malonaldehyde (d), 3-(beta-D-ribofuranosyl)-imidazo-[1,2a]purine (2), 3-(beta-D-ribofuranosyl)-5-methylimidazo-[1,2a]purine (3), 3-(beta-D-ribofuranosyl)-5-formylimidazo-[1,2a]purine (4) and 9-(beta-D-ribofuranosyl)-2-(3,5-diformyl-4-methyl-1,4-dihydro-1-pyridyl)purine (5) were formed, respectively. The products were isolated, purified by chromatography and characterised by MS, complete NMR assignment as well as fluorescence and UV spectroscopy. The yields of these reactions were moderate (14-20%). The fluorescence properties differed from those of the starting compound and the quantum yields were considerably lower.     

Precipitates originating from tungsten crucible parts in AlN bulk crystals grown by the PVT method

In order to evaluate the possible involvement of crucible materials in the growth of AlN bulk crystals grown by physical vapor transport, we applied growth conditions with a high vertical thermal gradient and hence high supersaturation of aluminum vapor. Under these conditions, precipitates formed causing diffuse grayish substructures at the initial growth interface and in the crystal body, decorating dislocations. Electron microscopy studies revealed that the precipitates are elongated, single‐phase particles with sizes of 50–500 nm of commensurate structure, oriented along the <110> direction. Chemical analysis of the precipitates showed tungsten as well as carbon and oxygen. The lattice parameters of the precipitates are in close agreement to hexagonal tungsten hemicarbide (W₂C). The possible transport from the tungsten parts and its conversion into tungsten hemicarbide precipitates is discussed. We thus conclude that the W₂C precipitates may contribute to the decoration of dislocations, even in growth with moderate thermal gradients.     

Normative KGP agents

We extend the logical model of agency known as the KGP model, to support agents with normative concepts, based on the roles an agent plays and the obligations and prohibitions that result from playing these roles. The proposed framework illustrates how the resulting normative concepts, including the roles, can evolve dynamically during the lifetime of the agent. Furthermore, we illustrate how these concepts can be combined with the existing capabilities of KGP agents in order to plan for their goals, react to changes in the environment, and interact with other agents. Our approach gives an executable specification of normative concepts that can be used directly for prototyping applications. Fariba Sadri is a senior lecturer at Imperial College London, from where she received her PhD. Her earlier work concentrated on integrity of deductive databases and temporal reasoning, in particular using the event calculus. In more recent years her work has been on agent technologies and multi-agent systems. She has worked on logic-based agent models, reasoning, dynamic belief revision, and inter-agent communication and negotiation for resources. She was co-awarded an EPSRC grant for research into logic-based multi-agents and was co-investigator in the EU SOCS project. Kostas Stathis is a senior lecturer at Royal Holloway, University of London and he holds a PhD from Imperial College London. His research interests are in the area of computational intelligence in general and in the intersection of computational logic and cognitive systems for social computing applications in particular. His research interests include: representation of human-computer (or computer-computer) interaction as a game; cognitive & autonomous agents; artificial agent societies; agent communication; programmable agents and agent platforms. He is a co-investigator of the EU ArguGRID project and was a co-investigator of the EU SOCS project. Francesca Toni is a senior lecturer at Imperial College London, from where she received her PhD. Her earlier work focused on abductive reasoning. In more recent years, she focused on argumentation, agent models and multi-agent systems. She has worked on computational logic-based agent models, agent reasoning, dynamic belief revision, and inter-agent communication and negotiation for resources. She has been co-ordinator of the EU SOCS project, which developed the KGP model of agency, and is coordinator of the EU ArguGRID project, on the application of argumentative agents within grid systems.     

