Simultaneously multiply-configurable or superposed molecular logic systems composed of ICT (internal charge transfer) chromophores and fluorophores integrated with one- or two-ion receptors

Integrated "ICT chromophore-receptor" systems show ion-induced shifts in their electronic absorption spectra. The wavelength of observation can be used to reversibly configure the system to any of the four logic operations permissible with a single input (YES, NOT, PASS 1, PASS 0), under conditions of ion input and transmittance output. We demonstrate these with dyes integrated into Tsien's calcium receptor, 1-2. Applying multiple ion inputs to 1-2 also allows us to perform two- or three-input OR or NOR operations. The weak fluorescence output of 1 also shows YES or NOT logic depending on how it is configured by excitation and emission wavelengths. Integrated "receptor(1)-ICT chromophore-receptor(2)" systems 3-5 selectively target two ions into the receptor terminals. The ion-induced transmittance output of 3-5 can also be configured via wavelength to illustrate several logic types including, most importantly, XOR. The opposite effects of the two ions on the energy of the chromophore excited state is responsible for this behaviour. INHIBIT and REVERSE IMPLICATION are two of the other logic types seen here. Integration of XOR logic with a preceding OR operation can be arranged by using three ion inputs. The fluorescence output of these systems can be configured via wavelength to display INHIBIT or NOR logic under two-input conditions. The superposition or multiplicity of logic gate configurations is an unusual consequence of the ability to simultaneously observe multiple wavelengths.     

Stereocontrolled formation of beta-glucosides and related linkages in the absence of neighboring group participation: influence of a trans-fused 2,3-O-carbonate group

[reaction: see text] Phenyl 4,6-di-O-benzyl-2,3-O-carbonyl-beta-D-glucothiopyranoside and the regiosiomeric phenyl 2,6-di-O-benzyl-3,4-O-carbonyl-beta-D-glucothiopyranoside were prepared and studied as glucosyl donors at -60 degrees C in dichloromethane with preactivation by 1-benzenesulfinyl piperidine before addition of the acceptor alcohol. The 2,3-O-carbonate protected donor showed moderate to excellent beta-selectivity under these conditions depending on the acceptor employed, thereby providing a means for 1,2-trans-equatorial glycosidic bonds without recourse to neighboring group participation and its associated problem of ortho ester formation. In contrast, the 3,4-O-carbonate protected donor showed moderate to no beta-selectivity under the conditions employed. The results obtained in this study with carbonate protected glucopyranosyl donors are contrasted with those obtained previously in the manno- and rhamnopyranosyl series when the 2,3-O-carbonate protected is alpha-selective and the 3,4-O-carbonate is beta-selective.     

Dynamics of curved DNA molecules: prediction and experiment

We have developed a quantitative predictive model capable of describing the dynamics of migration of intrinsically curved DNA fragments on polyacrylamide gels. The model takes into account structural features of DNA, end-to-end distance, screening of hydrodynamic interactions, ionic strength of buffer, electrostatic persistence length, structural fluctuations of the macromolecule, counter condensation, and variation of dielectric constant and viscosity of water with MPD. In doing so, we have also addressed a decade old issue on the effect of the organic solvent 2-methyl-2,4-pentanediol on gel migration of phased A-tracts. We show here that A-tract-solvent interactions are less favored compared with A-tract-A-tract and solvent-solvent interactions.     

High surface area silicon carbide from rice husk: A support material for catalysts

Ultrafine -SiC with high surface area (150 m² g^–1) has been synthesized by inflight processing of charred rice husk in a r.f. plasma reactor operating at atmospheric pressure. The plasma-synthesized particles were doped with platinum (1%) and tested as a catalytic support material. The catalyst (1% Pt doped -SiC) showed 100% conversion of CO to CO₂ at a temperature as low as 175°C.     

