Ultrafast intermolecular electron transfer dynamics: Perylene in electron-accepting micellar medium

The dynamics of ultrafast photoinduced intermolecular electron transfer (ET) from the excited singlet (S1) state of perylene (Pe) to an electron-accepting cationic surfactant molecule, N-cetylpyridinium chloride (CPC), in aqueous micellar solutions has been investigated using the femtosecond transient absorption spectroscopic technique with temporal resolution of 120 fs. The Pe molecule is localized at or near the micellar surface, where it coexists with the pyridinium moieties (headgroups of the micelle) of the surfactant molecule. Following photoexcitation of Pe, an electron is transferred to the neat and geometrically restricted headgroup of the micelle. Dynamics of the forward ET process as well as the geminate recombination or back ET (BET) process have been followed by monitoring the temporal evolution of the S1 state of Pe and the cation radical of Pe (Pe*+), respectively. The multiexponential forward ET process indicates that the ET dynamics is highly correlated with the spatial distributions of the micellar headgroups around a donor Pe molecule and thus dependent on the donor-acceptor distance. The distance-dependent ET and BET rates have been calculated following the method of Weidemaier and Fayer (J. Chem. Phys. 1995, 102, 3820) to get the best fit parameters for the multiexponetial temporal profiles for the S1 state of Pe as well as Pe*+. Because the acceptor is a constituent of the neat micellar medium, their confinement on the surface of the microheterogeneous medium provides a very large concentration such that, even though the forward transfer rate is 0.06 ps(-1) at the distance of closest approach, the ET process is complete within a 200-ps time domain. If the concepts of distribution of ET distances are utilized, the possible role of material diffusion on the kinetics of forward ET is ruled out. This is an experimental study to show, for the first time, the ultrafast distance-dependent light-induced ET dynamics following both the excited state of the donor and the cation radical formed in an ET process using the transient absorption spectroscopic technique in a self-reactive restrictive environment.     

The influence of inert solids on ethanol production by Saccharomyces cerevisiae

The catalytic role of various inert solid supports on acceleration of alcohol fermentation by Saccharomyces cerevisiae was investigated. The enhanced rate of alcohol production was dependent on the nature of the support as well as on the amount used. Among all the tested supports, chitosan flakes showed the maximum yield of alcohol (93% of theoretical yield). This higher rate of alcohol production was associated with the twofold increase in the activity of alcohol dehydrogenase over control. Our results suggest that the addition of a small fraction of solids in submerged fermentations to facilitate cell anchorage for enhanced metabolic activity is easier and more economical compared to cell immobilization processes. IICT Communication No. 4266. Some of the results in this article are covered under a patent.     

A liquid chromatography–tandem mass spectrometry method for the quantitation of actarit in rabbit plasma: application to pharmacokinetics and metabolic stability

Actarit (ATR), 4‐acetylaminophenylacetic acid is an orally effective disease‐modifying anti‐rheumatic drug widely prescribed for the treatment of rheumatoid arthritis. The present study demonstrates the first report on a selective and sensitive liquid chromatography–tandem mass spectrometry method for the quantification of ATR in rabbit plasma using p‐coumaric acid as an internal standard (IS). Following liquid–liquid extraction, chromatographic separation of the reconstituted samples was achieved isocratically on a Syncronis‐C18 column with a mobile phase consisting of aqueous ammonium acetate (10 mM, pH 4)‐ methanol and acetonitrile mixture (8 : 92, v/v) at a flow rate of 0.6 ml/min. ATR and IS were detected using electrospray ionization operated in negative multiple reaction monitoring mode. The calibration curve was linear (r² ≥ 0.990) over the concentration range of 1–4000 ng/ml with a lower limit of quantitation of 1 ng/ml. The mean extraction recovery of ATR and IS from rabbit plasma was greater than 85%. The method complied well with US Food and Drug Administration guidelines for selectivity, sensitivity, accuracy, precision, matrix effect, dilution integrity, carry‐over effect and stability. The method was successfully applied to in vitro metabolic stability (using rabbit liver microsomes) and in vivo pharmacokinetic study after oral administration of ATR at a dose of 10 mg/kg in New Zealand rabbits. Copyright © 2015 John Wiley & Sons, Ltd.     

Micellar effect of sodium dodecyl sulfate on the reactions between iron(II) and p-benzoquinone, and iron(III) and hydroquinone

The micellar effet of sodium dodecyl sulfate (SDS) on the initial stages of the reaction between (1) Fe(II) and p-benzoquinone, and (2) Fe(III) and hydroquinone have been investigated. In the former case acceleration was observed, the rate-[surfactant] profile showing a maximum. SDS has an inhibitory effect on the latter reaction. Kinetic analysis has been carried out using Berezin's approach.

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() 1) Fe(II) 2) Fe(III) . - . . , .

     

Kinetics of some electron-transfer reactions of iron (III)-2,2′-bipyridyl complex. Micellar effect of sodium dodecyl sulphate

Iron(III)-2,2′-bipyridyl complex obtained, in situ, by direct mixing of iron(III) and 2,2′-bipyridyl, oxidizes aniline, thiourea, and ascorbic acid. The reaction is markedly accelerated by sodium dodecyl sulphate. The rate-[surfactant] profile exhibits a maximum. The kinetic analysis of the micellar effect has been carried out using Berezin's approach. The binding constants of 2,2′-bipyridyl, aniline, thiourea, and ascorbic acid have been determined. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 171–179, 1997.     

Oxidative decarboxylation of arylacetic acids in water: One-pot transition-metal-free synthesis of aldehydes and ketones

One-pot transition-metal-free synthesis of aromatic aldehydes and ketones via oxidative decarboxylation of arylacetic acids in water is developed. Protocol relies on the direct decarboxylation of sp³-hybridized carbon in water without any over oxidation into carboxylic acids with minimal waste. Reaction mechanism is investigated and application of this protocol is demonstrated on a gram scale.     

Continuous Production of Thermostable α-Amylase by Immobilized Bacillus Cells in a Fluidized-Bed Reactor

The exponential cells ofBacillus cereus immobilized in calcium alginate and spun into microcylindrical particles were used in a fluidized-bed reactor for continuous synthesis of thermostable α-amylase. The reactor was operated over a period of 30 d with a dilution rate of 0.33 h^-1, producing 1000–1200 U/mL of enzyme. The productivity of the reactor was in the range of 330–396 kU/h. A 20-fold increase in the productivity with respect to batch fermentation with free cells was attained.     

Cloaks for suppression or enhancement of scattering of diffuse photon density waves

In this paper we investigate the entanglement dynamics between two two-level atoms interacting with two coherent fields in two spatially separated cavities which are filled with a Kerr-like medium. We examine the effect of nonlinear medium on the dynamical properties of entanglement and atomic occupation probabilities in the case of even and odd deformed coherent states. The results show that the deformed fields play important roles in the evolution of entanglement. Also, the results demonstrate that entanglement sudden death, sudden birth and long-distance can be controlled by the deformation and nonlinear parameters.