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A commercially available radioimmunoassay (RIA) kit was used to study the effects of organic solvents on antigen-antibody interactions. The RIA analysis was carried out in aqueous-organic two phase systems. After exposure to hydrophobic organic solvents the antibodies retained full binding capacity, while less hydrophobic solvents caused partial inactivation of the antibodies. A practical analysis
The shape of the profiles of enzyme activity versus water activity for four different lipases were independent of the reaction used to determine the activity. The profile for each lipase (Rhizopus arrhizus, Pseudomonas sp., Candida rugosa and Lipozyme) in esterification, hydrolysis and transesterifications profiles were the same. In transesterification the yield was unaffected by the water activit
Polyacrylamide beads and celite were used for immobilization of bovine α-chymotrypsin and lipase B from Candida antarctica. Polyacrylamides with a high degree of cross-linking afforded high catalytic rates when used as immobilization matrices. Derivatization of the polymer with carboxyl and tertiary amino groups prior to immobilization caused no significant changes in α-chymotrypsin behavior. The
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
Differential scanning calorimetry was the method to investigate the thermostability of chymotrypsin. The transition temperature decreased by approx. 30°C when the dry enzyme became highly hydrated. High degree of hydration corresponded to extensive conformational changes during protein denaturation, reflected by large enthalpy values. Sorbitol, lyophilized together with the enzyme, caused the dest
The thermal inactivation of lyophilized chymotrypsin was studied at controlled water activities. At 60 °C the enzyme showed good stability except at aw 0.97, whereas at 75 °C considerable inactivation occured at most water activities. Increasing the amount of buffer on the preparation decreased the stability significantly. The optimal temperature of enzymatic activity was increased 14 °C, when the
Acyl migration in 2-monoolein dissolved in solvents under conditions common in lipid modification reactions has been studied. The effects on acyl migration of solvent, incubation temperature, water activity, polar additives and solid additives have been investigated. Extensive acyl migration occured in aliphatic hydrocarbons and water-miscible alcohols under dry conditions. The acyl migration rate
Methods used for the regeneration of cofactors in organic media are reviewed. Substrate-driven regeneration methods include the use of a second substrate of the same enzyme and the use of a second enzyme and its substrate. The use of mediators in oxidoreductions is described and examples of photochemical and electrochemical regeneration methods are presented. General problems and possibilities of
Synthesis of partial glycerides in a solvent-free system has been investigated with various acyl donors and glycerol as substrates and a 1,3-specific immobilized lipase to catalyze the reaction. Capric acid was the most efficient acyl donor, compared with ethyl caprate and tricaprin. However, to obtain a high yield of dicaprin and a low amount of tricaprin, ethyl caprate was the acyl donor of choi
α-Chymotrpysin (EC 3.4 21.1) was immobilized by deposition on celite and subsequent cross-linking with glutaraldehyde. The effects of different mixtures of aqueous buffer and acetonitrile on the immobilized preparation were evaluated using a dipeptide synthesis as model reaction. The initial reaction rate at 6-95% of water increased with increasing water content. The maximum yield of peptide had t
A depeptide synthesis was drastically influenced by the reaction temperature, in the range from −30° to 25°C. This article shows the kinetic reasons of this effect. α‐Chymotrypsin was immobilized on celite and used in four different water‐miscible solvents containing small amounts of water‐miscible solvents containing small amounts of water. The reaction studied was the aminolysis of N‐acetyl‐L‐ph
The effect of the addition of sorbitol on the activity and stability of enzymes was examined by monitoring transesterification reactions performed in organic media at various water activities (aw = 0.08 to 0.97). Lipases from Chromobacterium viscosum and Candida rugosa immobilized on celite, and chymotrypsin, free or immobilized on celite, were used. When the sorbitol‐containing enzymes were emplo
A novel total enzymatic synthesis of [Leu]- and [Met]-enkephalin derivatives was accomplished in low-water content systems at a preparative scale. α-Chymotrypsin, papain, thermolysin and bromelain adsorbed on Celite were used as catalysts. Organic solvents such as acetonitrile and ethyl acetate with small amounts of buffer added or at specific water activity were used as reaction media. Simple rea
