| 1. |
- Frankel, R., et al.
(författare)
-
Autocatalytic amplification of Alzheimer-associated A beta 42 peptide aggregation in human cerebrospinal fluid
- 2019
-
Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 2
-
Tidskriftsartikel (refereegranskat)abstract
- Alzheimer's disease is linked to amyloid beta (A beta) peptide aggregation in the brain, and a detailed understanding of the molecular mechanism of A beta aggregation may lead to improved diagnostics and therapeutics. While previous studies have been performed in pure buffer, we approach the mechanism in vivo using cerebrospinal fluid (CSF). We investigated the aggregation mechanism of A beta 42 in human CSF through kinetic experiments at several A beta 42 monomer concentrations (0.8-10 mu M). The data were subjected to global kinetic analysis and found consistent with an aggregation mechanism involving secondary nucleation of monomers on the fibril surface. A mechanism only including primary nucleation was ruled out. We find that the aggregation process is composed of the same microscopic steps in CSF as in pure buffer, but the rate constant of secondary nucleation is decreased. Most importantly, the autocatalytic amplification of aggregate number through catalysis on the fibril surface is prevalent also in CSF.
|
|
| 2. |
- Berggård, T, et al.
(författare)
-
Alpha1-microglobulin chromophores are located to three lysine residues semiburied in the lipocalin pocket and associated with a novel lipophilic compound
- 1999
-
Ingår i: Protein Science. - : Wiley. - 0961-8368. ; 8:12, s. 20-2611
-
Tidskriftsartikel (refereegranskat)abstract
- Alpha1-microglobulin (alpha1m) is an electrophoretically heterogeneous plasma protein. It belongs to the lipocalin superfamily, a group of proteins with a three-dimensional (3D) structure that forms an internal hydrophobic ligand-binding pocket. Alpha1m carries a covalently linked unidentified chromophore that gives the protein a characteristic brown color and extremely heterogeneous optical properties. Twenty-one different colored tryptic peptides corresponding to residues 88-94, 118-121, and 122-134 of human alpha1m were purified. In these peptides, the side chains of Lys92, Lys118, and Lys130 carried size heterogeneous, covalently attached, unidentified chromophores with molecular masses between 122 and 282 atomic mass units (amu). In addition, a previously unknown uncolored lipophilic 282 amu compound was found strongly, but noncovalently associated with the colored peptides. Uncolored tryptic peptides containing the same Lys residues were also purified. These peptides did not carry any additional mass (i.e., chromophore) suggesting that only a fraction of the Lys92, Lys118, and Lys130 are modified. The results can explain the size, charge, and optical heterogeneity of alpha1m. A 3D model of alpha1m, based on the structure of rat epididymal retinoic acid-binding protein (ERABP), suggests that Lys92, Lys118, and Lys130 are semiburied near the entrance of the lipocalin pocket. This was supported by the fluorescence spectra of alpha1m under native and denatured conditions, which indicated that the chromophores are buried, or semiburied, in the interior of the protein. In human plasma, approximately 50% of alpha1m is complex bound to IgA. Only the free alpha1m carried colored groups, whereas alpha1m linked to IgA was uncolored.
|
|
| 3. |
- Bratt, T, et al.
(författare)
-
Processing and secretion of rat alpha 1-microglobulin-bikunin expressed in eukaryotic cell lines
- 1994
-
Ingår i: FEBS Letters. - : Wiley. - 0014-5793. ; 354:1, s. 57-61
-
Tidskriftsartikel (refereegranskat)abstract
- The precursor protein alpha 1-microglobulin-bikunin was cleaved to the same degree whether expressed in CHO cells or in mutated CHO cells, RPE.40 cells, suggested to lack a functional form of the intracellular protease furin. Thus, alpha 1-microglobulin-bikunin probably is not cleaved in vivo by furin. However, simultaneous overexpression of the precursor and furin in COS, CHO and RPE.40 cells increased the cleavage, suggesting that compartmentalisation and concentrations of protease and precursor are important for the cleavage, besides the in vitro specificity. Expression of alpha 1-microglobulin and bikunin alone gave different protein patterns of SDS-PAGE as compared to expression of the precursor and subsequent cleavage, suggesting that the precursor protein is important for the post-translational handling of alpha 1-microglobulin and bikunin.
|
|
| 4. |
- Mattsson, Karin, et al.
