Charge transfer efficiency in hybrid bulk heterojunction composites

On the basis of recently published electrochemical measurements, the charge transfer efficiency within CdSe nanocrystal/conducting polymer heterojunction composites was investigated by means of luminescence interaction strength. It was found that poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] and poly-9-vinylcarbazole luminescence was not totally quenched by nanocrystals, whereas poly-3-octylthiophene and polyvinylpyrrolidone was completely quenched. In case of poly-3-hexylthiophene, the nanocrystal luminescence was quenched. The results are in complete agreement with the electrochemical findings and thus, the CdSe nanocrystal/Polyvinylpyrrolidone composite should be a promising material for electroluminescent devices.     

Esmodil: an acetylcholine mimetic resurfaces in a Southern Australian marine sponge Raspailia (Raspailia) sp

Bioassay directed fractionation of a Raspailia (Raspailia) sp. (Order Poecilosclerida; Family Raspailiidae) collected during scientific trawling operations off the Northern Rottnest Shelf yielded as nematocidal agents the known metabolites, phorboxazoles A (1) and B (2). Further examination revealed the new natural product but known synthetic compound, esmodil (3). The structure for 3 was confirmed by spectroscopic analysis and total synthesis.     

Screening, library-assisted identification and validated quantification of 23 benzodiazepines, flumazenil, zaleplone, zolpidem and zopiclone in plasma by liquid chromatography/mass spectrometry with atmospheric pressure chemical ionization

A liquid chromatographic/mass spectrometric assay with atmospheric pressure chemical ionization (LC/APCI-MS) is presented for fast and reliable screening and identification and also for precise and sensitive quantification in plasma of the 23 benzodiazepines alprazolam, bromazepam, brotizolam, camazepam, chlordiazepoxide, clobazam, clonazepam, diazepam, flunitrazepam, flurazepam, desalkylflurazepam, lorazepam, lormetazepam, medazepam, metaclazepam, midazolam, nitrazepam, nordazepam, oxazepam, prazepam, temazepam and tetrazepam, triazolam, their antagonist flumazenil and the benzodiazepine BZ1 (omega 1) receptor agonists zaleplone, zolpidem and zopiclone. It allows confirmation of the diagnosis of an overdose situation and monitoring of psychiatric patients' compliance. The analytes were isolated from plasma using liquid-liquid extraction and were separated on a Merck LiChroCART column with Superspher 60 RP Select B as the stationary phase. Gradient elution was performed using aqueous ammonium formate and acetonitrile. After screening and identification in the scan mode using the authors' LC/MS library, the analytes were quantified in the selected-ion monitoring mode. The quantification assay was fully validated. It was found to be selective proved to be linear from sub-therapeutic to over therapeutic concentrations for all analytes, except bromazepam. The corresponding reference levels the assay's accuracy and precision data for all studied substances are listed. The accuracy and precision data were within the required limits with the exception of those for bromazepam. The analytes were stable in frozen plasma for at least 1 month. The validated assay was successfully applied to several authentic plasma samples from patients treated or intoxicated with various benzodiazepines or with zaleplone, zolpidem or zopiclone. It has proven to be appropriate for the isolation, separation, screening, identification and quantification of the drugs mentioned above in plasma for clinical toxicology, e.g. in cases of poisoning, and forensic toxicology, e.g. in cases of driving under the influence of drugs.     

Discriminating the helical forms of peptides by NMR and molecular dynamics simulation

The HNCO NMR pulse sequence was applied to three selectively labeled (15)N and (13)C isotopic homologues of the peptide Ac-WAAAH(AAARA)(3)A-NH(2) to probe directly for hydrogen bonds between residues 8 and 11 (characteristic of a 3(10)-helix), 8 and 12 (alpha-helix), and 8 and 13 (pi-helix). The experiments demonstrate conclusively, and in agreement with circular dichroism studies, that the center of the peptide is alpha-helical; there is no discernible 3(10)- or pi-helix at these specific positions. Molecular dynamics simulations of the preceding peptide and Ac-(AAAAK)(3)A-NH(2) in water using the potential energy parameter set CHARMM22/CMAP correctly yield an alpha-helix, in contrast to simulations with the set CHARMM22, which result in a pi-helix.     

Synthesis and biological evaluation of new inhibitors of UDP-Galf transferase--a key enzyme in M. tuberculosis cell wall biosynthesis

Two iminosugars have been designed and synthesized as potential inhibitors of UDP-Galf transferase, an enzyme involved in Mycobacterium tuberculosis cell wall biosynthesis. The design is based on a proposed model of the transition state for the transferase reaction. One of the two racemic compounds is the first reported inhibitor of the target enzyme from M. smegmatis.     

