| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Henning-Knechtel, Anja, et al.
(författare)
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Designed Cell-Penetrating Peptide Inhibitors of Amyloid-beta Aggregation and Cytotoxicity
- 2020
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Ingår i: Cell Reports Physical Science. - : Elsevier BV. - 2666-3864. ; 1:2
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Tidskriftsartikel (refereegranskat)abstract
- Amyloid proteins and peptides are a major contributing factor to the development of various neurodegenerative disorders, including Alzheimer’s and prion diseases. Previously, a designed cell-penetrating peptide (CPP) comprising a hydrophobic signal sequence followed by a prion protein (PrP)-derived polycationic sequence (PrP23–28: KKRPKP) was shown to have potent anti-prion properties. Here, we extend this approach toward the amyloid-beta (Aβ) peptide amyloid formation, which is associated with Alzheimer’s disease. We characterized the interactions of the CPP with Aβ using complementary in vitro and in silico experiments. We report that the CPP stabilizes Aβ in a non-amyloid state and inhibits Aβ-induced neurotoxicity. Moreover, replacing PrP23–28 with a corresponding segment from Aβ results in a construct with similar CPP functionality and antagonism of Aβ aggregation and neurotoxicity. Our findings reveal a general underlying principle for inhibition of pathogenic protein aggregation that may facilitate the design of CPP-based therapeutics for amyloid diseases.
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| 3. |
- Kilk, Kalle, et al.
(författare)
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Cellular internalization of a cargo complex with a novel peptide derived from the third helix of the islet-1 homeodomain : Comparison with the penetratin peptide
- 2001
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Ingår i: Bioconjugate chemistry. - : American Chemical Society (ACS). - 1043-1802 .- 1520-4812. ; 12:6, s. 911-916
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Tidskriftsartikel (refereegranskat)abstract
- Cellular translocation into a human Bowes melanoma cell line was investigated and compared for penetratin and pIsl, two peptides that correspond to the third helices of the related homeodomains, from the Antennapedia transcription factor of Drosophila and the rat insulin-1 gene enhancer protein, respectively. Both biotinylated peptides internalized into the cells with similar efficacy, yielding an analogous intracellular distribution. When a large cargo protein, 63 kDa avidin, was coupled to either peptide, efficient cellular uptake for both the peptide−protein complexes was observed. The interactions between each peptide and SDS micelles were studied by fluorescence spectroscopy and acrylamide quenching of the intrinsic tryptophan (Trp) fluorescence. Both peptides interacted strongly and almost identically with the membrane mimicking environment. Compared to penetratin, the new transport peptide pIsl has only one Trp residue, which simplifies the interpretation of the fluorescence spectra and in addition has a native Cys residue, which may be used for alternative coupling reactions of cargoes of different character.
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| 4. |
- Król, Sylwia, et al.
(författare)
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The amyloid-inhibiting NCAM-PrP peptide targets Aβ peptide aggregation in membrane-mimetic environments
- 2021
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Ingår i: iScience. - : Elsevier BV. - 2589-0042. ; 24:8
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Tidskriftsartikel (refereegranskat)abstract
- Substantial research efforts have gone into elucidating the role of protein misfolding and self-assembly in the onset and progression of Alzheimer’s disease (AD). Aggregation of the Amyloid-β (Aβ) peptide into insoluble fibrils is closely associated with AD. Here, we use biophysical techniques to study a peptide-based approach to target Aβ amyloid aggregation. A peptide construct, NCAM-PrP, consists of a largely hydrophobic signal sequence linked to a positively charged hexapeptide. The NCAM-PrP peptide inhibits Aβ amyloid formation by forming aggregates which are unavailable for further amyloid aggregation. In a membrane-mimetic environment, Aβ and NCAM-PrP form specific heterooligomeric complexes, which are of lower aggregation states compared to Aβ homooligomers. The Aβ:NCAM-PrP interaction appears to take place on different aggregation states depending on the absence or presence of a membrane-mimicking environment. These insights can be useful for the development of potential future therapeutic strategies targeting Aβ at several aggregation states.
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| 5. |
- Lundberg, Pontus, et al.
(författare)
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Cell membrane translocation of the N-terminal (1-28) part of the prion protein
- 2002
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - 0006-291X .- 1090-2104. ; 299:1, s. 85-90
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Tidskriftsartikel (refereegranskat)abstract
- The N-terminal (1-28) part of the mouse prion protein (PrP) is a cell penetrating peptide, capable of transporting large hydrophilic cargoes through a cell membrane. Confocal fluorescence microscopy shows that it transports the protein avidin (67 kDa) into several cell lines. The (1-28) peptide has a strong tendency for aggregation and P-structure formation, particularly in interaction with negatively charged phospholipid membranes. The findings have implications for how prion proteins with uncleaved signal peptides in the N-termini may enter into cells, which is important for infection. The secondary structure conversion into beta-structure may be relevant as a seed for the conversion into the scrapie (PrPSc) form of the protein and its arnyloidic transformation.
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| 6. |
- Magzoub, Mazin, 1977-
(författare)
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Cell-penetrating peptides in model membrane systems : Interaction, structure induction and membrane effects
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Despite continuing advances in the development of macromolecules, including peptides, proteins, and oligonucleotides, for therapeutic purposes, the successful application of these hydrophilic molecules has so far been hampered by their inability to efficiently traverse the plasma membrane. The discovery of a class of peptides (cell-penetrating peptides, CPPs) with the ability to mediate the non-invasive and efficient import of a whole host of cargoes, both in vitro and in vivo, has provided a new means by which the problem associated with cellular delivery can be circumvented.A complete understanding of the translocation mechanism(s) of CPPs has so far proven elusive. Initial studies indicated an ATP-independent, non-endocytotic mechanism, dependent on direct peptide-membrane interactions, making it an enticing challenge from a biophysical point of view. To gain an insight into this mechanism, we identified three new CPP sequences, one corresponding to the third helix of the Islet-1 homeodomain, the other two corresponding to the unprocessed N-termini of the mouse and bovine PrPs, denoted mPrPp and bPrPp, respectively. We then investigated the membrane interactions of these peptides, comparing them to two well-characterized CPPs, the Antennapedia homeodomain-derived pAntp, and the chimeric transportan, in a variety of model membrane systems, using several spectroscopic techniques. Both pAntp and transportan were found to reside in the headgroup region of the bilayer, oriented along the surface (perpendicular to the bilayer normal). However, differences were observed between the peptides – with the homeodomain-derived peptides, pAntp and pIsl, on the one hand, and transportan and the prion-derived peptides on the other – in terms of their membrane interactions, in particular their membrane perturbation effects. These differences suggest that the peptides belong to two classes of CPPs that translocate through different mechanisms. This hypothesis was given further substance by the recent re-evaluation of the translocation mechanism, which led to the conclusion that many peptides, including pAntp, translocate by an energy-dependent, endocytotic mechanism. Interesting structural behaviour was observed for the homeodomain-derived CPPs, where they readily underwent an α → β structural conversion, depending on experimental conditions. High peptide concentration and/or high negative membrane surface charge was found to promote β-sheet structure. This structural conversion characteristic was shared by the prion-derived peptides, which along with their CPP property and their membrane perturbation effects, may have implications for the infectivity and toxicity associated with prion diseases.
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