(författare)
-
Translocation of 40 nm diameter nanowires through the intestinal epithelium of Daphnia magna
- 2016
-
Ingår i: Nanotoxicology. - : Informa UK Limited. - 1743-5390 .- 1743-5404. ; 10:8, s. 1160-1167
-
Tidskriftsartikel (refereegranskat)abstract
- Nanowires (NWs) have unique electrical and optical properties of value for many applications including lighting, sensing, and energy harnessing. Consumer products containing NWs increase the risk of NWs being released in the environment, especially into aquatic ecosystems through sewage systems. Daphnia magna is a common, cosmopolitan freshwater organism sensitive to toxicity tests and represents a likely entry point for nanoparticles into food webs of aquatic ecosystems. Here we have evaluated the effect of NW diameter on the gut penetrance of NWs in Daphnia magna. The animals were exposed to NWs of two diameters (40 and 80 nm) and similar length (3.6 and 3.8 μm, respectively) suspended in water. In order to locate the NWs in Daphnia, the NWs were designed to comprise one inherently fluorescent segment of gallium indium phosphide (GaInP) flanked by a gallium phosphide (GaP) segment. Daphnia mortality was assessed directly after 24 h of exposure and 7 days after exposure. Translocation of NWs across the intestinal epithelium was investigated using confocal fluorescence microscopy directly after 24 h of exposure and was observed in 89% of Daphnia exposed to 40 nm NWs and in 11% of Daphnia exposed to 80 nm NWs. A high degree of fragmentation was observed for NWs of both diameters after ingestion by the Daphnia, although 40 nm NWs were fragmented to a greater extent, which could possibly facilitate translocation across the intestinal epithelium. Our results show that the feeding behavior of animals may enhance the ability of NWs to penetrate biological barriers and that penetrance is governed by the NW diameter.
|
|
| 5. |
|
|
| 6. |
- Cedervall, T, et al.
(författare)
-
Allosteric and temperature effects on the plasma protein binding by streptococcal M protein family members
- 1995
-
Ingår i: Scandinavian Journal of Immunology. - : Wiley. - 0300-9475 .- 1365-3083. ; 42:4, s. 41-433
-
Tidskriftsartikel (refereegranskat)abstract
- Most group A streptococcal strains bind immunoglobulins (Ig) and fibrinogen to their cell walls. It is shown in this paper that the Ig-binding of three different strains was much weaker at 37 degrees C than at room temperature (20 degrees C), whereas the fibrinogen binding was unaffected by temperature. The binding properties and molecular sizes of two purified group A streptococcal cell surface proteins from the M protein family were studied at various temperatures, M1 protein with affinity for IgG, fibrinogen and albumin, and protein Sir22 with affinity for IgA and IgG. Both proteins appeared as monomers which bound all their ligands, including fibrinogen, very weakly at 37 degrees C, and as strongly binding dimers at 10 and 20 degrees C. Furthermore, the results demonstrated that the plasma protein binding of the bacterial proteins was allosterically regulated, i.e. the binding of a ligand to one site modulated the binding of a ligand to a second site. For example, the binding of albumin or IgG to purified M1 protein at 10 and 20 degrees C strongly enhanced the binding of fibrinogen at 37 degrees C. This indicates that the high affinity dimer form of the bacterial proteins can be stabilized at 37 degrees C, a possible explanation for the strong fibrinogen binding of whole bacteria. Finally, the sizes and binding properties of three M1 protein fragments were studied and the results indicated that the centrally located C-repeats, which are conserved among the members of the M protein family, are important for the formation of the high-affinity dimers of the bacterial proteins.
|
|
| 7. |
- Cedervall, T, et al.
(författare)
-
Coiled-coil structure of group A streptococcal M proteins. Different temperature stability of class A and C proteins by hydrophobic-nonhydrophobic amino acid substitutions at heptad positions a and d
- 1997
-
Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 36:16, s. 4987-4994
-
Tidskriftsartikel (refereegranskat)abstract
- M proteins and M-like proteins, expressed on the surface of group A streptococci and binding to human plasma proteins, can be divided into two classes, A and C, depending on the structure of the central repeated regions. The class C proteins have been shown to be dimers with a coiled-coil structure. In this work, we have compared the structure and binding of a class A protein, Mrp4, and a class C protein, Arp4, expressed by the same bacterial strain. Circular dichroism spectra, gel filtration, and binding assays showed that both proteins had a coiled-coil dimer configuration and a high-affinity binding at 20 degrees C. However, striking differences were seen at 37 degrees C. The class A protein, Mrp4, was still a coiled-coil dimer with high affinity binding activity, whereas the class C protein, Arp4, had lost both the coiled-coil structure and binding activity. Raising the temperature even higher, Mrp4 retained the coiled-coil structure up to 70-90 degrees C. Furthermore, a recombinant protein, Mrp(C), in which the A-repeats of Mrp4 were replaced by the C-repeats of Arp4, lost its coiled-coil structure and fibrinogen-binding around 40-45 degrees C. These results suggest a high thermal stability of class A proteins and a low stability of class C proteins and that the structural basis for this can be found partly in the A- and C-repeats. Analysis of the amino acid sequences of the A- and C-repeats, revealed a large difference, 87% and 45%, respectively, in the content of hydrophobic amino acid residues in the positions regarded as important for the formation of the coiled-coil structure. In particular, several alanine residues in the A-repeats were replaced by serine residues in the C-repeats. Our results suggest that important structural and functional changes within the M protein family have evolved by specific hydrophobic-nonhydrophobic amino acid replacements.
|
|
| 8. |
- Cedervall, Tommy, et al.