Coordination chemistry of 2-(8-aminoquinolino)-4,6-di-tert-butylphenol with manganese(IV), iron(III), and cobalt(II/III):N,O-coordinated o-iminobenzosemiquinonate(1-) pi radical monoanions vs.o-iminophenolate(2-) dianions

The potentially tridentate ligand 2-(8-aminoquinolino)-4,6-di-tert-butylphenol, H[1LAP], has been synthesized and its coordination chemistry with Mn(IV), Fe(III), and Co(III) has been investigated by X-ray crystallography, electro- and magnetochemistry, electronic, Mossbauer and EPR spectroscopies. The following complexes have been prepared [MnIV(1LAP-H)2](1), St=3/2; [MnIV(1LAP-H)(1LISQ)](PF6).CH2Cl2 (2), St= 1; [FeIII(1LISQ)2](ClO4).0.5H2O (3), St=1/2; [FeIII(1LISQ)(3,5-dtcat)]2 (4), St= 0; K[CoII(1LISQ)(1LIBQ)](NCS)2 (5), St= 1; [CoIII2(NCS)2(1LAP-H)2(AQ)] (6), St=0, where (1LAP-H)2- corresponds to the o-iminophenolate(2-) dianion, (1LISQ)- is the o-iminobenzosemiquinonate(1-) pi radical derivative of the ligand H[1LAP], (1LIBQ)0 is the neutral iminobenzoquinone ligand, and 3,5-dtcat is 3,5-di-tert-butylcatecholate(2-) and N,N-coordinated (AQ) is 8-aminoquinoline. It is shown that the pi radical anions in 2, 3, 4 couple antiferromagnetically to the respective paramagnetic metal ion. Complex 4 is a dinuclear neutral complex with weak antiferromagnetic coupling between two [FeIII1LISQ)(3,5-dtcat)] halves. The asymmetrically ligated complex 6 contains two bridging (1LAP-H)2- ligands and two diamagnetic CoIII ions. In contrast, 5 is correctly described as [CoII(1LISQ)(1LIBQ)]+ rather than [CoIII(1LISQ)2]+ since it possesses a temperature-independent magnetic moment of mueff(10-298 K)= 3.0 muB indicating an St=1 ground state which is attained via strong antiferromagnetic coupling (|J> or =200 cm(-1)) between a high spin cobalt(II) ion (SCo=3/2) and a single pi radical anion (Srad=1/2).     

A new continuous flow isotope ratio mass spectrometry system for the analysis of delta2H, delta17O and delta18O of small (120 microg) water samples in atmospheric applications

A new continuous-flow system for the analysis of the complete stable isotopic composition of water vapor has been developed. The sample size is reduced to only 120 microg (identical with 120 nL of liquid substance) of water, yielding precisions of about 0.7, 1.3 and 7 per thousand for delta17O, delta18O and delta2H, respectively. The total time for the analysis of a sample is about 150 min including purging times. Oxidized steel surfaces can be a source of memory effects which can be corrected for. The system is predestined for atmospheric applications in the tropopause region, as the sample can be directly introduced into the system from a cryogenic trap.     

Rapid prototyping of polymer microsystems via excimer laser ablation of polymeric moulds

This study presents a novel method for rapid prototyping of polymer microsystems. The method is based on excimer laser ablation of a thermally and mechanically stable polymer, such as PEEK (poly-ether-ether-ketone). A negative of the desired microsystem is laser machined in PEEK, which can then be used directly for hot embossing or injection moulding of a series of prototypes. This approach is very rapid and considerably cheaper than more traditional approaches to toolmaking, while still performing well in terms of reproduction of tool dimensions. The reduction in time and cost for a master tool using this method opens up new possibilities for testing small series in the R&D phase of a microsystem. Finally, two particular applications of the technique are presented.     

Army ants algorithm for rare event sampling of delocalized nonadiabatic transitions by trajectory surface hopping and the estimation of sampling errors by the bootstrap method

The most widely used algorithm for Monte Carlo sampling of electronic transitions in trajectory surface hopping (TSH) calculations is the so-called anteater algorithm, which is inefficient for sampling low-probability nonadiabatic events. We present a new sampling scheme (called the army ants algorithm) for carrying out TSH calculations that is applicable to systems with any strength of coupling. The army ants algorithm is a form of rare event sampling whose efficiency is controlled by an input parameter. By choosing a suitable value of the input parameter the army ants algorithm can be reduced to the anteater algorithm (which is efficient for strongly coupled cases), and by optimizing the parameter the army ants algorithm may be efficiently applied to systems with low-probability events. To demonstrate the efficiency of the army ants algorithm, we performed atom-diatom scattering calculations on a model system involving weakly coupled electronic states. Fully converged quantum mechanical calculations were performed, and the probabilities for nonadiabatic reaction and nonreactive deexcitation (quenching) were found to be on the order of 10(-8). For such low-probability events the anteater sampling scheme requires a large number of trajectories ( approximately 10(10)) to obtain good statistics and converged semiclassical results. In contrast by using the new army ants algorithm converged results were obtained by running 10(5) trajectories. Furthermore, the results were found to be in excellent agreement with the quantum mechanical results. Sampling errors were estimated using the bootstrap method, which is validated for use with the army ants algorithm.     

Photoinduced Ru-Yb energy transfer and sensitised near-IR luminescence in a coordination polymer containing co-crystallised [Ru(bipy)(CN)4]2- and Yb(III) units

Co-crystallisation of the anionic cyanometallate chromophore [Ru(bipy)(CN)4]2- with Yb(III) provides coordination polymers or oligomers containing Ru-CN-Yb bridges; in [K(H2O)4][Yb(H2O)6][Ru(bipy)(CN)4]2.5H2O Ru-->Yb energy-transfer (k > 5 x 10(6) s(-1)) results in partial quenching of the Ru-based luminescence and sensitised near-IR luminescence from the Yb(III) unit.