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| 2. |
- Claesson, PM, et al.
(författare)
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Protein interactions at solid surfaces
- 1995
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Ingår i: Advances in Colloid and Interface Science. - 0001-8686 .- 1873-3727. ; 57, s. 161-227
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Tidskriftsartikel (refereegranskat)abstract
- In this review article we discuss a large number of the studies of interactions between protein-coated surfaces that has been presented in the literature. We also demonstrate how to relate surface force data to results from other techniques in order to provide a more full picture of protein behaviour at interfaces. One aim of the article is to discuss the experimental procedure and the difficulties with surface force measurements in protein systems. It is particularly important to point out how the sensitivity of this technique differs from that of other techniques, e.g. in determining structural changes in adsorbed proteins and in detecting proteins adsorbed on top of an inner firmly bound layer. It is also important to realize which surface force data that cannot be easily compared with findings from other techniques (one example is the kinetics of adsorption and desorption). We have tried to group proteins into different classes depending on their size and structure, and to try to find results that are common within these classes. It was found that some observations for unordered proteins with amphiphilic character, and for the small compact proteins, appear consistently within the respective class. Hence, for these types of protein common features/principles of the interfacial behaviour are identified. The very large and flexible glycoproteins behave in a similar way to synthetic polymers, but we found it hard to draw any firm conclusions based on the surface force studies presented so far. Perhaps, the most complicated surface behaviour is observed for soft globular proteins that undergo large scale conformational changes upon adsorption and when the layers are held under a high compressive force.
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| 3. |
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| 4. |
- Rippner Blomqvist, B., et al.
(författare)
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Ellipsometric characterization of ethylene oxide-butylene oxide diblock copolymer adsorption at the air-water interface
- 2005
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 21, s. 5061-5068
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Tidskriftsartikel (refereegranskat)abstract
- Ellipsometry was used to determine the adsorbed layer thickness (d) and the surface excess (adsorbed amount, ¡) of a nonionic diblock copolymer, E106B16, of poly(ethylene oxide) (E) and poly(butylene oxide) (B) at the air-water interface. The results were obtained (i) by the conventional ellipsometric evaluation procedure using the change of both ellipsometric angles and ¢ and (ii) by using the change of ¢ only and assuming values of the layer thickness. It was demonstrated that the calculated surface excesses from the different methods were in close agreement, independent of the evaluation procedure, with a plateau adsorption of about 2.5 mg/m2 (400 Å2/molecule). Furthermore, the amount of E106B16 adsorbed at the air-water interface was found to be almost identical to that adsorbed from aqueous solution onto a hydrophobic solid surface. In addition, the possibility to use combined measurements with H2O or D2O as substrates to calculate values of d and ¡ was investigated and discussed. We also briefly discuss within which limits the Gibbs equation can be used to determine the surface excess of polydisperse block copolymers
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| 5. |
- Auer, F, et al.
(författare)
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Switchable assembly of stable, ordered molecular layers
- 1999
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Ingår i: Chemistry - A European Journal. - 0947-6539 .- 1521-3765. ; 5, s. 1150-1159
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Tidskriftsartikel (refereegranskat)abstract
- Bisamidines can be assembled on self-assembled monolayers of mercaptoalkanoic acids on gold to form stable and ordered but pH-switchable layers (see diagram). At basic pH the layers are stable and charge selective towards charged surfactants and plasma proteins. The system can potentially be used to reversibly introduce new surface properties for given applications that use one single substrate.
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| 6. |
- Berg, I. C. H., et al.
(författare)
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Lubricating properties of the initial salivary pellicle - an AFM Study
- 2003
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Ingår i: Biofouling (Print). - : Informa UK Limited. - 0892-7014 .- 1029-2454. ; 19:6, s. 365-369
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Tidskriftsartikel (refereegranskat)abstract
- The role of saliva in the oral cavity is manifold; an important function is to serve as lubricant between hard (enamel) and soft (mucosal) tissues. Intraoral lubrication is of crucial importance in order to maintain functions such as deglutition, mastication and the faculty of speech. A large number of people suffer from impaired salivary functions, displaying symptoms such as 'dry mouth'. This results in a need for methods to assess the lubricating properties of both native saliva and potential artificial saliva formulations. Here, normal as well as lateral forces, acting between adsorbed salivary films, have been measured for the first time by means of colloidal probe atomic force microscopy (AFM). It was found that the presence of salivary pellicles between hard surfaces reduces the friction coefficient by a factor of 20. This reduction of friction is consistent with the long-range purely repulsive nature of the normal forces acting between the salivary films. The lubricating mechanism is presumably based on a full separation of the sliding surfaces by the salivary films. The friction between salivary films has been investigated at normal loads that cover the clinical jaw closing forces, and it can be concluded that the lubricating properties are maintained within this load interval. The present study indicates the usefulness of colloidal probe AFM, which offers a direct and quantitative measure of lubrication at a molecular level, in the study of biotribological phenomena. In particular, the results obtained here may have implications for the development of saliva substitutes.
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| 7. |
- 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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| 9. |
- Carlsson, F, et al.
(författare)
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Interactions between local anaesthetic agents and poly(N-isopropyl acrylamide) through phase behavior, surface tension, and adsorption measurements
- 2001
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 233, s. 320-328
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Tidskriftsartikel (refereegranskat)abstract
- he interaction between the local anaesthetic agents prilocaine and lidocaine, on one hand, and poly(N-isopropyl acrylamide) (pNIPAM), on the other, is investigated through studies of the polymer phase behavior and through surface tension and adsorption measurements. In particular, the cloud points (CP) for pNIPAM in the presence of lidocaine and prilocaine under different conditions were compared to the effects of electrolytes and alcohols. It was found that the electrolytes affect the CP of pNIPAM in a lyotropic manner, whereas alcohols depress the CP of pNIPAM in an alkyl chain length dependent way; i.e., the longer the chain, the larger the decrease in CP. Lidocaine and prilocaine affect the CP of pNIPAM in a pH-dependent manner. Below the p Ka of lidocaine and prilocaine, these cosolutes do not substantially affect the CP in the concentration range investigated, but rather behave analogous to simpler electrolytes. Above the p Ka, on the other hand, they strongly depress the CP already at low concentrations. In parallel, at low pH, the surface tension reduction due to lidocaine or prilocaine is marginal, whereas at high pH the surface tension is reduced considerably. Thus, the poor solubility of prilocaine and lidocaine at high pH causes these to become more surface active and simultaneously interact in a more pronounced way with pNIPAM. Furthermore, it was found from ellipsometry that an adsorbed pNIPAM layer contracts when lidocaine is added, presumably due to a lidocaine-pNIPAM interaction similar to that causing pNIPAM to phase separate. Analogous to this, it was demonstrated that an adsorbed pNIPAM layer shrinks and swells reversibly when the temperature is cycled above and beneath the CP.
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| 10. |
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