| 1. |
- Soininen, Antti J., et al.
(författare)
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Dynamics of water confined in mesoporous magnesium carbonate
- 2016
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 145:23
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the dynamics of water confined in a porous magnesium carbonate material, Upsalite (R), using the high-resolution neutron backscattering spectrometer SPHERES. We found quasielastic scattering that does not flatten out up to 360 K, which means that the dynamics of water are much slower than in other matrix materials. Specifically, a single Lorentzian line could be fitted to the quasielastic part of the acquired spectra between 220 and 360 K. This, accompanied by an elastic line from dynamically frozen water present at all experimental temperatures, even above the melting point, signaled a significant amount of bound or slow water.
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| 2. |
- Hong, Liang, et al.
(författare)
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Structure and Dynamics of a Compact State of a Multidomain Protein, the Mercuric Ion Reductase
- 2014
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Ingår i: Biophysical Journal. - : Elsevier BV. - 1542-0086 .- 0006-3495. ; 107:2, s. 393-400
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Tidskriftsartikel (refereegranskat)abstract
- The functional efficacy of colocalized, linked protein domains is dependent on linker flexibility and system compaction. However, the detailed characterization of these properties in aqueous solution presents an enduring challenge. Here, we employ a novel, to our knowledge, combination of complementary techniques, including small-angle neutron scattering, neutron spin-echo spectroscopy, and all-atom molecular dynamics and coarse-grained simulation, to identify and characterize in detail the structure and dynamics of a compact form of mercuric ion reductase (MerA), an enzyme central to bacterial mercury resistance. MerA possesses metallochaperone-like N-terminal domains (NmerA) tethered to its catalytic core domain by linkers. The NmerA domains are found to interact principally through electrostatic interactions with the core, leashed by the linkers so as to subdiffuse on the surface over an area close to the core C-terminal Hg(II)-binding cysteines. How this compact, dynamical arrangement may facilitate delivery of Hg(II) from NmerA to the core domain is discussed.
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| 3. |
- Luchini, Alessandra, et al.
(författare)
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Neutron Reflectometry reveals the interaction between functionalized SPIONs and the surface of lipid bilayers
- 2017
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Ingår i: Colloids and Surfaces B. - : ELSEVIER SCIENCE BV. - 0927-7765 .- 1873-4367. ; 151, s. 76-87
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Tidskriftsartikel (refereegranskat)abstract
- The safe application of nanotechnology devices in biomedicine requires fundamental understanding on how they interact with and affect the different components of biological systems. In this respect, the cellular membrane, the cell envelope, certainly represents an important target or barrier for nanosystems. Here we report on the interaction between functionalized SuperParamagnetic Iron Oxide Nanoparticles (SPIONs), promising contrast agents for Magnetic Resonance Imaging (MRI), and lipid bilayers that mimic the plasma membrane. Neutron Reflectometry, supported by Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) experiments, was used to characterize this interaction by varying both SPION coating and lipid bilayer composition. In particular, the interaction of two different SPIONs, functionalized with a cationic surfactant and a zwitterionic phospholipid, and lipid bilayers, containing different amount of cholesterol, were compared. The obtained results were further validated by Dynamic Light Scattering (DLS) measurements and Cryogenic Transmission Electron Microscopy (Cryo-TEM) images. None of the investigated functionalized SPIONs were found to disrupt the lipid membrane. However, in all case we observed the attachment of the functionalized SPIONs onto the surface of the bilayers, which was affected by the bilayer rigidity, i.e. the cholesterol concentration.
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| 4. |
- Schmutzler, Tilo, et al.
(författare)
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The influence of n-hexanol on the morphology and composition of CTAB micelles
- 2018
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 543, s. 56-63
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the addition of n-hexanol as co-surfactant on the structure of cetyltrimethylammonium bromide (CTAB) micelles has been studied using small-angle X-ray and neutron scattering (SAXS, SANS). Contrast variation neutron scattering experiments were performed to determine the structure of both pure CTAB and n-hexanol modified CTAB micelles. The incorporation of n-hexanol leads to an elongation of the ellipsoidal CTAB micelles. The scattering length density of the micellar shell linearly depends on the degree of deuteration of the dispersion medium water and revealed the existence of substantial amounts of water in the micellar shell. The water content in the shell increased from 20 vol-% observed for pure CTAB micelles to 44 vol-% found for n-hexanol modified CTAB micelles. The amount of n-hexanol in the micellar shell was determined by varying the amount of fully deuterated and protonated n-hexanol. These experiments revealed a volume fraction of 26 vol-% of n-hexanol molecules in the micellar core which equals a molar fraction of 50 % n-hexanol within the CTAB micelles. The total composition of micellar core and shell was estimated. The packing density of headgroups, water molecules and bromide ions turned out to drastically increase in n-hexanol modified CTAB micelles. These findings contribute to a fundamental understanding of the stabilization mechanism of micelles by alcoholic co-surfactants and the resulting alteration of the morphology and interface composition. These results will facilitate the optimization of processes where CTAB and other comparable surfactants are used as phase transfer catalysts, structure directing agents or stabilizers in colloidal dispersions or emulsions.
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