Direct thin-layer densitometric determination of citric acid in fermentation media

Summary A new method for determining citric acid in fermentation media is proposed. The procedure involves direct application of properly diluted culture medium filtrate to a TLC plate, subsequent chromatographic separation and coloration of citric acid spots, and densitometric evaluation. By this method, citric acid can be determined with a good accuracy in the range from 1–5 g/l. The densitometric analysis proved to be of high reproducibility with a relative standard deviation from 2–4% and a 99.7% recovery efficiency for citric acid added to the culture medium.

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Direkte Dünnschicht-densitometrische Bestimmung der Citronensäure in Fermentationsflüssigkeiten

Zusammenfassung Eine neue Methode zur Bestimmung der Citronensäure in Fermentationsflüssigkeiten umfaßt den direkten Auftrag des geeignet verdünnten Kulturfiltrats auf die Dünnschichtplatte, chromatographische Trennung, Anfärbung der Citronensäureflekken und densitometrische Auswertung. Die Citronensäure kann im Konzentrationsbereich von 1–5 g/l mit guter Genauigkeit nachgewiesen werden. Die relative Standardabweichung beträgt 2–4%. Im Durchschnitt wurden 99,7 % der der Fermentationsflüssigkeit zugesetzten Citronensäure wiedergefunden.

     

Lewis acid mediated functionalization of β-lactams: mechanistic study and synthesis of C-3 unsymmetrically disubstituted azetidin-2-ones

A convenient and efficient route to novel unsymmetrically disubstituted azetidin-2-ones is described. β-Lactam carbocation equivalents of type 1 and active aromatic substrates in the presence of a Lewis acid promote a facile and stereoselective C-3 substitution to provide monosubstituted β-lactams (3,4) and symmetrically disubstituted β-lactams (5). cis-3-(4′-Methoxyphenyl)-3-phenylthioazetidin-2-ones (4) undergo further substitution with active aromatic substrates mediated by a Lewis acid to afford unsymmetrically disubstituted azetidin-2-ones (7).     

Alpha:2n:alpha molecular band in 10Be

The 10.15 MeV resonance in 10Be has been probed via resonant 6He+4He elastic scattering. It is demonstrated that it is the Jpi=4+ member of a rotational band built on the 6.18 MeV 0+ state. A Gammaalpha of 0.10-0.13 MeV and Gammaalpha/Gamma=0.35-0.46 were deduced. The corresponding reduced alpha width, gamma2alpha, indicates one of the largest alpha-cluster spectroscopic factors known. The deformation of the band, including the 7.54 MeV, 2+ member, is large (h2/2I=200 keV). Such a deformation and the significant degree of clusterization signals a well-developed alpha:2n:alpha molecular structure.     

Dust ion‐acoustic solitons with trapped q‐non‐extensive electrons,dissipative processes,and streaming ions

The characteristics of dust ion‐acoustic waves (DIAWs) that are excited because of streaming ions and hot q‐non‐extensive electrons obeying a vortex‐like distribution are investigated. By exploiting a pseudo‐potential technique, we have derived an energy integral equation. The presence of non‐extensive q‐distributed hot trapped electrons and a streaming ion beam has been shown to influence soliton structure quite significantly. The evolution of the soliton‐like perturbations in complex plasmas, taking into account the dissipation processes, are also investigated, obtained by numerically solving the modified Schamel, equation whose widths are dependant on electron trapping efficiency β. Our illustrations indicate that compressive DIAWs develop in this plasma. As the plasmas in reality have a relative flow, such an analysis can be used to understand the DIA solitary structures observed in the mesospheric noctilucent clouds.     

Chromatographic analysis of alkylresorcinols and their metabolites

Alkylresorcinols (AR) are phenolic lipids present in high amounts in the bran fraction of wheat and rye. AR are of scientific interest as bioactive compounds, as markers for the presence of wholegrain or bran fractions of wheat and rye in food products, and as possible biomarkers of intake for wholegrain wheat and rye. This review discusses their extraction from cereal grains, food and biological fluids, and the various chromatographic methods used in their analysis.     

Reactions induced by 35 MeV 6He beam on 12C and 14C

The ⁶He+^12,14C scattering and reactions have been studied using a 35 MeV ⁶He radioactive beam and preliminary results are presented. The three-body reaction ⁶He+¹²C ↦ ¹⁰Be+2 α has been clearly identified and sequential decay of intermediate states in ¹⁴C has been studied. Search for an analog reaction on ¹⁴C, ⁶He+¹⁴C ↦ ¹²Be+2 α, has not given conclusive results yet. Other interesting reactions with this entrance channel are discussed.     

Spectrophotometric determination of morphine

Morphine reacts with potassium iodate in an alkaline medium to give a yellowish golden color having maximum absorbance at 450 nm. The reaction is specific for morphine, having 2 μg/ml as minimum limit of identification, and provides a basis for a new spectrophotometric determination of pure morphine in urine, in the presence of codeine and other drugs. The maximum tolerable limits of other drugs are reported.     

Single-nucleotide polymorphism analysis by allele-specific extension of fluorescently labeled nucleotides in a microfluidic flow-through device

We describe a microfluidic approach for allele-specific extension of fluorescently labeled nucleotides for scoring of single-nucleotide polymorphism (SNP). The method takes advantage of the fact that the reaction kinetics differs between matched and mismatched configurations of allele-specific primers hybridized to DNA template. A microfluidic flow-through device for biochemical reactions on beads was used to take advantage of the reaction kinetics to increase the sequence specificity of the DNA polymerase, discriminating mismatched configurations from matched. The volume of the reaction chamber was 12.5 nL. All three possible variants of an SNP site at codon 72 of the p53 gene were scored using our approach. This work demonstrates the possibility of scoring SNP by allele-specific extension of fluorescently labeled nucleotides in a microfluidic flow-through device. The sensitive detection system and easy microfabrication of the microfluidic device enable further miniaturization and production of an array format of microfluidic devices for high-throughput SNP analysis.     

Separation and identification of steroids produced by fermentative oxidation of progesterone

Summary A simple method is described for the separation and identification of steroids produced during the fermentative oxidation of progesterone by Fusarium spp. The steroid products are separated by thin-layer chromatography on silica-gel G with ethylacetate-cyclohexane (21) as solvent and characterized by colour reaction with 50% sulphuric acid and UV fluorescence. The entire procedure can be completed within one hour and thus could be useful in the control of biological oxidation of progesterone.

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Zusammenfassung Eine einfache Methode wird beschrieben zur Trennung und Identifizierung von Steroiden, die durch fermentative Oxydation von Progesteron mit Fusarien gewonnen wurden. Die Steroide werden durch Dünnschicht-Chromatographie auf Silicagel G mit Äthylacetat-Cyclohexan (21) getrennt und mit Hilfe der Farbreaktion mit 50% iger Schwefelsäure und UV-Fluorescenz identifiziert. Das Verfahren kann in 1 h ausgeführt und bei der Kontrolle der biologischen Oxydation von Progesteron angewendet werden.