A facile synthesis and spectral (ir, 1H, 13C, 31P nmr) studies of 2,10-dichloro-6-aryloxy-12H-dibenzo[d,g][1,3,2]dioxaphosphocin 6-sulfides

The synthesis of new 2,10-dichloro-6-aryloxy-12H-dibenzo[d,g][1,3,2]dioxaphosphocin 6-sulfides 4 was achieved in two steps with high yields from the simple materials 5,5′-dichloro-2,2′-dihydroxydiphenyl-methane (1) and thiophosphoryl chloride (2) which produced the key intermediate 2,6,10-trichloro-12H-dibenzo[d,g][1,3,2]dioxaphosphocin 6-sulfide (3) . Treatment of 3 with substituted phenols under phase transfer catalytic (PTC) conditions led to members of 4 . Long range coupling [⁵J_(P,H) = 3.6 Hz] was observed between phosphorus and one of the bridged methylene protons in 4 . A ¹³C nmr analysis revealed ²J_(P,O,C), ³J_(P,O,C) ⁴J(P,O,C) and ⁵J(P,O,C) couplings. All ³¹P nmr chemical shifts for thirteen members of these new heterocycles are reported for the first time. The nmr data are not totally definitive to confirm a boat-chair as the major conformer for the central eight-membered dioxaphosphocin ring, but such a conformer is tentatively suggested as favored.     

The enhanced green fluorescent protein as a tool for the analysis of protein dynamics and localization: local fluorescence study at the single-molecule level

The green fluorescent protein (GFP) has emerged, in recent years, as a powerful reporter molecule for monitoring gene expression, protein localization and protein-protein interaction. Several mutant variants are now available differing in absorption, emission spectra and quantum yield. Here we present a detailed study of the fluorescence properties of the Phe-64-->Leu, Ser-65-->Thr mutant down to the single molecule level in order to assess its use in quantitative fluorescence microscopy and single-protein trafficking. This enhanced GFP (EGFP) is being used extensively as it offers higher-intensity emission after blue-light excitation with respect to wild-type GFP. By means of fluorescence spectroscopy we demonstrate the absence of the neutral form of the chromophore and the lack of photobleaching recovery after ultraviolet light irradiation. Furthermore, we show that the EGFP spectral properties from isolated to densely packed molecules are highly conserved. From these experiments EGFP emerges as an ideal molecule for quantitative studies of intra and intercellular tagged-protein dynamics and fluorescence-activated cell sorting, but not for monitoring single-protein trafficking over extended periods of time.     

Construction and assessment of some perchlorate-selective liquid membrane electrodes

Perchlorate-selective liquid membrane electrodes were developed by incorporating the ion-pair complexes of perchlorate with brucine, cinchonidine, emetine and benzyldimethyltetradecylammonium chloride (zephiramine) in nitrobenzene. The electrodes, which respond to perchlorate ion over the concentration range 1.0–5.0 × 10^?4 M ClO^?₄, have a fast response and wide pH range. The zephiramine-perchlorate electrode was the best in terms of its fast response, wide pH range and high reproducibility of potentials. Most common inorganic and organic anions, except permanganate, do not cause significant interference. Electrodes based on brucine-, emetine- and zephiramine-perchlorate were successfully employed for the direct potentiometric determination of perchlorate in the presence of halides, sulphate, nitrate and chlorate. The cinchonidine-perchlorate electrode showed comparatively poor selectivity.     

Realization of an advanced nozzle concept for compact chemical oxygen iodine laser

Conventional supersonic chemical oxygen–iodine lasers (SCOIL) are not only low-pressure systems, with cavity pressure of 2–3 Torr and Mach number of approximately 1.5, but also are high-throughput systems with a typical laser power per unit evacuation capacity of nearly 1 J/l, thus demanding high capacity vacuum systems which mainly determine the compactness of the system. These conventional nozzle-based systems usually require a minimum of a two-stage ejector system for realization of atmospheric pressure recovery in a SCOIL. Typically for a 500 W class SCOIL, a first stage requires a motive gas flow (air) of 120 gm/s to entrain a laser gas flow of 3 g/s and is capable of achieving the pressure recovery in the range of 60–80 Torr. On the other hand, the second stage ejector requires 4.5 kg/s of motive gas (air) to achieve atmospheric pressure recovery. An advanced nozzle, also known as ejector nozzle, suitable for a 500 W-class SCOIL employing an active medium flow of nearly 12 g/s, has been developed and used instead of a conventional slit nozzle. The nozzle has been tested in both cold as well as hot run conditions of SCOIL, achieving a typical cavity pressure of nearly 10 Torr, stagnation pressure of approximately 85 Torr and a cavity Mach number of 2.5. The present study details the gas dynamic aspects of this ejector nozzle and highlights its potential as a SCOIL pressure recovery device. This nozzle in conjunction with a diffuser is capable of achieving pressure recovery equivalent to a more cumbersome first stage of the pressure recovery system used in the case of a conventional slit nozzle-based system. Thus, use of this nozzle in place of a conventional slit nozzle can achieve atmospheric discharge using a single stage ejector system, thereby making the pressure recovery system quite compact.     

Nonbonded interactions in membrane-active cyclic biopolymers. III. Analogs of valinomycin

Several analogs of valinomycin have been simulated. These are analogs obtained by changing the configuration of the amino acid and hydroxy acid residues one at a time. Nonbonded interactions have been calculated for three conformations of each analog. The electrostatic and polarization contributions to the energy are conformation selective, whereas the Pauli repulsion is the only component which is isomer selective. For the ring chirality considered here the analog of valinomycin having all the three L -valyl residues replaced by D -valyl residues is predicted to be frozen in a “top open” conformation.     

Nanoporous morphology of alumina films prepared by sol–gel dip coating method on alumina substrate

Nanoporous crack free alumina thin films were fabricated in two phases gamma (??) and alpha (??) by sol?Cgel dip coating method. The thickness of the mesoporous films was increased with binder by varying its concentration, and with increasing the number of coating. The porosity, pore size, surface area and phase were controlled by sintering temperature. Interconnected pore structure of 8?C15?nm diameter were successfully prepared by repeating the deposition several times. FESEM, BET, AFM and XRD techniques were employed for the microstructural characterization.