| 1. |
- Gustafsson, Hanna, 1982, et al.
(author)
-
Mesoporous Silica Nanoparticles with Controllable Morphology Prepared from Oil-in-Water Emulsions
- 2016
-
In: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 467, s. 253-260
-
Journal article (peer-reviewed)abstract
- Mesoporous silica nanoparticles are an important class of materials with a wide range of applications. This paper presents a simple protocol for synthesis of particles as small as 40 nm and with a pore size that can be as large as 9 nm. Reaction conditions including type of surfactant, type of catalyst and presence of organic polymer were investigated in order to optimize the synthesis. An important aim of the work was to understand the mechanism behind the formation of these unusual structures and an explanation based on silica condensation in the small aqueous microemulsion droplets that are present inside the drops of an oil-in-water emulsion is put forward.
|
|
| 2. |
- Isaksson, Simon, 1988
(author)
-
Housing Aquaporins in Nanostructured Glass
- 2019
-
Doctoral thesis (other academic/artistic)abstract
- Proteins are a group of biomolecules that perform versatile tasks, which in many cases are essential for life. The magnitude of their importance is perhaps expressed by the word protein itself, coined by the Swedish chemist Jöns Jacob Berzelius in the summer of 1838. It is derived from the Greek word πρωτείος which means ‘primary’ or ‘of the highest importance’. By adding a different ending, Berzelius shaped the word protein which means ‘the most important building block in a thin thread’. The proteins of importance to this PhD thesis are aquaporins, whose primary function in nature is to sustain the osmotic balance across the cell membrane by transporting water. This transportation is highly energy efficient and selective compared to artificial processes, which renders aquaporins interesting from a water purification point of view. Many proteins, including aquaporins, are however not stable in non-native environments, which often results in protein degradation or aggregation upon use in synthetic environments. This is particularly prominent for membrane proteins, which need to be housed in an amphiphilic environment to function properly. This thesis explores aquaporin stabilization through different kinds of interactions with glass. Human Aquaporin 4 was either intercalated with a mesoporous silica substrate or covered in a thin layer of silica. In both cases, aquaporins were stabilized by a lipid bilayer that mimics its native cell membrane surroundings. This thesis also includes work on the first structural and functional characterization of Climbing Perch Aquaporin 1 and a synthesis method for producing uniform silica nanoparticles with accessible mesopores. Detailed characterization provided valuable information on different kinds of aquaporin-silica interactions. Aquaporins were, for instance, shown to extend into a porous silica substrate underneath a supported lipid bilayer. Furthermore, aquaporin secondary structure was preserved when stabilized by a silica shell. The findings in this thesis show that silica may be used as a biocompatible stabilization option for aquaporins, potentially paving the way for better aquaporin utilization in applications such as water purification.
|
|
| 3. |
- Isaksson, Simon, 1988, et al.
(author)
-
Protein-Containing Lipid Bilayers Intercalated with Size-Matched Mesoporous Silica Thin Films
- 2017
-
In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 17:1, s. 476-485
-
Journal article (peer-reviewed)abstract
- Proteins are key components in a multitude of biological processes, of which the functions carried out by transmembrane (membrane-spanning) proteins are especially demanding for investigations. This is because this class of protein needs to be incorporated into a lipid bilayer representing its native environment, and in addition, many experimental conditions also require a solid support for stabilization and analytical purposes. The solid support substrate may, however, limit the protein functionality due to protein material interactions and a lack of physical space. We have in this work tailored the pore size and pore ordering of a mesoporous silica thin film to match the native cell-membrane arrangement of the transmembrane protein human aquaporin 4 (hAQP4). Using neutron reflectivity (NR), we provide evidence of how substrate pores host the bulky water-soluble domain of hAQP4, which is shown to extend 7.2 nm into the pores of the substrate. Complementary surface analytical tools, including quartz crystal microbalance with dissipation monitoring (QCM-D) and fluorescence microscopy, revealed successful protein-containing supported lipid bilayer (pSLB) formation on mesoporous silica substrates, whereas pSLB formation was hampered on nonporous silica. Additionally, electron microscopy (TEM and SEM), light scattering (DLS and stopped-flow), and small-angle X-ray scattering (SAXS) were employed to provide a comprehensive characterization of this novel hybrid organic-inorganic interface, the tailoring of which is likely to be generally applicable to improve the function and stability of a broad range of membrane proteins containing water-soluble domains.
