| 1. |
- Jha, BK, et al.
(författare)
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A titration calorimetry study of a technical grade APG
- 1998
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 110, s. 230-234
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports titration microcalorimetric measurements on micellization of a technical grade alkyl polyglucoside (APG) surfactant. The dilution enthalpy was recorded at three different temperatures and the curves obtained were compared with those of pure B-octyl glucoside. For comparative purposes titration microcalorimetry was also conducted with the conventional nonionic surfactant octa(ethylene glycol)monododecyl ether and with the anionic surfactant sodium dodecylsulfate, SDS. The results indicate that, contrary to the alcohol ethoxylate, both glucoside surfactants undergo micellization without much loss of water of hydration. Compared with the pure octyl glucoside, the technical grade APG exhibited a lower cmc and a less endothermic enthalpy of micellization at room temperature.
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| 2. |
- Jha, BK, et al.
(författare)
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Titration microcalorimetry studies of the interaction between humicola lanuginosa lipase and ionic surfactants
- 1999
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 213, s. 262-264
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Tidskriftsartikel (refereegranskat)abstract
- Microcalorimetry has been used to study the interaction between Humicola lanuginosa lipase and either the anionic surfactant sodium dodecyl sulfate, SDS, or the cationic surfactant tetradecyltrimethylammonium bromide, TTAB. For SDS no conclusive evidence was obtained of whether or not an enzyme-surfactant complex is formed. Although not unambiguous, the calorimetric titration curves obtained with TTAB indicate formation of such a complex.
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| 3. |
- Lee, L-T, et al.
(författare)
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Lipase-surfactant interactions studied by neutron reflectivity and ellipsometry
- 1999
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Ingår i: Journal of Physical Chemistry B. - 1520-6106 .- 1520-5207. ; 103, s. 7489-7494
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between a microbial lipase and an anionic and a cationic surfactant at the air-water interface has been studied by neutron reflectivity. Sodium dodecyl sulfate (SDS) and tetradecyltrimethylammonium bromide (TTAB) were used as anionic and cationic surfactant, respectively. The same enzyme-surfactant systems were also studied at the interface between a hydrophobic solid surface and water by ellipsometry, and the results from the two techniques were compared. Surface tension measurements were also performed in order to monitor complex formation in bulk. The data obtained from neutron reflectivity and from ellipsometry were in very good agreement with each other. Both techniques show that lipase adsorbs readily at the interfaces and that SDS at low concentration does not interact strongly with this protein layer. At higher SDS concentration, the protein is displaced from the surface. On the other hand, when TTAB is added at low concentration, a thick lipase-surfactant layer is formed at the surfaces. This compact layer is solubilized by further addition of the cationic surfactant.
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| 4. |
- Skagerlind, P, et al.
(författare)
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Lipase-surfactant interactions
- 1998
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Ingår i: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 108, s. 47-57
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Tidskriftsartikel (refereegranskat)abstract
- Interactions between different amphiphiles and Rhizomucor miehei lipase were investigated by a variety of techniques. Complex formation in aqueous bulk solution was studied using surface tension measurements. Interactions at the oil-water and the solid-water interfaces were investigated by measuring mobility of emulsion droplets and by ellipsometry, respectively. The results from the different methods were coherent and indicated that cationic surfactants form complex with the lipase over a broad pH range, also below the isoelectric point of the lipase. No such interaction were found for neither anionic or nonionic surfactants. It is postulated that the interaction between cationic surfactants and lipase is due to a combination of electrostatic attraction and hydrohobic interaction and that no such combined interaction occurs with anionic surfactants. The interaction between cationic surfactant and lipase leads to a reduction of reaction rate in lipase-catalyzed hydrolysis of a palm oil. It is also shown that in the same model reaction a normal straight chain alcohol ethoxylate is a substrate for the lipase. An appreciable amount of fatty acid ester of the surfactant is formed as biproduct of the reaction. Branched-tail alcohol ethoxylates are not substrates and appear not to be competitive inhibitors for the enzyme. Likewise, the double-tailed ester surfactant sodium bis(2-ethylexyl)sulfosuccinate (AOT) seems not to interact with the enzyme active site. Thus, anionic and nonionic surfactants with bulky hydrophobic tails are the preferred surfactants for microemulsion-based reactions with Rhizomucor miehei lipase as catalyst.
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