| 1. |
- Loren, N., et al.
(författare)
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Fluorescence recovery after photobleaching in material and life sciences: putting theory into practice
- 2015
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Ingår i: Quarterly Reviews of Biophysics. - : Cambridge University Press (CUP). - 0033-5835 .- 1469-8994. ; 48:3, s. 323-387
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescence recovery after photobleaching (FRAP) is a versatile tool for determining diffusion and interaction/binding properties in biological and material sciences. An understanding of the mechanisms controlling the diffusion requires a deep understanding of structure-interaction-diffusion relationships. In cell biology, for instance, this applies to the movement of proteins and lipids in the plasma membrane, cytoplasm and nucleus. In industrial applications related to pharmaceutics, foods, textiles, hygiene products and cosmetics, the diffusion of solutes and solvent molecules contributes strongly to the properties and functionality of the final product. All these systems are heterogeneous, and accurate quantification of the mass transport processes at the local level is therefore essential to the understanding of the properties of soft (bio)materials. FRAP is a commonly used fluorescence microscopy-based technique to determine local molecular transport at the micrometer scale. A brief high-intensity laser pulse is locally applied to the sample, causing substantial photobleaching of the fluorescent molecules within the illuminated area. This causes a local concentration gradient of fluorescent molecules, leading to diffusional influx of intact fluorophores from the local surroundings into the bleached area. Quantitative information on the molecular transport can be extracted from the time evolution of the fluorescence recovery in the bleached area using a suitable model. A multitude of FRAP models has been developed over the years, each based on specific assumptions. This makes it challenging for the non-specialist to decide which model is best suited for a particular application. Furthermore, there are many subtleties in performing accurate FRAP experiments. For these reasons, this review aims to provide an extensive tutorial covering the essential theoretical and practical aspects so as to enable accurate quantitative FRAP experiments for molecular transport measurements in soft (bio)materials.
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| 2. |
- Nisslert, R., et al.
(författare)
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Identification of the three-dimensional gel microstructure from transmission electron micrographs
- 2007
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Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 225:1, s. 42298-
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Tidskriftsartikel (refereegranskat)abstract
- Mass transport in gels depends crucially on local properties of the gel network. We propose a method for identifying the three-dimensional (3D) gel microstructure from statistical information in transmission electron micrographs. The gel strand network is modelled as a random graph with nodes and edges (branches). The distribution of edge length, the number of edges at nodes and the angles between edges at a node are estimated from transmission electron micrographs by image analysis methods. The 3D network is simulated by Markov chain Monte Carlo, with a probability function based on the statistical information found from the micrographs. The micrographs are projections of stained gel strands in slices, and we derive a formula for estimating the thickness of the stained gel slice based on the total projected gel strand length and the number of times that gel strands enter or exit the slice. © 2007 The Authors.
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| 3. |
- Bernin, Diana, 1979, et al.
(författare)
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Microstructure of polymer hydrogels studied by pulsed field gradient NMR diffusion and TEM methods
- 2011
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 7:12, s. 5711-5716
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Tidskriftsartikel (refereegranskat)abstract
- The microstructure of various alginate gels have been studied by pulsed field gradient NMR (PFG NMR) and transmission electron microscopy (TEM). The reduced diffusivity of dendrimer diffusion within the gels has been obtained from PFG NMR diffusion experiments. The polymer strand radius, an important microstructural property, has been extracted from various diffusion models. The results agree well with the polymer strand radii obtained from image analysis of the corresponding TEM micrographs.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
- Bergstrand, A., et al.
(författare)
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Aggregation behavior and size of lipopolysaccharide from Escherichia coli O55:B5
- 2006
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Ingår i: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 53:1, s. 42261-
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic light scattering, steady-state fluorescence, NMR diffusometry and cryo-TEM have been used to gain more insight into the aggregation behaviour of LPS from Escherichia coli O55:B5. Knowledge of this behaviour of the amphiphilic LPS molecule is in many cases of importance for the design of experiments and interpretation of results when using LPS in solution. The aim of this work was to study the aggregation and determine the aggregate size of E. coli O55:B5. The mean hydrodynamic radius of the LPS aggregates was determined by NMR diffusometry and dynamic light scattering to 14 and 26 nm, respectively. The cryo-TEM technique revealed predominately spherical aggregates of 9-19 nm. We wish to report 10 ?g/ml as the aggregation start for LPS E. coli O55:B5 in PBS buffer, pH 7.2. We suggest that the aggregation is a continuous process that starts at 10 ?g/ml and proceeds up to 300 ?g/ml. © 2006.
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| 8. |
- Folmer, B. M., et al.
(författare)
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Structure and dynamics of micelles and cubic phase structures with ethoxylated phytosterol surfactant in water
- 2008
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 24:13, s. 6441-6446
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Tidskriftsartikel (refereegranskat)abstract
- The self-assembly of a sterol ethoxylate surfactant with 30 oxyethylene units in water was studied by 1 H NMR self-diffusion measurements in a wide concentration range in the micellar region (0-25 wt %). The data showed that the surfactant aggregates do not interact by hard sphere interactions but rather a strong concentration dependence of the diffusion coefficient was noted which was explained by polymer scaling theory. In the cubic phase (30-65 wt %), the self-diffusion data from water, from surfactant, and from free polyoxyethylene suggest spherical micelles, although water diffusion was much restricted due to binding to the surfactant headgroup. From X-ray measurements in the cubic phase, the unit cell size was calculated, and together with surfactant self-diffusion measurements the exchange dynamics between free and aggregated surfactant was obtained. © 2008 American Chemical Society.
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| 9. |
- Folmer, BM, et al.
(författare)
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Micellization and adsorption of a series of fatty amide ethoxylates
- 2001
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Ingår i: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 242, s. 404-410
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Tidskriftsartikel (refereegranskat)abstract
- An in-depth study of the adsorption and micellization behaviour of a series of fatty amide ethoxylates is presented. The effect of the amide bond is studied as well as variations in unsaturations in the hydrocarbon chain and in the length of the oxyethylene headgroup. Ellipsometry is used to determine adsorption on a hydrophobic silica plate while 1H-NMR self-diffusion is used to study micelle size and structure. The amide bond was found to increase the hydrophilicity of the surfactant leading to less favourable packing at the interface. The micelles formed by these surfactants were more compact, compared to alcohol ethoxylates with the same hydrophobe. Effects of unsaturations on the interfacial packing were not be observed. The micelle structure was somewhat affected by the unsaturations due to increased bulkiness of the surfactant hydrophobe.
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| 10. |
- Hagslätt, H, et al.
(författare)
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Predictions of pulsed field gradient NMR echo-decays for molecules diffusing in various restrictive geometries. Simulations of diffusion propagators based on a finite element method
- 2003
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Ingår i: Journal of Magnetic Resonance. - 1096-0856. ; 161:2, s. 138-147
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Tidskriftsartikel (refereegranskat)abstract
- Pulsed field gradient NMR diffusometry is a promising tool for investigating structures of porous material through determinations of dynamic displacements of molecules in porous systems. A problem with this approach is the lack of closed analytical expressions for echo-decays in anything but idealized pore geometries. We present here an approach based on calculating the appropriate diffusion propagator by means of finite element calculations. The suggested method is quite general, and can be applied to arbitrary porous systems. The protocol for the calculations is outlined and we show results from some different cases: diffusion in confined geometries and in systems that are spatially inhomogeneous with respect to concentration.
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