Surfactant enhanced lipase containing films characterized by confocal laser scanning microscopy

An environmentally benign method for the synthesis of noble metal nanoparticles has been reported using aqueous solution of gum kondagogu (Cochlospermum gossypium). Both the synthesis, as well as stabilization of colloidal Ag, Au and Pt nanoparticles has been accomplished in an aqueous medium containing gum kondagogu. The colloidal suspensions so obtained were found to be highly stable for prolonged period, without undergoing any oxidation. SEM–EDXA, UV–vis spectroscopy, XRD, FTIR and TEM techniques were used to characterize the Ag, Au and Pt nanoparticles. FTIR analysis indicates that –OH groups present in the gum matrix were responsible for the reduction of metal cations into nanoparticles. UV–vis studies showed a distinct surface plasmon resonance at 412 and 525 nm due to the formation of Au and Ag nanoparticles, respectively, within the gum network. XRD studies indicated that the nanoparticles were crystalline in nature with face centered cubic geometry. The noble metal nanoparticles prepared in the present study appears to be homogeneous with the particle size ranging between 2 and 10 nm, as evidenced by TEM analysis. The Ag and Au nanoparticles formed were in the average size range of 5.5 ± 2.5 nm and 7.8 ± 2.3 nm; while Pt nanoparticles were in the size range of 2.4 ± 0.7 nm, which were considerably smaller than Ag and Au nanoparticles. The present approach exemplifies a totally green synthesis using the plant derived natural product (gum kondagogu) for the production of noble metal nanoparticles and the process can also be extended to the synthesis of other metal oxide nanoparticles.     

Cephalosporin-3'-diazeniumdiolates: Targeted NO-Donor Prodrugs for Dispersing Bacterial Biofilms

Just say NO to biofilms: NO-donors are used to disperse a bacterial biofilm so that co-administered antibiotics will kill the more susceptible unattached cells. The chemically stable cephalosporin-3'-diazeniumdiolate NO-donor prodrug is activated by bacterial β-lactamases and facilitates this two-step biofilm erradication.     

PIV analysis of merging flow in a simplified model of a rotary kiln

Rotary kilns are used in a variety of industrial applications. The focus in this work is on characterizing the non-reacting, isothermal flow field in a rotary kiln used for iron ore pelletization. A downscaled, simplified model of the kiln is experimentally investigated using particle image velocimetry. Five different momentum flux ratios of the two inlet ducts to the kiln are investigated in order to evaluate its effect on the flow field in general and the recirculation zone in particular. Time-averaged and phase-averaged analyses are reported, and it is found that the flow field resembles that of two parallel merging jets, with the same characteristic flow zones. The back plate separating the inlet ducts acts as a bluff body to the flow and creates a region of reversed flow behind it. Due to the semicircular cross-section of the jets, the wake is elongated along the walls. Conclusions are that the flow field shows a dependence on momentum flux ratio of the jets; as the momentum flux ratio approaches unity, there is an increasing presence of von Kármán-type coherent structures with a Strouhal number of between 0.16 and 0.18. These large-scale structures enhance the mixing of the jets and also affect the size of the recirculation zone. It is also shown that the inclination of the upper inlet duct leads to a decrease in length of the recirculation zone in certain cases.     

The 2-phenylsulfonylethylcarbonyl (PSEC) group for the protection of the hydroxyl function

The PSEC group may be used to protect the hydroxyl function in conjunction with a variety of acid and base labile protecting groups; the PSEC group may be removed by treatment of triethylamine (15 equiv.) in dry pyridine solution within 20 h at 20°C while other base labile protecting groups remained intact.     

The application of 2-(4-chlorophenyl)-sulfonylethoxycarbonyl (CPSEC) group in the synthesis of a DNA segment using the phosphotriester approach

The new base labile CPSEC group has been successfully employed for the protection of the 5′-hydroxyl function to synthesize a “universal Stop codon” DNA sequence: ^5′d(TCAATCAATCA)^3′.     

A practical synthesis of D-erythro-sphingosine using a cross-metathesis approach

Starting from a vinylepoxide, a short and practical synthesis of D-erythro-sphingosine is described. The key transformations are a regioselective opening of the vinylepoxide and an E-selective cross-metathesis, affording the target molecule 5 in steps and 51% overall yield.     

