| 1. |
- Hahn Berg, IC, et al.
(författare)
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Ellipsometry and TIRF studies of enzymatic degradation of interfacial proteinaceous layers
- 2001
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 17, s. 1641-1652
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Tidskriftsartikel (refereegranskat)abstract
- Ellipsometry and total internal reflectance fluorescence spectroscopy (TIRF) have been employed to investigate the layer structure of gelatin adsorbed from aqueous solutions onto silica/glass and methylated silica/glass, as well as the effects of addition of the proteolytic enzymes krillase and trypsin, in relation to temperature, enzyme concentration and enzymatic activity. The results for the hydrophilic substrates show that homogeneous and heterogeneous exchange occurs readily, as does autolysis of trypsin at the interface. At the hydrophobic substrates, the effect of exchange is limited and a residual gelatin fraction is present at the interface throughout. The interfacial behavior of gelatin above and below the helix formation temperature (Thelix) shows that more extended surface layers are formed at both substrates below Thelix . At the hydrophilic substrates, the higher adsorbed layer thickness below Thelix is mainly due to the adsorption of more gelatin than at the higher temperature, whereas, at the hydrophobic substrates, the increase in layer thickness below Thelix is due to a decrease in packing density. Enzyme addition to preadsorbed gelatin at methylated silica results in the transition to a thinner and denser layer, that contains both residual gelatin and proteolytic enzymes (i.e., krillase or trypsin). At hydrophobic surfaces, a faster and more extensive degradation of the gelatin layer is observed with increasing krillase concentration, the effect of which is similar above and below Thelix . The effect of trypsin addition to preadsorbed gelatin is enhanced at TThelix . Finally, the exposure of preadsorbed gelatin to inactivated krillase showed a nearly complete elimination in the effects observed upon addition of intact krillase. This indicated that the enzymatic activity of krillase in its native form plays a major role for the interaction between krillase and preadsorbed gelatin.
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| 2. |
- Hahn Berg, IC, et al.
(författare)
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Intraoral lubrication of PRP-1, statherin and mucin as studied by AFM
- 2004
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Ingår i: Biofouling (Print). - 0892-7014 .- 1029-2454. ; 20, s. 65-70
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper was to elucidate the mechanisms behind salivary lubrication with special emphasis on the lubricity of three pellicle key components (human acidic proline-rich protein 1 (PRP-1), human statherin and bovine submaxillary mucin (BSM)). The lubricating properties of the proteins have been assessed by means of colloidal probe atomic force microscopy, and are discussed in relation to their adsorption behavior. To various extent, the investigated proteins all showed a lubricating effect when adsorbed to silica surfaces. For comparable concentrations, PRP-1 was found to have a more pronounced lubricating effect than BSM, which in turn showed a higher lubricity than statherin. The relative lubricity is in accordance with previously reported relative adsorbed amounts of the three proteins, within the investigated concentration interval. We conclude that PRP-1 has the highest lubricating capacity as a pure fraction among the investigated preparations, and that the lubricating effect of PRP-1 as a pure fraction is notably large as compared to the lubricity of human whole saliva
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| 3. |
- Hahn Berg, IC, 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). - 0892-7014 .- 1029-2454. ; 19, 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 as well as potential artificial saliva formulations. Here we measure normal as well as lateral forces, acting between adsorbed salivary films, for the first time by means of colloidal probe atomic force microscopy. We find 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 well 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 atomic force microscopy, which offers a direct and quantitative measure of the lubrication on 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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| 4. |
- Hahn Berg, IC, et al.
(författare)
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Proteolytic degradation of oral biofilms in vitro and in vivo: potential of proteases originating from Euphausia superba for plaque control
- 2001
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Ingår i: European Journal of Oral Sciences. - 0909-8836 .- 1600-0722. ; 109, s. 316-324
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with enzymatic removal of dental plaque, in vitro as well as in vivo, using proteases from the Antarctic krill shrimp (Euphausia superba), referred to as Krillase®. Krillase exhibits both endo- and exopeptidase activity but has no microbicidal effect. In model systems with pure cultures of oral microorganisms, Krillase demonstrated inhibition of microbial adhesion to saliva-coated hydroxyapatite. Furthermore, a protocol for the growth of reproducible in vitro plaque films has been developed, and effects of Krillase on the plaque film were investigated by means of scanning electron microscopy (SEM). The results showed that Krillase efficiently released microorganisms from plaque in vitro, the effect being dependent on the enzymatic activity. The surface energy of the substratum had a minor influence on the formation and removal of plaque in vitro. Ellipsometric studies on the formation and enzymatic removal of a salivary pellicle indicated that the enzymatic effect on plaque may partly depend on degradation of the salivary pellicle. Krillase was also able to remove plaque accumulated on dentures in vivo. Our results demonstrate the potential of Krillase for plaque control, and that these enzymes are worthy of further investigations including clinical studies and work to find a suitable vehicle
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| 5. |
- Hahn Berg, IC, et al.
(författare)
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Salivary protein adsorption onto hydroxyapatite and SDS-mediated elution studied by in situ ellipsometry
- 2001
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Ingår i: Biofouling (Print). - 0892-7014 .- 1029-2454. ; 17, s. 173-187
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Tidskriftsartikel (refereegranskat)abstract
- Whole unstimulated saliva from two donors was investigated both with respect to adsorption characteristics and SDS-induced elutability. Salivary protein adsorption onto hydroxyapatite (HA) discs was studied by means of in situ ellipsometry in the concentration range 0.1-20% saliva. The adsorbed amounts on HA were found to be similar to those on silica, but the rates of adsorption were lower. Protein adsorption was virtually unaffected by the presence of Na+, whereas Ca2+ induced nucleation of calcium phosphate at the surface, the deposition rate being influenced by the pellicle age but not by the presence of saliva in bulk solution. The SDS elutability of adsorbed pellicles was determined on HA as well as on silica surfaces. Desorption from both surfaces was found to occur in the same SDS concentration range, although a residual layer was observed on HA. The slight net positive charge and lower charge density of HA as compared to the strongly negatively charged silica, may, at least partly, account for this observation by causing a reduction in the repulsive force between protein-surfactant complexes and the surface. Interindividual differences, observed in the adsorption as well as elution experiments, are thought to relate to the compositional differences observed by SDS-PAGE
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| 6. |
- Karlsson, O. E., et al.
