Gold oxide as a protecting group for regioselective surface chemistry

Selective modification of electrode surfaces is a vital step in the development of many practical applications of self-assembled monolayers (SAMs). This paper describes a protection-deprotection strategy similar to that commonly utilized in organic synthesis, with gold oxide as a protecting layer, to direct self-assembly on one gold electrode in the presence of another.     

Upgrade of MacCHESS facility for X‐ray scattering of biological macromolecules in solution

X‐ray scattering of biological macromolecules in solution is an increasingly popular tool for structural biology and benefits greatly from modern high‐brightness synchrotron sources. The upgraded MacCHESS BioSAXS station is now located at the 49‐pole wiggler beamline G1. The 20‐fold improved flux over the previous beamline F2 provides higher sample throughput and autonomous X‐ray scattering data collection using a unique SAXS/WAXS dual detectors configuration. This setup achieves a combined q‐range from 0.007 to 0.7 Å^?1, enabling better characterization of smaller molecules, while opening opportunities for emerging wide‐angle scattering methods. In addition, a facility upgrade of the positron storage ring to continuous top‐up mode has improved beam stability and eliminated beam drift over the course of typical BioSAXS experiments. Single exposure times have been reduced to 2 s for 3.560 mg ml^?1 lysozyme with an average quality factor I/σ of 20 in the Guinier region. A novel disposable plastic sample cell design that incorporates lower background X‐ray window material provides users with a more pristine sample environment than previously available. Systematic comparisons of common X‐ray window materials bonded to the cell have also been extended to the wide‐angle regime, offering new insight into best choices for various q‐space ranges. In addition, a quantitative assessment of signal‐to‐noise levels has been performed on the station to allow users to estimate necessary exposure times for obtaining usable signals in the Guinier regime. Users also have access to a new BioSAXS sample preparation laboratory which houses essential wet‐chemistry equipment and biophysical instrumentation. User experiments at the upgraded BioSAXS station have been on‐going since commissioning of the beamline in Summer 2013. A planned upgrade of the G1 insertion device to an undulator for the Winter 2014 cycle is expected to further improve flux by an order of magnitude.     

Two-stage network DEA: when intermediate measures can be treated as outputs from the second stage

This paper investigates efficiency measurement in a two-stage data envelopment analysis (DEA) setting. Since 1978, DEA literature has witnessed the expansion of the original concept to encompass a wide range of theoretical and applied research areas. One such area is network DEA, and in particular two-stage DEA. In the conventional closed serial system, the only role played by the outputs from Stage 1 is to behave as inputs to Stage 2. The current paper examines a variation of that system. In particular, we consider settings where the set of final outputs comprises not only those that result from Stage 2, but can include, in addition, certain outputs from the previous (first) stage. The difficulty that this situation creates is that such outputs are attempting to play both an input and output role in the same stage. We develop a DEA-based methodology that is designed to handle what we term ‘time-staged outputs’. We then examine an application of this concept where the DMUs are schools of business.     

Oligomeric liquid crystals: From monomers to trimers

A homologous series of linear liquid crystal trimers, the 4,4′-bis[ω-(4-methoxyazobenzene-4′-yloxy)alkoxy]azobenzenes, has been synthesized and characterized. The transitional properties of the trimers are compared with those of the corresponding series of dimers, the α,ω-bis(4-methoxyazobenzene-4′-oxy)alkanes, and monomers, the 4-methoxy-4′-alkoxyazobenzenes. Characteristically pronounced odd-even effects were seen for the transitional properties of both dimers and trimers on varying the spacer lengths. The clearing temperatures of the trimers were higher than those of the corresponding dimers, but as the length of the flexible spacers was increased this difference became rather small. The ratios of T _NI, and ΔS _NI/R for monomer:dimer and dimer:trimer are discussed. These are very similar to reported values for similar materials, suggesting that there may be a rather general relationship between the transitional properties of liquid crystal oligomers as the number of mesogenic units is increased.     

Simulation studies of dipole correlation in the isotropic liquid phase

The Kirkwood correlation factor g₁ determines the preference for local parallel or antiparallel dipole association in the isotropic phase. Calamitic mesogens with longitudinal dipole moments and Kirkwood factors greater than 1 have an enhanced effective dipole moment along the molecular long axis. This leads to higher values of Δ? in the nematic phase. This paper describes state-of-the-art molecular dynamics simulations of two calamitic mesogens 4-(trans-4-n-pentylcyclohexyl)benzonitrile (PCH5) and 4-(trans-4-n-pentylcyclohexyl)chlorobenzene (PCH5-Cl) in the isotropic liquid phase using an all-atom force field and taking long range electrostatics into account using an Ewald summation. Using this methodology, PCH5 is seen to prefer antiparallel dipole alignment with a negative g₁ and PCH5-Cl is seen to prefer parallel dipole alignment with a positive g₁; this is in accordance with experimental dielectric measurements. Analysis of the molecular dynamics trajectories allows an assessment of why these molecules behave differently.     

