Intermolecular interactions in newly spread serum albumin monolayers

Blank, Martin

doi:10.1016/0021-9797(69)90187-8

Cited by 20 publications

(1 citation statement)

References 13 publications

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“…Complete unfolding of the enzyme molecules may require long contact times [8,23], implying that a range of unfolded enzyme conformations can be present at the interface at any time. Lateral interactions between partially unfolded enzyme molecules adsorbed at interfaces may occur [24] and depend on surface coverage and extent of unfolding of the enzyme molecules. The extent of unfolding itself has been shown to decrease with increasing surface coverage [8,11,25].…”

Section: Interfacial Inactivation In the Stirred-cell Contactormentioning

confidence: 99%

Interfacial inactivation of epoxide hydrolase in a two-liquid-phase system

Baldascini

Janssen

2005

Enzyme and Microbial Technology

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Enantioselective epoxide hydrolases are useful biocatalysts for the preparation of enantiopure epoxides and diols. The kinetic resolution of racemic epoxides can be carried out in an organic/aqueous biphasic system to allow use of high epoxide concentrations. Enzyme inactivation in such a system, however, may occur by contact with the interface. In this study, we investigated the factors which influence the interfacial inactivation of Agrobacterium radiobacter epoxide hydrolase in an octane/water biphasic system. Rates of interfacial inactivation were measured both in a stirred-cell, which has a planar interface, and in an emulsion reactor. Interfacial inactivation rates measured in the stirredcell at a fixed interfacial area increased with mixing intensity. Interfacial inactivation rates per unit area were lower in the emulsion reactor than in the stirred-cell and increased with bulk aqueous enzyme concentration. Circular dichroism measurements showed that during biphasic incubation all unadsorbed soluble enzyme existed in the native conformation. Activity assays showed that the dissolved enzyme was also fully active, indicating that inactivated enzyme precipitated from solution. Using an inactive epoxide hydrolase mutant structurally similar to the wild-type enzyme in order to avoid the conversion of the epoxide, it was found that high concentrations of epoxide in the organic phase increased the rate of interfacial inactivation.

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Section: Interfacial Inactivation In the Stirred-cell Contactormentioning

confidence: 99%

Interfacial inactivation of epoxide hydrolase in a two-liquid-phase system

Baldascini

Janssen

2005

Enzyme and Microbial Technology

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The kinetics and mechanism of shear inactivation of lipase from Candida cylindracea

Lee

Choo

1989

Biotech & Bioengineering

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Shearing experiments were conducted in a stirred tank reactor with 0.1% lipase solutions of Candida cylindracea. Inactivation of the lipase solutions were observed at various shear rates from 50 to 150 s(-1) after continuous shearing for ca. 30-240 min under optimal pH and temperature conditions. However, there was no shear stress denaturation of the lipase when it was subjected to shear stresses of 0.72-109.2 kg/m/s(2) and shear rate of 100 s(-1). In the presence of polypropylene glycol, the rate of denaturation of the lipase decreased by 93%. When the lipase solution was filled to the brim, the rate of denaturation of the lipase decreased by 97% compared to that when reactor was half-filled. The rate of denaturation of the lipase decreased by 61% when probes in the fermentor were removed. There was no significant difference in the rate of denaturation of the lipase under ambient conditions compared with that in the absence of oxygen, or in the absence of free metal ions. Recovery of lipase activity from the first hour of shearing was observed at a shear rate of 150 s(-1). The native lipase and the lipase which had recovered its activity showed similar pH profiles, temperature profiles, and activation energies. Temperature was found to have no effect in the rate of shear-induced denaturation of the lipase in the range 20 to 30 degrees C during shearing at 100 s (-1)and optimal pH. Above 30 degrees C, the rate of denaturation of the lipase increased drastically as a function of temperature. The significance of the findings in the de sign of reactor systems for hydrolysis or esterification of oils by lipase will be discussed.

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