(författare)
-
Workshop on Environmental Nanosafety: Biological Interactions of Plastic Nanoparticles
- 2019
-
Ingår i: Journal of Chemical Education. - : American Chemical Society (ACS). - 0021-9584 .- 1938-1328. ; 96:9, s. 1967-1970
-
Tidskriftsartikel (refereegranskat)abstract
- The one-hour workshop, containing both a demonstration and hands-on experiments on the topic of nanosafety, is based on current science on a topic of general interest. The workshop aims to provide a deeper knowledge and understanding of nanoparticles. The participants get an introduction to what nanoparticles are, why nanosized materials are interesting, how nanomaterials interact with biological molecules, and potential risks associated with nanoparticles. Furthermore, by participating in the workshop the audience gains insights into how research about nanoparticles is conducted. The participants carry out experiments to demonstrate that daily-used plastic products can be disintegrated into particles in the nanometer size range, which may have important implications for the environment.
|
|
| 9. |
- Ekvall, Mikael T., et al.
(författare)
-
Adsorption of bio-organic eco-corona molecules reduces the toxic response to metallic nanoparticles in Daphnia magna
- 2021
-
Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- As the use of engineered nanomaterials increases, so does the risk of them spreading to natural ecosystems. Hitherto, knowledge regarding the toxic properties of nanoparticles (NP's) and their potential interactions with natural bio-organic molecules adsorbed to them, and thereby forming surface coronas, is limited. However, we show here that the toxic effect of NPs of tungsten carbide cobalt (WC-Co) and cobalt (Co) on the crustacean Daphnia magna is postponed in the presence of natural biological degradation products (eco-corona biomolecules). For Daphnia exposed to WC-Co NPs the survival time increased with 20-25% and for Co NPs with 30-47% after mixing the particles with a solution of eco-corona biomolecules before exposure. This suggests that an eco-corona, composed of biomolecules always present in natural ecosystems, reduces the toxic potency of both studied NPs. Further, the eco-coronas did not affect the particle uptake, suggesting that the reduction in toxicity was related to the particle-organism interaction after eco-corona formation. In a broader context, this implies that although the increasing use and production of NPs may constitute a novel, global environmental threat, the acute toxicity and long-term effects of some NPs will, at least under certain conditions, be reduced as they enter natural ecosystems.
|
|
| 10. |
- Ekvall, Mikael T., et al.
(författare)
-
Environmental impact of nanoplastics from fragmentized consumer plastics : Final project report
- 2022
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Misplaced plastics is an ongoing environmental problem. The breakdown of plastics into smaller pieces, microplastics, likely cause additional environmental burdens as they affect animals and plants at the beginning of the food chain. This may be even more true for the smallest of microplastics: the nano plastics as they will behave differently in nature and interact in new ways with organisms and potentially be taken up by the organisms and affect internal organs. The small size of nano plastics and their chemical resemblance with the surrounding environment makes them difficult to find, isolate and study. Most of what is known about nano plastics behavior in nature and their effect on nature derives from studies using commercially available polystyrene nanoparticles. These are probably different in many ways, such as structure, surface chemistry, and size distribution, compared to nano plastics broken down in nature from plastic debris. Despite this, we have used polystyrene nanoparticles to study knowledge gaps. The toxicity to zooplankton Daphnia magna (D. magna) of small positively charged amine-modified polystyrene nanoparticles is not affected by protein-induced aggregation. All tested polystyrene nanoparticles were toxic to D. magna regardless of their toxicity in acute tests. Proteins bound to polystyrene nanoparticles after filtration by D. magna were different on acutely and non-acutely toxic particles which may imply different mechanisms behind the toxicity. In order to study the effect of nano plastics that resemble what can be expected in nature we have mechanically broken down 8 different plastics and rubbers from 14 different consumer products and isolated the nano plastics. Careful characterization shows that the nano plastics are irregular in shape, have a slightly negative surface charge, and often have a strongly oxidized surface compared to the starting material. The nano sized fractions are not toxic to D. magna in the used concentrations. In contrary, for at least two plastics High Density Polyethylene (HDPE) and Polylactic acid (PLA) thoracoplasties increase the lifetime of the D. magna probably because the nano plastics can be utilized by bacteria which in turn serve as additional food for the zooplankton. However, leached additives and/or smaller polymers from HDPE are toxic to D. magna. We have also seen that UV irradiation further degrade polystyrene nanoparticles. The bacterial growth and the UV breakdown may imply that the nano plastics breakdown faster than believed in nature and that they with time may disappear.
|
|
