Sol-gel-derived prussian blue-silicate amperometric glucose biosensor

A new type of inorganic biosensor is introduced. The sensor comprises glucose oxidase enzymes encapsulated in a sol-gel-derived Prussian blue-silicate hybrid network. Glucose is detected by the biocatalytic reduction of oxygen followed by catalytic reduction of hydrogen peroxide by the Prusian blue catalyst. The sol-gel silicate entails a rigid encapsulating matrix, the Prussian blue provides chemical catalysis and charge mediation from the reduction site to the supporting electrode, and the enzyme is responsible for the biocatalysis. The feasibility of a dual optical/electrochemical mode of analysis is also demonstrated.     

Thermodynamics of the complexing of uranyl ions with 1-phenyl-3-methyl-4-benzoylpyrazolone-5 in aqueous dioxane

The thermodynamics of the complexing between hexavalent U and 1-phenyl-3-methyl-4-benzoylpyrazolone-5 (PMBP) have been studied in 70 vol% aqueous—dioxane medium at 25 and 35±0.1°C following the Bjerrum—Calvin pH titration technique, as applied by Van Uitert and Haas. The ligand is mono-protonic. The refinement of results of formation constants has been accomplished by the method of least squares treatment after an algebraic transformation. The formation of 1:1, 1:2 and 1:3 complexes has been observed, the order of stability being log K₁ > log K₂ > log K₃. The stability invariably increases with an increase in temperature both in aqueous as well as aqueous dioxane media. The changes in ΔG⁰, ΔH⁰ and ΔS⁰ at 25 and 35°C for the overall equilibrium constants have also been evaluated. Uranyl complexes of PMBP are entropy stabilized, the values of enthalpy changes being positive. Other factors which affect chelate stability are briefly discussed.     

A study on the mechanism of failure in keratin

The mechanical behavior of keratin is studied, focusing on the mechanism of failure. For this purpose, a new procedure has been suggested to differentiate the time-dependent and time-independent losses of energy at different strain levels. The matrix of keratin fibers was found to play an important role in the mechanism of failure.     

Stability and reactivity of all-metal aromatic and antiaromatic systems in light of the principles of maximum hardness and minimum polarizability

It is demonstrated that among various possible isomers of all-metal aromatic compounds such as Al(4)(2-) and their complexes the most stable isomer with the minimum energy is the hardest and the least polarizable. A similar situation is observed for different isomers of all-metal antiaromatic compounds such as Al(4)(4-) and their complexes. It is shown that linear Al(4)(4-) is energetically more stable than its cyclic isomer. The reaction energies associated with the complexation processes highlight the stability of those complexes. The difference in energy, hardness, and polarizability between a cyclic molecule and its linear counterpart convincingly shows that an aromatic molecule exhibits negative changes in energy and polarizability but positive changes in hardness as expected from the principles of minimum energy, minimum polarizability, and maximum hardness. Although the aromaticity of Al(4)(2-) is unequivocally established through this study, the antiaromaticity picture in the case of Al(4)(4-) is shown to be poorly understood;however, the present analysis sheds light on this controversy.     

A new chelating resin for preconcentration and determination of Mn(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II) by flame atomic absorption spectrometry

A new polychelatogen, AXAD-16-1,2-diphenylethanolamine, was developed by chemically modifying Amberlite XAD-16 with 1,2-diphenylethanolamine to produce an effective metal-chelating functionality for the preconcentration of Mn(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II) and their determination by flame atomic absorption spectrometry. Various physiochemical parameters that influence the quantitative preconcentration and recovery of metal were optimized by both static and dynamic techniques. The resin showed superior extraction efficiency with high-metal loading capacity values of 0.73, 0.80, 0.77, 0.87, 0.74, and 0.81 mmol/g for Mn(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II), respectively. The system also showed rapid metal-ion extraction and stripping, with complete saturation in the sorbent phase within 15 min for all the metal ions. The optimum condition for effective metal-ion extraction was found to be a neutral pH, which is a great advantage in the preconcentration of trace metal ions from natural water samples without any chemical pretreatment of the sample. The resin also demonstrated exclusive ion selectivity toward targeted metal ions by showing greater resistivity to various complexing species and more common metal ions during analyte concentration, which ultimately led to high preconcentration factors of 700 for Cu(II); 600 for Mn(II), Ni(II), and Zn(II); and 500 for Cd(II) and Pb(II), arising from a larger sample breakthrough volume. The lower limits of metal-ion detection were 7 ng/mL for Mn(II) and Ni(II); 5 ng/mL for Cu(II), Zn(II), and Cd(II), and 10 ng/mL for Pb(II). The developed resin was successful in preconcentrating metal ions from synthetic and real water samples, multivitamin-multimineral tablets, and curry leaves (Murraya koenigii) with relative standard deviations of < or = 3.0% for all analytical measurements, which demonstrated its practical utility.     

Polymerization of styrene with chromium acetylacetonate and triethylaluminum and diethylaluminum bromide

Kinetics of the polymerization of styrene in the presence of benzene at 30°C., with chromium acetylacetonate in combination with triethylaluminum and also in combination with diethylaluminum bromide as catalyst, have been studied. Chromium acetylacetonate forms a homogeneous system with triethylaluminum, and chromium acetylacetonate with diethylaluminum bromide behaves as a heterogeneous system. This homogeneous catalyst system, though reported inactive in the polymerization of α-olefins, has been found effective with styrene. Depending on the homogeneity and heterogeneity of the system, the rate of polymerization is proportional to half order and first order of catalyst concentration. A probable reason for the effect of homogeneity on the order of reaction has been discussed. A study of the effect of diethylzinc as a chain-transfer agent has helped to confirm the mechanism of polymerization.     

Solvent extraction studies of radioisotopic exchange of36Cl with Chloramine-B in strong acid medium

Exchange studies with³⁶Cl and Chloramine-B in strong acid medium revealed that the extent of exchange is less than that occurs at pH 3.3 indicating the formation of a new species of Chloramine-B which is not participating in the exchange reaction and this has been confirmed by conductometric titration of Chloramine-B with dilute solutions of H₂SO₄, HCl, HClO₄ and CH₃COOH.     

Laser Raman spectra of mixed crystals of [(NH4)1−x Kx]2 SO4

The Raman spectra of mixed crystals of [(NH₄)_1?x K _x ]₂ SO₄ in the region 50–3400 cm^?1 at 293 K and below 223 K have been reported. At room temperature 293 K, as the concentration of K⁺ ion increases in the crystal up to 50%, the frequencies of the totally symmetric vibrations of SO ₄ ^2? and NH ₄ ⁺ ions increase and thereafter the frequency of SO ₄ ^2? vibration decreases and attains the value in K₂SO₄. This change in frequency up to 50% of potassium concentration is due to the breaking of hydrogen bonds of the type N-H...O. The behaviour of Raman intensities of A _g (v ₁) mode of SO ₄ ^2? for various concentrations (x=0, 0·03, 0·11, 0·5, 0·85) suggest that the phase transition changes from first order type to one of second order. The phase transition in mixed crystals of [(NH₄)_1?x K _x ]₂ SO₄ can be a cooperative phenomenon arising from a coupling between (NH₄)⁺ ions through hydrogen bonds with the distorted SO ₄ ^2? ions in the low temperature phase.     

Kinetics of growth and catechol production byBacillus stearothermophilus BR321

Applied Biochemistry and Biotechnology - A continuous bioprocess for the specialty chemical catechol has been developed usingBacillus stearothermophilus BR321. Themeta pathway for phenol...