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Temperature effects on protease catalyzed acyl transfer reactions in organic media

The influence of reaction temperature on synthesis activity, product yield and nucleophile specificity for α-chymotrypsin and subtilisin Carlsberg were studied. The enzymes were immobilized on Celite and used in acetonitrile with a water content of 10%. Acyl-transfer reactions with Ac-PheOEt as acyl donor and 11 different amino acid amides and 3 dipeptides as nucleophiles were studied. The decreas

On the importance of the support material for bioorganic synthesis : Influence of water partition between solvent, enzyme and solid support in water‐poor reaction media

α‐Chymotrypsin was adsorbed on solid support materials and the catalytic activity of the preparations in organic solvents was studied. The activity was highly dependent on the nature of the support material and on the amount of water present in the reaction mixture. There appears to be competition for the water in the system between the enzyme, the support material and the solvent. The support mat

Oxygen supply to immobilized cells - 3. Oxygen supply by hemoglobin or emulsions of perfluorochemicals

Oxygen supply is a critical point in technical processes when aerobic cells are used in immobilized preparations. This report concerns the use of hemoglobin or emulsions of perfluorochemicals (completely fluorinated organic compounds) to carry oxygen to immobilized cells. Both methods work well and do not seem to harm the cells. The perfluorochemical method of improving oxygen supply showed a high

Aspects of biocatalyst stability in organic solvents

The stability of biocatalysis in systems containing organic solvents is reviewed. Among the examples presented are homogeneous mixtures of water and water-miscible organic solvents, aqueous/organic two-phase systems, solid biocatalysts suspended in organic solvents, enzymes in reverse micelles and modified enzymes soluble in water immiscible solvents. The stability of biocatalysts in organic solve

Validation of a dietary record routine in geriatric patients using doubly labelled water

Objective: To validate a 7-day estimated dietary record routine with standardized portion sizes and household measuring in a clinical setting with the doubly labelled water (DLW) method as the reference method. Design: Energy expenditure was measured with deuterium (2H) and oxygen-18 (18O), and water loss was estimated by 2H dilution as part of the DLW measurements. Energy and water intake was mea

Technique for testing the patency of laser iridotomies

With laser iridotomy it may often be difficult to achieve total penetration of the iris, particularly in very light or very dark irides. It may be impossible to determine with the slit-lamp whether a small laser iridotomy is functionally penetrating. We describe a straightforward method to test iridotomies for aqueous flow patency. Transcorneally introduced fluorescein is used to delineate any aqu

Characterization of Gluconobacter oxydans immobilized in calcium alginate

Gluconobacter oxydans cells were immobilized in calcium alginate and the preparation was used for the oxidation of glycerol to dihydroxyacetone. The characterization was done according to the guidelines given by the Working Party on Immobilized Biocatalysts of the European Federation of Biotechnology. The pH optimum of the preparation was found to be 5.0 and the temperature optimum was 40°C. Howev

Substrate specificity of α-chymotrypsin-catalyzed esterification in organic media

11 amino acid derivatives were tested as α-chymotrypsin substrates in the esterification reaction with methanol in organic media. The reactions were carried out in water-saturated ethyl acetate and in acetonitrile containing 4% water. α-Chymotrypsin adsorbed on Celite was used as a catalyst. From initial reaction rate measurements, the Michaelis-Menten parameters Vmax and KM were determine. All th

Oxygen supply to immobilized cells : 5. Theoretical calculations and experimental data for the oxidation of glycerol by immobilized Gluconobacter oxydans cells with oxygen or p‐benzoquinone as electron acceptor

Theoretical calculations of reaction kinetics were done for one‐step reactions catalyzed by cells immobilized in spherical beads. The reactions catalyzed by free cells were assumed to obey Michaelis–Menten kinetics for a one‐substrate reaction. Both external (outside the beads) and internal (inside the beads) mass transfer of the substrate were considered for the immobilized preparations. The theo

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In the present article, the legal nature of representative offices of the international organizations in the territory of member states is opened. In the article, the international-legal status, including immunities and the privilege of representative offices of the international organizations in the territory of member states are open. In this direction, a number of shortcomings of the Vienna con