High-performance liquid chromatographic separation and immunological characterization of soluble bovine viral diarrhea virus antigen

Sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Western blot analysis of the protein extracts from bovine viral diarrhea virus (BVDV, Singer strain) infected primary calf testicle cells (soluble antigen) showed the presence of four virus specific polypeptides of 105, 90, 84 and 67 kiloDaltons (kD) the 84-kD being the most abundant. Anion-exchange high-performance liquid chromatography (HPLC) of soluble antigen separated the virus specific polypeptides in individual peaks while the gel permeation HPLC collected all of them in a single protein aggregate peak of 290 kD. Except for the 84-kD polypeptide peak in anion-exchange HPLC, all peak fractions were found to be heterogeneous in nature having more than one polypeptide. Analysis of the antisera raised against the peaks having antigen activity showed that antisera against the 84-kD polypeptide peak did not neutralise BVDV while those against the fractions containing the 90- and 105-kD polypeptides neutralised the virus.     

Cationic vesicles as chiral selector for enantioseparations of nonsteroidal antiinflammatory drugs by micellar electrokinetic chromatography

A vesicle-forming chiral cationic surfactant (1R,2S)-(-)-N-dodecyl-N-methyl-ephedrinium bromide was evaluated as a pseudo-stationary phase in micellar electrokinetic chromatography (MEKC) for enantioseparation of eight non-steroidal anti-inflammatory drugs e.g., carprofen, flurbiprofen, fenoprofen, ibuprofen, indoprofen, ketoprofen, naproxen and suprofen by capillary electrophoresis. The effects of varying experimental conditions such as pH and concentration of surfactant in the running buffer on the enantiomer separation of the drugs are reported. A mixture of five of the above drugs was separated and each enantiomeric pair was also separated simultaneously in a single run by use of the surfactant. The strong electrostatic interactions between the analytes and the vesicles seemed to have a major role in the enantiomeric separation of the profens.     

Charge and salt-driven reentrant order-disorder and gas-solid transitions in charged colloids

Monte Carlo simulations have been performed for aqueous charged colloidal suspensions as a function of effective charge density (sigma) on the particles and salt concentration C(s). We vary the effective charge density in our simulations over a range where a reentrant solid-liquid transition in suspensions of silica and polymer latex particles has been reported by Yamanaka et al. (Phys. Rev. Lett. 80 (1998) 5806). We show that at low ionic strengths a homogeneous liquid-like ordered suspension undergoes crystallization upon increasing sigma. Further increase in sigma resulted once again in a disordered state, which is in agreement with experimental observations. In addition to this reentrant order-disorder transition, we observe an inhomogeneous-to-homogeneous transition in our simulations when salt is added to the disordered inhomogeneous state. This inhomogeneous-to-homogeneous disordered transition is analogous to the solid-gas transition of atomic systems and has not yet been observed in charged colloids. The reported experimental observations on charged colloidal suspensions are discussed in the light of present simulation results.     

Determination of Hormones and Non-ionic Surfactant Degradation Products in Small-Volume Aqueous Samples from Soil Columns Using LC-ESI-MS-MS and GC-MS

The leaching of two estrogens, 17β-estradiol and estrone, and two degradation products of non-ionic surfactants, octylphenol and nonylphenol, through a soil column were studied to estimate their transport behavior. Different concentration methods (lyophilization, solid phase extraction, and liquid–liquid extraction) were evaluated for analyzing these compounds in small effluent fractions (30–50 mL) collected. Liquid chromatography-mass spectrometry (LC-MS-MS) and gas chromatography-mass spectrometry (GC-MS) were employed for quantitative analysis of these compounds. After comparison, the lyophilization-LC-MS-MS method was found to be best suited for the analysis of the two estrogen hormones and the liquid–liquid extraction-GC-MS method best for the analysis of the two phenols in small samples in the soil column study. Because of their high sorption capacity, these compounds were mostly sorbed in the upper part of the soil column and were difficult to detect in column effluent.