| 1. |
- Wahlgren, Marie C, et al.
(författare)
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Adsorption of globular model proteins to silica and methylated silica surfaces and their elutability by dodecyltrimethylammonium bromide
- 1993
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - 0927-7757. ; 70:2, s. 139-149
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between a cationic surfactant (dodecyltrimethylammonium bromide) and six model proteins adsorbed on to methylated silica and silica surfaces was investigated. The proteins were bovine serum albumin, cytochrome c, β-lactoglobulin, α-lactalbumin, lysozyme and ovalbumin. The adsorption of the proteins at pH 7 and their subsequent removal by surfactant were studied by in situ ellipsometry. The degree of desorption upon dilution and the degree of elutability were compared and no relationship between these parameters could be found, which indicates that the mechanisms behind the two ways of protein removal are quite different. Further, the degree of elutability by surfactant was related to the physicochemical properties of the proteins. It was found that the size, charge, temperature of denaturation and adiabatic compressibility influenced the degree of elutability at the hydrophilic negatively charged silica surfaces for those of the model proteins that were still adsorbed after buffer rinsing. Negatively charged proteins with high denaturation temperatures, indicating high structural stability, did not adsorb on to this surface (ovalbumin) or adsorbed to a very low degree and were desorbed upon rinsing with buffer (β-lactoglobulin). All proteins adsorbed on to the hydrophobic methylated silica and the parameters that seemed to influence the degree of elutability were size and shell hydrophobicity of the proteins.
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| 2. |
- Wahlgren, Marie C, et al.
(författare)
-
Dextran modifications of polysulfone UF-membranes: Streaming potential and BSA fouling characteristics
- 1990
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Ingår i: Acta Polytechnica Scandinavica, Chemical Technology Series. - 1239-0518. ; 194, s. 3-18
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Tidskriftsartikel (refereegranskat)abstract
- Polysulfone ultrafiltration membranes were modified with dextran, dextran sulfate and diethylaminoethyl (DEAE) dextran. The behavior of the modified membranes towards static adsorption of bovine serum albumin (BSA) was investigated in the pH range 3-7. The modified membranes showed lower flux losses after protein adsorption than unmodified membranes. The plain dextran was considered to be the best choice of the three as a modifying agent. Streaming potentials were measured for DEAE dextran and dextran T500 modified membranes as a function of pH. The isoelectric points of the membranes were 5.9 and 4.6, respectively. Titration data for DEAE and dextran T500 are also presented. The modification of membranes with dextrans of different molecular weight average indicated that the shorter dextran molecules (Dextran T10) gave a better result than the larger ones (Dextran T500).
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| 3. |
- Wahlgren, Marie C., et al.
(författare)
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Interaction of Cetyltrimethylammonium Bromide and Sodium Dodecylsulphate with b-lactoglobulin and Lysozyme at Solid Surfaces
- 1991
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Ingår i: Journal of Colloid and Interface Science. - 1095-7103. ; 142:2, s. 503-511
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Tidskriftsartikel (refereegranskat)abstract
- The interaction of two ionic surfactants, CTAB and SDS, with β-lactoglobulin and lysozyme at surfaces was monitored by in situ ellipsometry. The effects of the surfactants on proteins adsorbed at a surface as well as the adsorption from protein/surfactant mixtures were studied. The behavior at four different surfaces, silicon oxide, chromium oxide, nickel oxide, and methylated silica, was investigated. The adsorbed amounts of protein were in all cases below or in the range of what would be expected for monolayer adsorption. The elutability of protein seemed to be most complete at the methylated silica surface while for the oxide surfaces the degree of elution was decreasing in the order silica, chromium oxide, and nickel oxide. The effects of surfactants on adsorbed protein films with no protein present in the solution were described according to four adsorption/displacement models: (1) Removal of the protein upon addition of surfactant. (2) Replacement of the protein by the surfactant. (3) Reversible adsorption of the surfactant to the surface with adsorbed protein. (4) Partial removal of protein according to model 1 or 2. When surfactants were premixed with protein prior to adsorption, the interaction between protein and surfactant in solution had to be taken into account. This was reflected in differences in the amounts adsorbed obtained after adsorption as well as after rinse between these experiments and those where surfactant was added after preadsorption of protein. Under certain conditions the presence of surfactant completely prevented protein adsorption.