Thermally induced cationic polymerization of divinyl ethers using iodonium and sulfonium salts

Cationic polymerization of diethyleneglycoldivinyl ether was thermally induced by diphenyliodonium, alkylbenzylsulfonium, and phenacyltetramethylenesulfonium salts. The reactivity was enhanced by using free radical sources in combination with diphenyliodonium or phenacyltetramethylenesulfonium salts. Even at low onium salt concentrations extremely reactive formulations could be obtained, e.g., the polymerization was complete within 1 minute at 100°C when using the most reactive salts. Polymerizations were induced at temperatures ranging from 50 to 180°C. The Counterion, Supplied by the onium salts, strongly influenced the appearance of the resulting crosslinked polymer: salts containing SbF⁻₆ usually gave highly discolored samples due to the large heat evolution during polymerization whereas polymerization with PF⁻₆ proceeded smoother resulting in transparent, uncolored polymers. The purity of the monomer greatly affected the initiation by the diphenyliodonium and phenacyltetramethylenesulfonium salts. Adventitious radical sources, e. g., hydroperoxides on oxidized monomer, lowered the activation temperature but also led to poor storage stability of these formulations.     

High-pressure ammonia adsorption and dissociation on clean fe(111) and oxygen-precovered fe(111) studied by sum frequency generation vibrational spectroscopy

The adsorption of gases N2, H2, O2, and NH3 that play a role in ammonia synthesis have been studied on the Fe(111) crystal surface by Sum Frequency Generation (SFG) vibrational spectroscopy using an integrated ultrahigh vacuum/high-pressure system. SFG spectra are presented for the dissociation intermediates, NH2 ( approximately 3325 cm-1) and NH ( approximately 3235 cm-1) under high pressure of ammonia (200 Torr) on the clean Fe(111) surface. Addition of 0.5 Torr of oxygen to 200 Torr of ammonia does not significantly change the bonding of dissociation intermediates to the surface. However, it leads to a phase change of nearly 180 degrees between the resonant and nonresonant second-order nonlinear susceptibility of the surface, demonstrated as a reversal of the SFG spectral features. Heating the surface in the presence of 200 Torr of ammonia and 0.5 Torr of oxygen reduces the oxygen coverage, which can be seen from the SFG spectra as another relative phase change of 180 degrees . The reduction of the oxide is also supported by Auger electron spectroscopy. The result suggests that the phase change of the spectral features could serve as a sensitive indicator of the chemical environment of the adsorbates. Clean Fe(111) is found to have a large SFG nonresonant signal. The magnitude of the nonresonant signal was dependent on the adsorption species; O2 and N2 decrease, while H2 and NH3 increase the SFG nonresonant signal. The change in nonresonant signal is correlated to the change in work function for Fe(111) upon adsorption. Adsorption-induced changes in the SFG nonresonant signal was used as an indicator of surface conditions and to monitor surface reactions.     

Surface properties of hydrous manganite (gamma-MnOOH). A potentiometric, electroacoustic, and X-ray photoelectron spectroscopy study

The acid-base characteristics of the manganite (gamma-MnOOH) surface have been studied at pH above 6, where dissolution is negligible. Synthetic microcrystalline particles of manganite were used in the experiments. From potentiometric titrations, electrophoretic mobility measurements, and X-ray photoelectron spectroscopy (XPS), a one pK(a) model was constructed that describes the observed behavior. The data show no ionic strength effect at pH < 8.2, which is the pH at the isoelectric point (pH(iep)), but ionic strength effects were visible above this pH. To explain these observations, Na(+) ions were suggested to form a surface complex. The following equilibria were established: =MnOH(2)(+1/2) right harpoon over left harpoon =MnOH(-)(1/2) + H(+), log beta(0) (intr.) = -8.20; =MnOH(2)(+1/2) + Na(+) right harpoon over left harpoon =MnOHNa(+1/2) + H(+), log beta(0) (intr.) = -9.64. The excess of Na(+) at the surface was supported by XPS measurements of manganite suspensions containing 10 mM NaCl. The dielectric constant of synthetic manganite powder was also determined in this study.