Easy-dispersible poly(glycidyl phenyl ether)-functionalized graphene sheets obtained by reaction of "living" anionic polymer chains

Excellent dispersion of functionalized graphene (FG) sheets in polystyrene was achieved relying on the reaction of "living" poly(glycidyl phenyl ether) chains onto graphene sheets. The physical aging of polystyrene was substantially accelerated by the presence of FG sheets at low filler content, retaining film transparency and increasing the electrical conductivity.     

A carrier protein strategy yields the structure of dalbavancin

Many large natural product antibiotics act by specifically binding and sequestering target molecules found on bacterial cells. We have developed a new strategy to expedite the structural analysis of such antibiotic-target complexes, in which we covalently link the target molecules to carrier proteins, and then crystallize the entire carrier-target-antibiotic complex. Using native chemical ligation, we have linked the Lys-D-Ala-D-Ala binding epitope for glycopeptide antibiotics to three different carrier proteins. We show that recognition of this peptide by multiple antibiotics is not compromised by the presence of the carrier protein partner, and use this approach to determine the first-ever crystal structure for the new therapeutic dalbavancin. We also report the first crystal structure of an asymmetric ristocetin antibiotic dimer, as well as the structure of vancomycin bound to a carrier-target fusion. The dalbavancin structure reveals an antibiotic molecule that has closed around its binding partner; it also suggests mechanisms by which the drug can enhance its half-life by binding to serum proteins, and be targeted to bacterial membranes. Notably, the carrier protein approach is not limited to peptide ligands such as Lys-D-Ala-D-Ala, but is applicable to a diverse range of targets. This strategy is likely to yield structural insights that accelerate new therapeutic development.     

Tuning of the emission efficiency and HOMO-LUMO band gap for ester-functionalized {Al(salophen)(H2O)2}+ blue luminophors

A series of [AlL(H(2)O)(2)(NO(3))] complexes, with L standing for an ester substituted salophen-type ligand, has been synthesized, and the luminescence properties have been investigated. These derivatives differ by the nature of the ester-R group introduced at the C5 position of their salicylidene rings (i.e., phenyl, 7a,a'; naphthyl, 7b,b'; pentafluorophenyl, 7c,c'; and p-nitrophenyl, 7d) and by the bis-imino bridge (i.e., 1,2- phenylene, 7a-d; and 1,2-naphthalene, 7a'-c'). All the complexes are characterized by luminescence in the blue range, the chemical diversity having no effect on the emission wavelength (480-485 nm). However, the emission efficiency was found to be strongly dependent on the Schiff-base ligand with quantum yields ranging from ? = 22% to 44%, the highest values being for the salophen derivatives with the electron-withdrawing ester-R groups (7a, 34%; 7a', 23%; 7b, 31%; 7b', 22%; 7c, 40%; 7c', 29%, and 7d, 44%). Both the electrochemical data and DFT calculations show that the HOMO-LUMO band gap is modified as a function of the ester R group (from 2.92 to 3.16 eV, based on the redox potentials). The crystal structures for the N,N'-bis(5-(phenoxycarbonyl)salicylidene)-1,2-phenylenediamine and the N,N'-bis(5-(p-nitrophenoxycarbonyl)salicylidene)-1,2-phenylenediamine aluminum complexes (7a and 7d) are reported.     

Novel class of non-ionic monocatenary and bolaform alkylglycoside surfactants. Synthesis by microwave-assisted glycosylation and olefin cross-metathesis or by ‘click-chemistry’: physicochemical studies

We develop herein the synthesis of a new class of monocatenary and bolaform surfactants from d-glucose, d-galactose and lactose. Two main pathways have been investigated: microwave-assisted glycosylation followed by olefin cross-metathesis, and the one-step click-chemistry methodology. Tensioactive properties of these new compounds have been studied in order to characterize the physicochemical behaviour of these new carbohydrate-based compounds in water.     

