Flow-injection amperometric determination of oxalate with immobilized oxalate oxidase

Oxalate is immobilized on controlled-pore glass and is used on-line in a glass minicolumn (2.5×25 mm). The hydrogen peroxide formed is detected amperometrically. Oxalate (6×10^?6?9×10^?4 M) is determined in a flowing stream of pH 3.5 citrate (or succinate) buffer. As little as 20 ng (in 40 μl; 5.7×10^?6 M) of oxalate can be detected. Copper inhibition can be removed either by adding EDTA to the carrier stream or incorporating a chelating-resin minicolumn into the flow system prior to the enzyme column.     

Zn2+-dependent peptide nucleic acids probes

Binding of bis-picolylamine-naphthalene diimide-peptide nucleic acid conjugates to complementary DNA is strongly dependent upon Zn2+; ultimately, hybridization is switched ON in the presence muM Zn2+.     

Flow-injection determination of sulphite and assay of sulphite oxidase

Sulphite (1–80 × 10^?5 M) in formaldehyde-stabilized solutions is determined by injection into a flowing stream of pH 8.5 phosphate buffer, passing through a mini-column of sulphite oxidase immobilized on controlled-pore glass, with amperometric detection of the hydrogen peroxide produced. Sulphite oxidase (5–100 U l^?) is determined by injection into a flowing stream of formaldehyde-stabilized 2 × 10^?3 M sodium sulphite in pH 8.0 phosphate buffer; hydrogen peroxide is again monitored.     

Synthesis and characterisation of a series of alkylmagnesium amide and related oxygen-contaminated "alkoxy" compounds

Synthesised either by an unusual tert-butyl metathesis between tert-butyllithium and a n,s-butylmagnesium amide or by reaction of an alkyl Grignard reagent and a sodium amide, five tert-butylmagnesium amides, Bu(t)MgDBA (5)(DBA=dibenzylamide), Bu(t)MgDA (6)(DA=diisopropylamide), Bu(t)MgHMDS (7)(HMDS=1,1,1,3,3,3-hexamethyldisilazide), Bu(t)MgTMP (8)(TMP=2,2,6,6-tetramethylpiperidide) and Bu(t)MgNCy2 (9)(cy=cyclohexyl) have been isolated as crystalline solids. All five amides have been characterised by X-ray crystallography and solution NMR spectroscopic studies. The former studies reveal a common dimeric molecular structure with amido bridges in a planar (MgN)2 ring and terminal Bu(t) ligands on the Mg atoms. Also described is the dodecameric primary amide [Bu(n)MgN(H)Dipp]12 (10a) and its monomeric solvate Bu(n)MgN(H)Dipp.TMEDA (10b)(Dipp=2,6-diisopropylphenyl; TMEDA=N,N,N',N'-tetramethylethylenediamine). The crystal structures of the oxo-insertion products Bu(t)MgOBu(t).THF (11), Bu(t)Mg(mu-OBu(t))(mu-TMP)MgTMP (12) and Mg(OBu(n))HMDS.solv [solv=THF (13a) or Et2O (13b)], made fortuitously during the course of this work, are also presented.     

Some past achievements and future perspectives in main group chemistry

A survey of some recent developments and past achievements in low-valent main group chemistry is presented. Some emerging implications of this area of chemistry in materials science, catalysis and new reagent development are also discussed.     

Notiz über Li2PdO2

Note on Li₂PdO₂ For the first time we prepared ruby-red single crystals of Li₂PdO₂ by reaction with the wall 3 Na₂O + Li₂O₂ + ?Tb₄O₇”?(+ Pd) = 3 Na₂TbO₃ + Li₂PdO₂ + ?TbO₂”?, Pd-tube, 1100°C, 7 d. Single crystal data confirm the Li₂CuO₂-type of structure [a = 375.34(5), b = 298.18(4), c = 931.58(10) pm; spacegroup Immm; d_x = 4.85 g · cm^?3; 144 I₀(hkl); R = 3.54%, Rw = 3.19%; MoKα ; four-circle diffractometer Philips PW 1100] and reveal clearly different parameters compared with those deduced by powder data. The Madelung Part of Lattice Energy, MAPLE, corresponds now to the sum of the MAPLE values of the binary oxides.     

Cyclization of alpha-Oxo-oximes to 2-substituted benzoxazoles

Reactions of oximes 9, 17, and 19 with electrophiles 15a-f and 24 in the presence of anhydrous potassium carbonate or triethylamine give 2-substituted condensed ring oxazoles 10, 16a-c, 18a-d, 20a-c, and 25 in a new general route to these compounds.     

Pulse radiolysis and fourier transform infrared study of neopentyl peroxy radicals in the gas phase at 297 K

The ultraviolet absorption spectrum of the neopentyl peroxy radical (CH₃)₃CCH₂O₂, and the kinetics and products of its self reaction have been studied in the gas phase at 298 K. Absorption cross sections were quantified over the wavelength range 230–290 nm. The measured cross section at 250 nm was; Errors represent statistical (2σ) together with our estimate of potential systematic errors(15%). The kinetics of the decay of the UV absorption following the generation of the neopentyl peroxy radicals was complicated by the rapid decomposition of the (CH₃)₃CCH₂O radicals formed in channel (4a). By measuring the yield of t-butyl peroxy radicals, the branching ratio k_4a/(k_4a + k_4b) was determined to be 0.39 ± 0.03. The rate constant for the self reaction of neopentyl peroxy radicals was k₄ = (1.07 ± 0.22) × 10^?12 cm³ molecule^?1 s^?1. Quoted errors represent 2σ. These results are discussed with respect to the available literature data. © John Wiley & Sons, Inc.     

Stoffwechselprodukte von Mikroorganismen. 177. Mitteilung. Avilamycin C

From cultures of the Avilamycin (Avilamycin A) producing organism, Streptomyces viridochromogenes, strain ETH 23575, a second antibiotic, Avilamycin C, C₆₁H₉₀Cl₂O₃₂ could be isolated in crystalline form. Both Avilamycins belong to the group of the Orthosomycins. By IR., ¹H- and ¹³C-NMR. spectroscopy and by transformation to a common derivative it could be proven that Avilamycin A is a methyl ketone, Avilamycin C the corresponding methyl carbinol.     

Marine adhesives. IV: Hexosamine content of Balanus eburneus adhesive

The adhesive secreted by the barnacle, Balanus eburneus, has been demonstrated to contain two hexosamines, glucosamine and galactosamine. Degradation of the hexosamines during hydrolysis of the adhesive appears to be the reason why previous studies of the adhesive have indicated the absence of hexosamines, or the presence of only one hexosamine.