Adding a Structural Context to the Deprotometalation and Trans‐Metal Trapping Chemistry of Phenyl‐Substituted Benzotriazole

Organometallic bases are becoming increasingly complex, because mixing components can lead to bases superior to single‐component bases. To better understand this superiority, it is useful to study metalated intermediate structures prior to quenching. This study is on 1‐phenyl‐1H‐benzotriazole, which was previously deprotonated by an in situ ZnCl₂ ? TMEDA/LiTMP (TMEDA=N,N,N′,N′‐tetramethylethylenediamine; TMP=2,2,6,6‐tetramethylpiperidide) mixture and then iodinated. Herein, reaction with LiTMP exposes the deficiency of the single‐component base as the crystalline product obtained was [{4‐R‐1‐(2‐lithiophenyl)‐1H‐benzotriazole ? 3THF}₂], [R=2‐C₆H₄(Ph)NLi], in which ring opening of benzotriazole and N₂ extrusion had occurred. Supporting lithiation by adding iBu₂Al(TMP) induces trans‐metal trapping, in which C?Li bonds transform into C?Al bonds to stabilise the metalated intermediate. X‐ray diffraction studies revealed homodimeric [(4‐R′‐1‐phenyl‐1H‐benzotriazole)₂], [R′=(iBu)₂Al(μ‐TMP)Li], and its heterodimeric isomer [(4‐R′‐1‐phenyl‐1H‐benzotriazole){2‐R′‐1‐phenyl‐1H‐benzotriazole}], whose structure and slow conformational dynamics were probed by solution NMR spectroscopy.     

A Statewide Implementation of the Critical Features of Professional Development: Impact on Teacher Outcomes

This study is focused on a statewide implementation of the core conceptual framework for effective professional development in the United States. and associated impact on teacher quality and attitudes. The framework included content focus, active learning, coherence, duration, and collective participation. There were 252 participants in the study, who were involved in one of the five science or six mathematics programs. Findings indicated a significant impact on teacher quality for all participating programs. Teacher attitudes were positive at the baseline, and remained positive with some improvement at the end of the program. However, teacher perceived preparedness increased significantly across the duration of the program. Discussion of the findings and implications for professional development programs internationally are shared.     

Mass spectrometric characterization of peptides containing different oxidized tryptophan residues

The term reactive oxygen species refers to small molecules that can oxidize, for example, nearby proteins, especially cysteine, methionine, tryptophan, and tyrosine residues. Tryptophan oxidation is always irreversible in the cell and can yield several oxidation products, such as 5-hydroxy-tryptophan (5-HTP), oxindolylalanine (Oia), kynurenine (Kyn), and N-formyl-kynurenine (NFK). Because of the severe effects that oxidized tryptophan residues can have on proteins, there is a great need to develop generally applicable and highly sensitive techniques to identify the oxidized residue and the oxidation product. Here, the fragmentation behavior of synthetic peptides corresponding to sequences recently identified in three skeletal muscle proteins as containing oxidized tryptophan residues were studied using postsource decay and collision-induced dissociation (CID) in matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF)/TOF mass spectrometry (MS) and CID in an electrospray ionization (ESI) double quadrupole TOF-MS. For each sequence, a panel of five different peptides containing Trp, 5-HTP, Kyn, NFK, or Oia residue was studied. It was always possible to identify the modified positions by the y-series and also to distinguish the different oxidation products by characteristic fragment ions in the lower mass range by tandem MS. NFK- and Kyn-containing peptides displayed an intense signal at m/z 174.1, which could be useful in identifying accordingly modified peptides by a sensitive precursor ion scan. Most importantly, it was always possible to distinguish isomeric 5-HTP and Oia residues. In ESI- and MALDI-MS/MS, this was achieved by the signal intensity ratios of two signals obtained at m/z 130.1 and 146.1. In addition, high collision energy CID in the MALDI-TOF/TOF-MS also permitted the identification of these two isomeric residues by their v- and w-ions, respectively.     

Biomimetic total synthesis of angelicoin A and B via a palladium-catalyzed decarboxylative prenylation-aromatization sequence

Five-step total syntheses of angelicoin A and B from 2,2,6-trimethyl-4-dioxinone are reported using late stage biomimetic aromatization reactions via diketo-dioxinones as intermediates. In addition, with angelicoin A, this aromatization was coupled with a palladium-catalyzed decarboxylative prenylation in a one-pot sequence as the key step.