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| 3. |
- Billsten, P, et al.
(författare)
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Adsorption of human carbonic anhydrase II onto silicon oxides surfaces : The effects of truncation in the N-terminal region
- 1998
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Ingår i: The Colloid Science of Lipids New Paradigms for Self-Assembly in Science and Technology. - 1435-1536 .- 0340-255X. - 9783798511125 - 9783798516557 ; 108, s. 161-165
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Konferensbidrag (refereegranskat)abstract
- The adsorption of human carbonic anhydrase II pseudo-wild type (HCAIIpwt) and an N-terminally truncated version thereof onto silica surfaces were studied. The amount adsorbed and the adsorption kinetics were measured using in situ ellipsometry. A substantial difference was seen between the two proteins. The adsorbed amount of the truncated version (2.53 mg/m2) indicates an end-on orientation, while the HCAIIpwt seems to adsorb side-on (1.84 mg/m2). It is suggested that the orientation effects arise from the truncation. The truncation is known to unfold the two most N-terminal helical segments, which could inhibit adsorption with the N-terminal region facing the surface, due to steric repulsion.
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| 4. |
- Billsten, Peter, et al.
(författare)
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Structural Changes of T4 Lysozyme upon Adsorption to Silica Nanoparticles Measured by Circular Dichroism
- 1995
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 175:1, s. 77-82
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Tidskriftsartikel (refereegranskat)abstract
- The change in the secondary structure of T4 lysozyme upon adsorption to silica particles was studied with circular dichroism. Two different mutants of the protein along with the wild type were investigated. The mutants differ from wild type by substitution of isoleucine for cysteine or tryptophan at position 3 and were chosen to represent a range of stability as quantified by their energies of thermal unfolding. The mutants differ in ΔG, at 65°C and pH 6.5, compared to the wild-type enzyme with -2.8 and 1.2 kcal/mol for the tryptophan and cysteine mutants, respectively. After adsorption to 9-nm silica nanoparticles for 90 min, a large change in the spectrum was observed for the less stable tryptophan mutant, while the changes were smaller for the wild type and the cysteine mutant. The spectral changes before and after adsorption corresponded to a calculated loss of α-helix of 12% for the wild type, 9% for the cysteine mutant, and 29% for the tryptophan mutant. Structural changes during adsorption of the proteins were also followed kinetically at 222 nm. The rate of conformational change differed among the three proteins and was fastest for the tryptophan mutant. In the case of the tryptophan mutant the time required for half of the measured change to occur was approximately 5 min, while for the cysteine mutant and the wild-type T4 lysozyme more than 10 min was required.
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| 6. |
- Elwing, H, et al.
(författare)
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Protein and detergent interaction phenomena on solid surfaces with gradients in chemical composition
- 1990
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Ingår i: Advances in Colloid and Interface Science. - 0001-8686 .- 1873-3727. ; 32, s. 317-339
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Tidskriftsartikel (refereegranskat)abstract
- We have recently described a new method for analysis of protein interaction on solid surfaces. The basic idea of the method is to make a gradient of chemical groups on the surface and to quantify protein adsorption along the gradient with the use of optical methods such as fluorescence measurements or ellipsometry. We have used the technique for experiments on protein adsorption and exchange, and detergent interaction on wettability gradients made on, e.g., silicon oxide surfaces. Several new observations were made which can not be observed without the use of the gradient method. This contribution is a short review of these obtaineer results and related research problems.
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| 7. |
- Hedlund, Julia, 1975, et al.
