Pure Organic Phase Phenol Biosensor Based on Tyrosinase Entrapped in a Vapor Deposited Titania Sol‐Gel Membrane

A novel amperometric biosensor was constructed for the determination of phenols in pure organic phase. This biosensor was fabricated by immobilizing tyrosinase in a titania sol‐gel membrane which was obtained with a vapor deposition method. This method was facile and avoided the calcination step needed in conventional titania sol‐gel process. The titania sol‐gel membrane could effectively retain the essential water layer around the enzyme molecule needed for maintaining its activity in organic phase. The experimental parameters such as solvent and operating potential were optimized. At ?100 mV this biosensor showed a good amperometric response to phenols in pure chloroform without any mediator and rehydration of the enzyme. For catechol determination the sensor exhibited a fast response of less than 5 seconds. The sensitivity of different phenols was as follows: catechol > phenol > p‐cresol. Additionally, the apparent Michaelis‐Menten constants of the encapsulated tyrosinase to catechol, phenol and p‐cresol were found to be 0.15±0.003, 0.17±0.008 and 0.21±0.004 mM, respectively. The biosensor had also good reproducibility and stability. This work provided a promising platform for the construction of pure organic phase biosensors and the determination of substrates with poor water solubility.     

Chemischer Transport und Sublimationsverhalten von CrBr3 — Experimente und Modellrechnungen

On the Chemical Transport and Sublimation of CrBr₃ — Experiments and Model Calculations The migration of CrBr₃ in the presence of high concentrations of bromine (for example D(Br₂) = 0,05 mmol/ml; closed silica ampoules) in the investigated temperature range (T? = 625°C to 875°C; T? = 50°C) is a result from the endothermic reaction The chemical transport of CrBr₃ is superimposed with the sublimation. With low concentrations of D(Br₂) and high temperatures T? is the sublimation decisive participated. This is a result of the homogenous equilibrium between CrBr_3,g and CrBr_4,g (2a) The reaction (2a) in comparison with the chemical transport of CrCl₃ with Cl₂ (Gl. (2b)) is more shifted to CrBr_3,g.     

Effect of aryl ligands on the chemical hardness of arylmercury cations

¹⁹F NMR spectroscopy was used to study the exchange reactions involving 4-fluorothiophenoxides, 4-nitrophenoxides, chlorides, and acetates of arylmercury and triphenylphosphinegold. The analysis of the data on equilibrium constants allows one to obtain information on the comparative chemical hardness of ArHg⁺ and Ph₃PAu⁺ cations. The increase in the electron-donating ability of aryl ligands enhances the chemical hardness of ArHg⁺ cations, their influence being best described by ⁰ constants of substituted phenyl groups.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1255–1260, May, 1996.     

Formation of Ad-Layers and Clusters on Condensation of Metal Vapors on Solid Surfaces

Synthesis of organometallic materials can be accomplished in many cases by cocondensation of metal atoms and organic molecules at low temperatures. The reaction kinetics is determined by the competition between metal cluster growth and formation of the organometallic compound. Interesting compounds may contain one or more metal atoms; the latter type could be obtained by reaction between a cluster containing the desired number of metal atoms and an organic molecule. A precise knowledge of the events occurring on condensation of metal atoms and cluster formation can therefore be of value in the control of chemical synthesis. These phenomena have been investigated in connection with the study of the growth of thin metallic films, both experimentally and theoretically. Direct observation of the formation of very small clusters is difficult. The good agreement between experimental results and recent calculations for the development of large clusters, however, allows reliable theoretical conclusions for the first stages of adsorption and cluster formation. The present contribution describes experimental work on film growth and relevant theoretical concepts, and an attempt is made to develop applications to organometallic synthesis.     

Correlations of13C chemical shifts and geometry modifications

The effect of geometry modifications of¹³C chemical shifts has been investigated in a small subset of molecules using both LO-INDO and Gaussian 70 (4–31) calculations. The Gaussian calculations, while known to give poor absolute shifts, compare well to the reparameterized semi-empirical INDO determinations in calculated shift changes. In virtually all cases the signs of the shift changes were found to be opposite to that of the changes in the calculated electronic energy.     