Temperature dependence of electron spin resonance in CaCu3Ti4O12 substituted with transition metal elements

The temperature dependence of the electron spin resonance (ESR) spectrum of copper in CaCu₃Ti₄O₁₂ (CCTO) polycrystalline samples doped with transition metal elements Mn, Fe, Ni is reported. The frequency dependence of the dielectric constant of the sample is also reported at room temperature. While the dielectric constant of undoped CCTO samples reaches ～10,000, it is found one hundred times lower in samples doped with only 0.5 or 1% of Mn or Fe. Copper is confirmed to give a g = 2.14 signal at room temperature for substituted and unsubstituted samples. Below the antiferromagnetic transition that occurs near 25 K, the signal is found shifted down to low fields for all samples. However the downshift is 10–20 times more important in Mn and Fe-doped samples compared to undoped or Ni-doped CCTO. ESR results in an undoped CCTO thin film grown by pulse laser deposition are also reported. While in the low-temperature antiferromagnetic phase the spectrum is multi-line and magnetic-field-orientation-dependent, it reduces to a narrow single line, independent of the orientation of the magnetic field, in the upper paramagnetic phase, similar to the undoped polycrystalline sample. All doped samples display much broader response in the upper phase. The results are discussed within the framework of the relationship between the high effective dielectric constant and the electrical conductivity of CCTO bulk.     

Inter-comparison of 2 microm Heterodyne Differential Absorption Lidar, Laser Diode Spectrometer, LICOR NDIR analyzer and flasks measurements of near-ground atmospheric CO2 mixing ratio

Remote sensing and in situ instruments are presented and compared in the same location for accurate CO(2) mixing ratio measurements in the atmosphere: (1) a 2.064 microm Heterodyne DIfferential Absorption Lidar (HDIAL), (2) a field deployable infrared Laser Diode Spectrometer (LDS) using new commercial diode laser technology at 2.68 microm, (3) LICOR NDIR analyzer and (4) flasks. LDS, LICOR and flasks measurements were made in the same location, LICOR and flasks being taken as reference. Horizontal HDIAL measurements of CO(2) absorption using aerosol backscatter signal are reported. Using new spectroscopic data in the 2 microm band and meteorological sensor measurements, a mean CO(2) mixing ratio is inferred by the HDIAL in a 1 km long path above the 15m height location of the CO(2) in situ sensors. We compare HDIAL and LDS measurements with the LICOR data for 30 min of time averaging. The mean standard deviation of the HDIAL and the LDS CO(2) mixing ratio results are 3.3 ppm and 0.89 ppm, respectively. The bias of the HDIAL and the LDS measurements are -0.54 ppm and -0.99 ppm, respectively.     

Diffusion coefficient and shear viscosity of rigid water models

We report the diffusion coefficient and viscosity of popular rigid water models: two non-polarizable ones (SPC/E with three sites, and TIP4P/2005 with four sites) and a polarizable one (Dang-Chang, four sites). We exploit the dependence of the diffusion coefficient on the system size (Yeh and Hummer 2004 J. Phys. Chem. B 108 15873) to obtain the size-independent value. This also provides an estimate of the viscosity of all water models, which we compare to the Green-Kubo result. In all cases, a good agreement is found. The TIP4P/2005 model is in better agreement with the experimental data for both diffusion and viscosity. The SPC/E and Dang-Chang models overestimate the diffusion coefficient and underestimate the viscosity.     

Snap Together Bonds for Amine Capturing – New Spectroscopic and Amperometric Sensors

Summary: A conjugated polymer ( P1 ) containing a pendant aldehyde was anodically prepared on ITO electrodes. Aminothiophenes could be captured by reacting with an aldehyde group located along the polymer backbone resulting in a robust azomethine bond. This was confirmed both spectroscopically and electrochromically. P1 undergoes absorbance and fluorescence bathochromic shifts when an aminothiophene is covalently linked to the aldehyde resulting from azomethine formation. Both the absorbance and fluorescence shifts are dependent on the aminothiophene used to form the azomethine bond.