7-Amino-5-imino-8(5H)-quinolones, 6-Amino-8-imino-5(8H)-quinolones and 7-Alkyl-4,6-dihydroxy-5,8-quinolinediones as potential antiprotozoal agents

Oxidation of 7-amino-8-hydroxyquinoline-5-sulfonic acid with silver oxide in dimethylformamide and in the presence of arylamines provided a series of 7-amino-5-arylimino-8(5H)-quinolones (VIIIb). Reaction of 8-dialkylamino-5,6-quinolinediones with triethyloxonium tetrafluoborate gave a series of unstable but synthetically useful enol ethers. These reacted with amines to give 6-amino-8-imino-5(8H)-quinolones, isolated and characterized as tetrafluoborate salts (XIa). Proton magnetic resonance studies showed these to be vinylogous amidinium salts, analogous to those previously obtained with 2-amino-1,4-naphthoquinone imines. 4,6-Dihydroxy-5,8-quinolinedione underwent free radical alkylation to give a 7-alkyl-4,6-dihydroxy-5,8-quinolinedione. Evaluation of the new compounds against various Plasmodium species in rodents, birds and mosquitoes revealed no significant antimalarial activity.     

Determination of zinc in plant materials using ion-exchange chromatography

The objective of this investigation was to develop a rapid and accurate method for the determination of zinc in plant materials. An ion-exchange separation technique to eliminate interferences in the Zincon procedure for zinc is described. Comparison with the A.O.A.C. method and evaluation of zinc recovery studies show the proposed method to be satisfactory for the analysis of microgram amounts of zinc in plant materials.     

Assessing helical protein interfaces for inhibitor design

Structure-based design of synthetic inhibitors of protein-protein interactions (PPIs) requires adept molecular design and synthesis strategies as well as knowledge of targetable complexes. To address the significant gap between the elegant design of helix mimetics and their sporadic use in biology, we analyzed the full set of helical protein interfaces in the Protein Data Bank to obtain a snapshot of how helices that are critical for complex formation interact with the partner proteins. The results of this study are expected to guide the systematic design of synthetic inhibitors of PPIs. We have experimentally evaluated new classes of protein complexes that emerged from this data set, highlighting the significance of the results described herein.     

Crystal Structure-Guided Design of Bisubstrate Inhibitors and Photoluminescent Probes for Protein Kinases of the PIM Family

We performed an X-ray crystallographic study of complexes of protein kinase PIM-1 with three inhibitors comprising an adenosine mimetic moiety, a linker, and a peptide-mimetic (d-Arg)₆ fragment. Guided by the structural models, simplified chemical structures with a reduced number of polar groups and chiral centers were designed. The developed inhibitors retained low-nanomolar potency and possessed remarkable selectivity toward the PIM kinases. The new inhibitors were derivatized with biotin or fluorescent dye Cy5 and then applied for the detection of PIM kinases in biochemical solutions and in complex biological samples. The sandwich assay utilizing a PIM-2-selective detection antibody featured a low limit of quantification (44 pg of active recombinant PIM-2). Fluorescent probes were efficiently taken up by U2OS cells and showed a high extent of co-localization with PIM-1 fused with a fluorescent protein. Overall, the developed inhibitors and derivatives represent versatile chemical tools for studying PIM function in cellular systems in normal and disease physiology.     

Enhanced rear‐side reflection and firing‐stable surface passivation of silicon solar cells with capping polymer films

Low refractive index polymer materials have been investigated with a view to form the back surface mirror of advanced silicon solar cells. SiO_x:H or AlO_y SiO_x:H polymer films were spun on top of an ultra‐thin (<10 nm) atomic‐layer‐deposited (ALD) Al₂O₃ layer, itself deposited on low‐resistivity (1 Ω cm) p‐type crystalline silicon wafers. These double‐layer stacks were compared to both ALD Al₂O₃ single layers and ALD Al₂O₃/plasma‐enhanced chemical vapour deposited (PECVD) SiN_x stacks, in terms of surface passivation, firing stability and rear‐side reflection. Very low surface recombination velocity (SRV) values approaching 3 cm/s were achieved with ALD Al₂O₃ layers in the 4–8 nm range. Whilst the surface passivation of the single ALD Al₂O₃ layer is maintained after a standard firing step typical of screen printing metallisation, a harsher firing regime revealed an enhanced thermal stability of the ALD Al₂O₃/SiO_x:H and ALD Al₂O₃/AlO_y SiO_x:H stacks. Using simple two‐dimensional optical modelling of rear‐side reflection it is shown that the low refractive index exhibited by SiO_x:H and AlO_y SiO_x:H results in superior optical performance as compared to PECVD SiN_x, with gains in photogenerated current of ～0.125 mA/cm² at a capping thickness of 100 nm. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electron spin resonance studies of spin-labelled polymers—VIII: Relaxation processes in low density polyethylene

Low density polyethylene was spin-labelled with an oxazolidine-N-oxyl group. Correlation times for the motion of the label were calculated both in the slow-motion region and in the motionally-narrowed region. In the latter situation, the central line shape was successfully simulated. A correlation map revealed the α- and β-relaxation processes in solid polyethylene, with activation energies of 48 and 28 kJ mol^?1, respectively. The segmental reorientation processes of polyethylene in the melt and in solution had activation energies of 15·2 and 22·9 kJ mol^?1, respectively. Taking into account the effect of viscous drag of the solvent, the two activation energies were almost the same suggesting that the same relaxation process occurs in the bulk molten polymer and in the isolated molecule. The model compound 2,2′,5,5′-tetramethyl-3-oxazolidinyloxy was synthesized and used as a spin-probe in the polymer. The spin-probe experiments gave a transition temperature attributed to the γ-relaxation.     

The Yang-Mills measure in the Kauffman bracket skein module

For each closed, orientable surface , we construct a local, diffeomorphism invariant trace on the Kauffman bracket skein module . The trace is defined when |t| is neither 0 nor 1, and at certain roots of unity. At t = − 1, the trace is integration against the symplectic measure on the SU(2) character variety of the fundamental group of . Received: June 2, 2000     

Numerical simulation of transient response of heat transfer from a hot-wire anemometer transducer

Both the steady state and transient response of the Nusselt number to variations in Reynolds number over the range 1 to 40 are given by the analysis of a time dependent numerical simulation of a hot-wire anemometer transducer described here. Transducer response can be modelled suitably by considering the system to consist of a phase independent non-linearity followed by a non-linear differential equation whose coefficient (approximate time constant) is Nusselt number dependent. Errors associated with slip flow and free convection constrain the minimum size of a hot-wire which may be used in calibration anemometry while the wire thermal inertia and, to a lesser extent, the response of the Nusselt number to Reynolds number limits the use of large diameter wires. Thus, although the tendency has been to use finer and finer wires, the basic fluid mechanics suggests that a compromise in the choice of the wire diameter is appropriate. Thus development of even more sophisticated hot-wire anemometer control systems as well as accurate calibration techniques for measurement in flows containing large amplitude high frequency turbulence is required