(författare)
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Metagenomic detection methods in biopreparedness outbreak scenarios
- 2013
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Ingår i: Biosecurity and bioterrorism. - : Mary Ann Liebert Inc. - 1538-7135 .- 1557-850X. ; 11:SUPPL. 1, s. S146-S157
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Tidskriftsartikel (refereegranskat)abstract
- In the field of diagnostic microbiology, rapid molecular methods are critically important for detecting pathogens. With rapid and accurate detection, preventive measures can be put in place early, thereby preventing loss of life and further spread of a disease. From a preparedness perspective, early detection and response are important in order to minimize the consequences. During the past 2 decades, advances in next-generation sequencing (NGS) technology have changed the playing field of molecular methods. Today, it is within reach to completely sequence the total microbiological content of a clinical sample, creating a metagenome, in a single week of laboratory work. As new technologies emerge, their dissemination and capacity building must be facilitated, and criteria for use, as well as guidelines on how to report results, must be established. This article focuses on the use of metagenomics, from sample collection to data analysis and to some extent NGS, for the detection of pathogens, the integration of the technique in outbreak response systems, and the risk-based evaluation of sample processing in routine diagnostics labs. The article covers recent advances in the field, current debate, gaps in research, and future directions. Examples of metagenomic detection, as well as possible applications of the methods, are described in various biopreparedness outbreak scenarios. © 2013, Mary Ann Liebert, Inc.
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| 7. |
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| 8. |
- Mellin, Pelle, et al.
(författare)
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Moisture content analysis of metal powders, using oven desorption followed by Karl Fischer titration
- 2018
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Ingår i: Euro PM 2018 Congress and Exhibition. - : European Powder Metallurgy Association (EPMA). - 9781899072507
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Konferensbidrag (refereegranskat)abstract
- In this paper, we use Oven Desorption followed by Karl Fischer Titration (KF), to measure moisture content in a newly opened PBF-LB Hasteloy X powder (we found 28.8 ppm), an PBF-EB powder (13.7 ppm) and a HIP powder (6.7 ppm). This method heats a powder sample inside a hermetically closed vial, in an oven. At the same time an inert gas flow enters, flushes out the evaporated water and exits the vial, via a double hollow needle. The gas-water mixture that exits is directed to the Karl Fischer Titration, where the evaporated moisture is quantified. Included is also a comparison with thermogravimetric analysis (TGA) and a climate chamber moisturization experiment of a PBF-LB HX powder followed by KF analysis. After the moisturization and KF analysis, the same powder was characterized in terms of oxygen content.
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| 9. |
- Van Den Berg, F. D., et al.
(författare)
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Product uniformity control - A research collaboration of european steel industries to non-destructive evaluation of microstructure and mechanical properties
- 2018
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Ingår i: Stud. Appl. Electromagn. Mech.. - : IOS Press. - 9781614998358 ; 43, s. 120-129
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Konferensbidrag (refereegranskat)abstract
- In steel manufacturing, the conventional method to determine the mechanical properties and microstructure is by offline, destructive (lab-)characterisation of sample material that is typically taken from the head or the tail of the coil. Since coils can be up to 7 km long, the samples are not always representative for the main coil body. Also, the time delay (typically a few days) between the actual production and the availability of the characterisation results implies that these results cannot be exploited for real-time adaptation of the process settings. Information about the microstructure and material properties can also be obtained from electromagnetic (EM) and ultrasonic (US) parameters, which can be measured in real-time, non-destructively, and over the full length of the steel strip product. With the aim to improve the consistency in product quality by use of inline EM and US measurements, a European project called "Product Uniformity Control" (PUC) has been set up as a broad collaboration between 4 major European Steel Manufacturers and 10 Universities / Research institutes. Using both numerical simulations and experimental characterisations, we study the inline measured EM and US parameters in regard of the microstructural and mechanical properties. In this way, we aim to establish an improved understanding of their mutual relationships, and to apply this knowledge in existing and new nondestructive evaluation techniques. In this paper, the concerted approach of modelling and experimental validation will be addressed, and results of this work will be shown in combination with inline measured data.
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| 10. |
- Vernet, Nicolas, et al.
(författare)
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Experimental determination of the permeability of engineering textiles : Benchmark II
- 2014
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier Ltd. - 1359-835X .- 1878-5840. ; 61, s. 172-184
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Tidskriftsartikel (refereegranskat)abstract
- In this second international permeability benchmark, the in-plane permeability values of a carbon fabric were studied by twelve research groups worldwide. One participant also investigated the deformation of the tested carbon fabric. The aim of this work was to obtain comparable results in order to make a step toward standardization of permeability measurements. Unidirectional injections were thus conducted to determine the unsaturated in-plane permeability tensor of the fabric. Procedures used by participants were specified in the guidelines defined for this benchmark. Participants were asked to use the same values for parameters such as fiber volume fraction, injection pressure and fluid viscosity to minimize sources of scatter. The comparison of the results from each participant was encouraging. The scatter between data obtained while respecting the guidelines was below 25%. However, a higher dispersion was observed when some parameters differed from the recommendations of this exercise.
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