Glass capillary gas chromatography of amino acid enantiomers

Glass capillaries coated with Chirasil-Val, a chirally functionalised polysiloxane, are capable in principle of resolving all protein amino-acid enantiomers in a single run and within a short analysis time, thus allowing for example the quantitative amino acid determination by enantiomer labelling. The elution characteristics of the individual amino acids however are also dependent upon the chemical nature of the capillary wall surface, and a surface pretreatment is found to be necessary if all protein amino acids are to be analysed. Of the various methods of pretreatment tested, etching of borosilicate glass with gaseous HCl followed by deposition of colloidal silicic acid is considered to be the most suitable.     

Zum chemischen Transport von SiAs mit Iod — Experimente und Modellrechnungen

On the Chemical Transport of SiAs using Iodine — Experiments and Thermochemical Calculations Using iodine as transport agent siliconarsenide migrates in a temperature gradient. The direction of the migration depends on the chosen temperature and the concentration of the transport agent. The transport rates were measured for various transport agent concentrations (0.0002 ? C(I₂) ≥ 0,02 mmol/cm³) and for various mean transport temperatures (650 ? T? ? 1 000°C). For low temperatures (e.g. T₁ = 750°C→T₂ = 850°C), low iodine concentrations (e.g. C(I₂) = 0.001 mmol/cm³) and in the presence of H₂O (from wall of silica ampoule) the following exothermic reaction is responsible for the deposition of SiAs-crystals in the sink region:

• SiAs_s + 4HI_g = SiI_4,g + 2H_2,g + 1/4As_4,g

In case of higher temperatures (e.g. T₂ = 1 050°C→T₁ = 950°C) and higher iodine concentrations (e.g. C(I₂) = 0.02 mmol/cm³) SiI_4,g is the transport agent. According to model calculations the following endothermic reaction is responsible for the migration of SiAs to the region of the lower temperature:

• SiAs_s + SiI_4,g = 2SiI_2,g + 1/4As_4,g

The heterogeneous and homogenous equilibria will be discussed and an explanation of the non equilibrium transport behaviour of SiAs is given. Thermochemical data of SiAs are characterized by the quartzmembrane zero manometer technique and further verified by model calculations.     

103Rh-NMR-spektroskopischer Nachweis der gemischten Nonahalogenodirhodate(III), [Rh2ClnBr9–n]3−, n = 0–9

¹⁰³Rh NMR Spectroscopic Evidence of Mixed Nonahalogenodirhodates(III), [Rh₂Cl_nBr_9–n]^3?, n = 0–9 On heating a mixture of the tetrabutylammonium salts (TBA)₃[Rh₂Cl₉] and (TBA)₃[Rh₂Br₉] at 60°C in propylenecarbonate the complete system of the mixed nonahalogenodirhodates(III) [Rh₂Cl_nBr_9–n]^3?, n = 0–9 is formed. In the ¹⁰³Rh nmr spectra 40 different species have been detected, 16 with two equivalent ¹⁰³Rh atoms each resulting in one singlet and 24 with inequivalent ¹⁰³Rh atoms each pair giving two resonances. The signals of the geometric isomeres are not resolved. All 64 expected resonances are really observed. By additional measuring of the ¹⁰³Rh nmr spectra of the fractions n = 0–4 separable by ion exchange chromatography on DEAE cellulose, and utilizing characteristic increments of chemical shifts the complete and unambiguous assignment of all signals is achieved.     

Isolated square planar metal complexes of carbon

Based on the group theory analysis and quantum chemical calculations within the framework of SW X _α method (in relativistic approximation for core electrons and non-relativistic for valence ones), the existence possibility of square planar complexes [M₄C] and [M₄C]^2? (M = Al, Ga, In, Tl, Sc, and Y) in gas phase has been shown. The extraction of Kt₂[M₄C] square planar complexes of carbon in the crystal state is possible too. A high stability of these complexes, in comparison with usual tetrahedral, is achieved due to the formation of five-and four-center bonds (bonds M-M and M-C).     

Combined application of 2D NMR correlation methods and ab initio chemical shift calculations to the structure determination of new heterocyclic compounds

The combined use of 2D NMR correlation methods and ab initio chemical shift calculations is efficient and, in some cases, virtually the only way to determine the structures of new organic compounds. This approach enabled us to establish the structure of the major unusual product of the three-component reaction of imidazo[1,5-a]quinoxalin-4-one, bis(2-chloroethyl)amine hydrochloride, and potassium carbonate in DMF. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2172–2179, December, 2006. Dedicated to Professor A. V. Il’yasov on the occasion of his 70th birthday.