|
|
| 4. |
- Isaksson, Simon, 1988
(author)
-
Towards Energy-Efficient Drinking Water Production using Biomimicry
- 2017
-
Licentiate thesis (other academic/artistic)abstract
- Water is a prerequisite for life and we therefore need pure drinking water to survive. Yet there are more than half a billion people that do not have access to pure drinking water. Water treatment can be performed in many different ways, one of the most commonly used being filtration. As the climate is getting warmer and sources of fresh water are being increasingly contaminated, attention is shifted to the sea in the search for drinking water. Sea water does, however, need to be desalinated before it is usable as drinking water.Desalination is commonly conducted using the process of reverse osmosis (RO), where water is forced to penetrate water-selective barriers in filters. The main issues with reverse osmosis are that the pressure needed to drive the process against the osmotic pressure build-up is significant and that the diffusivity of water through the selectively permeable layer is relatively slow. The energy input needed to run a reverse osmosis process using saline sea water is therefore substantial and the process is mainly performed in large-scale desalination plants. A more energy-efficient solution is needed in order to produce drinking water in a more sustainable manner as well as on a smaller scale.Nature purifies water in a variety of ways such as large-scale water passage through sand and small-scale purification conducted by mussels. The aim of this thesis was to design a water filter using inspiration from nature. The model system of choice was the water transport across the cell membrane, which is present in both animals and plants. This water transport is conducted by transmembrane proteins called aquaporins, and the aim of this thesis was to incorporate aquaporins in a design that could potentially be used for water filtration purposes.This thesis proposes a design where aquaporins are supported by mesoporous silica in order to improve robustness. A straightforward assembly process was developed and the resulting design was evaluated using a range of characterization techniques. The results showed that the mesoporous substrate greatly facilitated the spontaneous rupture and bilayer formation from proteoliposomes. Furthermore, neutron reflectivity data provided evidence of protein–silica intercalation where aquaporins made use of the aqueous pore environment to host their extracellular domains. This behavior is thought to improve the robustness of the system. The proposed water filter design put forward in this thesis will hopefully prove useful in the production of drinking water in the future.
|
|
| 5. |
- Joyce, Paul, 1989, et al.
(author)
-
TIRF Microscopy-Based Monitoring of Drug Permeation Across a Lipid Membrane Supported on Mesoporous Silica
- 2021
-
In: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 60:4, s. 2069-2073
-
Journal article (peer-reviewed)abstract
- There is an urgent demand for analytic approaches that enable precise and representative quantification of the transport of biologically active compounds across cellular membranes. In this study, we established a new means to monitor membrane permeation kinetics, using total internal reflection fluorescence microscopy confined to a ≈500 nm thick mesoporous silica substrate, positioned underneath a planar supported cell membrane mimic. This way, we demonstrate spatiotemporally resolved membrane permeation kinetics of a small-molecule model drug, felodipine, while simultaneously controlling the integrity of, and monitoring the drug binding to, the cell membrane mimic. By contrasting the permeation behaviour of pure felodipine with felodipine coupled to the permeability enhancer caprylate (C8), we provide evidence for C8-facilitated transport across lipid membranes, thus validating the potential for this approach to successfully quantify carrier system-induced changes to cellular membrane permeation.
|
|
| 6. |
- Zeng, Jiao, et al.
(author)
-
High-resolution structure of a fish aquaporin reveals a novel extracellular fold
- 2022
-
In: Life Science Alliance. - : Life Science Alliance, LLC. - 2575-1077. ; 5:12
-
Journal article (peer-reviewed)abstract
- Aquaporins are protein channels embedded in the lipid bilayer in cells from all organisms on earth that are crucial for water homeostasis. In fish, aquaporins are believed to be important for osmoregulation; however, the molecular mechanism behind this is poorly understood. Here, we present the first structural and functional characterization of a fish aquaporin; cpAQP1aa from the fresh water fish climbing perch (Anabas testudineus), a species that is of high osmoregulatory interest because of its ability to spend time in seawater and on land. These studies show that cpAQP1aa is a water-specific aquaporin with a unique fold on the extracellular side that results in a constriction region. Functional analysis combined with molecular dynamic simulations suggests that phosphorylation at two sites causes structural perturbations in this region that may have implications for channel gating from the extracellular side.
|
|