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| 4. |
- Wahlgren, Marie C., et al.
(författare)
-
The adsorption from solutions of β-lactoglobulin mixed with lactoferrin or lysozyme onto silica and methylated silica surfaces
- 1993
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797. ; 158:1, s. 46-53
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption from pure protein solutions and binary mixtures of proteins with opposite net charges was studied at pH 7 by in situ ellipsometry. The investigated proteins were β-lactoglobulin, lactoferrin, and lysozyme. On hydrophilic silica surfaces, β-lactoglobulin (negatively net charged) adsorbed in small amounts while lactoferrin and lysozyme (both positively net charged) adsorbed in higher quantities. All the proteins adsorbed readily to the methylated silica surfaces. On both surfaces the amounts of β-lactoglobulin adsorbed were higher and the ones for lactoferrin and lysozyme were lower in a high ionic strength buffer (I = 0.17 M) compared to a buffer with low ionic strength (I = 0.02 M). In mixtures of β-lactoglobulin and lactoferrin the proteins interact leading to high adsorbed amounts on the silica surface and to complete irreversibility with respect to rinsing with buffer. The effect is reduced by increasing the ionic strength of the buffer and by decreasing the overall concentration of proteins in the bulk. This is interpreted in terms of electrostatic interactions between the two proteins. The adsorbed amount from a β-lactoglobulin/lactoferrin mixture to a methylated silica surface is between the amounts for the pure proteins, and the adsorbate is a mixture of lactoferrin and β-lactoglobulin as indicated by measurements with radioactively labeled lactoferrin. An interesting observation was that the adsorbed amount from a β-lactoglobulin/lactoferrin mixture onto a methylated silica surface increased upon rinsing at high bulk concentrations and at low ionic strength. The adsorption from mixtures of β-lactoglobulin and lysozyme is also strongly influenced by electrostatic interactions. At low ionic strength a bulk precipitation takes place, which probably is the reason for the very high amounts adsorbed onto both surfaces examined. This effect is only partially reduced at higher ionic strength.
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| 5. |
- Wahlgren, Marie C, et al.
(författare)
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The concentration dependence of adsorption from a mixture of β-lactoglobulin and sodium dodecyl sulfate onto methylated silica surfaces
- 1992
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797. ; 148:1, s. 201-206
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption from a mixture of SDS and β-Lactoglobulin, 1:5 (), onto a methylated silica surface was studied in situ by ellipsometry. The amounts adsorbed from different concentrations of the mixture, at pH 7, were compared with those adsorbed from the corresponding pure SDS and β-lactoglobulin solutions. At high concentrations of the mixture, where the CMC of SDS is approached or exceeded, the adsorbate was probably dominated by SDS, indicated by similar kinetics and amounts adsorbed as for SDS solution alone. The amount adsorbed increased, in this concentration range, when the system was rinsed with buffer solution. This was probably due to an exchange between SDS and β-lactoglobulin when the system was diluted. At intermediate concentrations of SDS and β-lactoglobulin, the amounts adsorbed from the mixtures increased and reached a maximum. This maximum was observed both before and after rinsing. Before rinsing the adsorbate might have been a mixture of SDS and β-lactoglobulin while after rinsing probably only β-lactoglobulin remained. At low concentrations, larger amounts were adsorbed from the mixture than from β-lactoglobulin solution alone. In this concentration range rinsing caused minor desorption, indicating that SDS is co-adsorbed with the protein, even in those cases were no adsorption from a pure SDS solution was seen. This indicated that the binding of SDS to β-lactoglobulin at low concentrations is stronger than to the silica surface and that this binding facilitated the adsorption of protein.
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