Facile Tuning of Luminescent Platinum(II) Schiff Base Complexes from Yellow to Near‐Infrared: Photophysics,Electrochemistry, Electrochemiluminescence and Theoretical Calculations

The photophysical and related properties of platinum(II) Schiff base complexes can be finely and predictably tuned over a wide range of wavelengths by small and easily implemented changes to ligand structure. A series of such complexes, differing only in the number and positioning of methoxy substituents on the phenoxy ring, were synthesised and their photophysical, electrochemical and electrochemiluminescent (ECL) properties investigated. Theoretical calculations were performed in order to gain further insight into the relationship between structure and properties in these materials. By positioning methoxy groups para and/or ortho to either the imine or the oxygen group on the ligand, electron density could be directed selectively toward the LUMO or HOMO as required. This allowed the emission colour (both photoluminescent and electrochemiluminescent) to be tuned over a wide range between 587 and 739 nm. The variation in orbital energies was also manifested in the positions of the absorption bands and the redox properties of the complexes, as well as in the NMR shifts for the uncoordinated ligands. All reported complexes displayed intense electrochemiluminescence (ECL), which could be initiated either by annihilation or co‐reactant pathways. The relationship between the electrochemical and photophysical properties and the efficiency of the ECL is discussed. For two of the complexes solid‐state ECL could be generated from electrodeposited layers of the complex.     

Anticancer Potency and Multidrug‐Resistant Studies of Self‐Assembled Arene–Ruthenium Metallarectangles

A suite of three tetraruthenium metallacycles have been obtained from [2+2] self‐assemblies between N,N′‐Di‐(4‐pyridyl)‐1,4,5,8‐naphthalenetetracarbo–xydiimide ( 4 ) and one of the three dinuclear arene ruthenium clips, (η⁶‐p‐iPrC₆H₄Me)₂Ru₂(OO∩OO)][OTf]₂ (OO∩OO=oxalate 1 , 2,5‐dioxydo‐1,4‐benzoquinonato (dobq) 2 , 5,8‐dihydroxy‐1,4‐naphthaquinonato (donq) 3 ; OTf=triflate). All complexes were isolated in good yield (>85 %) as triflate salts and were fully characterized by using ¹H NMR and UV/Vis spectroscopies, and high‐resolution electrospray mass spectrometry. A single crystal of the metallarectangle 5 was suitable for X‐ray diffraction structural characterization. The biological activities of the metallacycles were determined by using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide (MTT) assays, establishing their in vitro anticancer properties. Our results show that for the AGC (gastric cancer) cell lines, the cytotoxicity of (donq)‐containing SCC 7 exceeds that of cisplatin, which was used as a control. For HCT15 (colon cancer) cell lines, the cytotoxicity is comparable to both cisplatin and doxorubicin. An in vivo hollow fiber model was used to show growth‐inhibitory activity against HCT15 and image‐based cytometry experiments indicated that 7 induced apoptosis as the mode of cell death. Complex 7 also showed significant antitumor activity for multidrug‐resistant HCT15/CLO2 cell lines, for which doxorubicin was ineffective.     

Entry into 6-Methoxy-D(+)-tryptophans. Stereospecific Synthesis of 1-Benzenesulfonyl-6-methoxy-D(+)-tryptophan Ethyl Ester

A strategy for the synthesis of optically active ring-A methoxylated indole alkaloids which employs the Moody azide/Schollkopf chiral auxiliary protocol has resulted in the successful preparation of 1-benzenesulfonyl-6-methoxy-D(+)-tryptophan ethyl ester 16. This amino ester is required for the synthesis of Alstonia bisindole alkaloids including macralstonine 2 via an enantiospecific Pictet-Spengler reaction.     

Polymerization and Copolymerization Studies of Orthoacrylates: A Novel Class of Acrylic Esters

Although ortho-esters constitute a well-known class of organic compounds, the orthoacrylates were unknown prior to a report from these laboratories in 1972. To date, this novel class of acrylic esters has not been investigated as polymerization monomers. We report here polymerization and copolymerization studies of representative members of this class of compounds. Although the orthoacrylates studied did not polymerize in the presence of conventional cationic initiators nor radical initiators, they did respond to radical-initiated copolymerization with a variety of conventional vinyl monomers. Their corresponding reactivity ratios were determined, as well as the Q and e parameters. Monomer syntheses and characterization are reported, as well as structural and properties studies on the copolymers.     

Field Desorption Mass Spectral Data for Oligomers up to 2400 Amu

Field desorption mass spectra of oligomers show peaks of mass up to 2400 amu.