(författare)
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Change of Colloidal and Surface Properties of Mytilus edulis Foot Protein 1 in the Presence of an Oxidation (NaIO4) or a Complex-Binding (Cu2+) Agent
- 2009
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 10:4, s. 845-849
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Tidskriftsartikel (refereegranskat)abstract
- Quartz crystal microbalance with dissipation monitoring (QCM-D) was used to study the viscoelastic properties of the blue mussel, Mytilus edulis, foot protein 1 (Mefp-1) adsorbed on modified hydrophobic gold surfaces. The change in viscoelasticity was studied after addition of Cu2+ and Mn2+, which theoretically could induce metal complex formation with 3,4-dihydroxyphenylalanine (DOPA) moieties. We also used NaIO4, a nonmetal oxidative agent known to induce di-DOPA formation. Reduction in viscoelasticity of adsorbed Mefp-1 followed the order of NaIO4 > Cu2+ > buffer control > Mn2+. We also studied the formation of molecular aggregates of Mefp-1 in solution with the use of dynamic light scattering (DLS). We found that addition of Cu2+, but not Mn2+, induced the formation of larger DLS-detectable aggregates. Minor aggregate formation was found with NaIO4. With the analytical resolution of small angle X-ray scattering (SAXS), we could detect differences in the molecular structure between NaIO4- and Cu2+-treated Mefp-1 aggregates. We concluded from this study that Cu2+ could participate in intermolecular cross-linking of the Mefp-1 molecule via metal complex formation. Metal incorporation in the protein most likely increases the abrasion resistance of the Mefp-1 layer. NaIO4, on the other hand, resulted in mainly intramolecular formation of di-DOPA, but failed to induce larger intermolecular aggregation phenomena. The described methodological combination of surface sensitive methods, like QCM-D, and bulk sensitive methods, like DLS and SAXS, generates high resolution results and is an attractive platform to investigate intra- and intermolecular aspects of assembly and cross-linking of the Mefp proteins.
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| 9. |
- Lundgren, A., et al.
(författare)
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Resonance-Mode Electrochemical Impedance Measurements of Silicon Dioxide Supported Lipid Bilayer Formation and Ion Channel Mediated Charge Transport
- 2011
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 83:20, s. 7800-7806
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Tidskriftsartikel (refereegranskat)abstract
- A single-chip electrochemical method based on impedance measurements in resonance mode has been employed to study lipid monolayer and bilayer formation on hydrophobic alkanethiolate and SiO(2) substrates, respectively. The processes were monitored by temporally resolving changes in interfacial capacitance and resistance, revealing information about the rate of formation, coverage, and defect density (quality) of the layers at saturation. The resonance-based impedance measurements were shown to reveal significant differences in the layer formation process of bilayers made from (i) positively charged lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine (POEPC), (ii) neutral lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) on SiO(2), and (iii) monolayers made from POEPC on hydrophobic alkanethiolate substrates. The observed responses were represented with an equivalent circuit, suggesting that the differences primarily originate from the presence of a conductive aqueous layer between the lipid bilayers and the SiO(2). In addition, by adding the ion channel gramicidin D to bilayers supported on SiO(2), channel-mediated charge transport could be measured with high sensitivity (resolution around 1 pA).
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| 10. |
- Nilsson Ekdahl, Kristina, et al.
(författare)
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Innate immunity activation on biomaterial surfaces: A mechanistic model and coping strategies
- 2011
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Ingår i: Advanced Drug Delivery Reviews. - : Elsevier BV. - 0169-409X .- 1872-8294. ; 63:12, s. 1042-1050
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Forskningsöversikt (refereegranskat)abstract
- When an artificial biomaterial (e.g., a stent or implantable pump) is exposed to blood, plasma proteins immediately adhere to the surface, creating a new interface between the biomaterial and the blood. The recognition proteins within the complement and contact activation/coagulation cascade systems of the blood will be bound to, or inserted into, this protein film and generate different mediators that will activate polymorphonuclear leukocytes and monocytes, as well as platelets. Under clinical conditions, the ultimate outcome of these processes may be thrombotic and inflammatory reactions, and consequently the composition and conformation of the proteins in the initial layer formed on the surface will to a large extent determine the outcome of a treatment involving the biomaterial, affecting both the functionality of the material and the patient's life quality. This review presents models of biomaterial-induced activation processes and describes various strategies to attenuate potential adverse reactions by conjugating bioactive molecules to surfaces or by introducing nanostructures.
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