| 741. |
- Nadeem, Aftab, et al.
(författare)
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Protein-lipid interaction at low pH induces oligomerization of the MakA cytotoxin from Vibrio cholerae
- 2022
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Ingår i: eLIFE. - : eLife Sciences Publications, Ltd. - 2050-084X. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- The α-pore-forming toxins (α-PFTs) from pathogenic bacteria damage host cell membranes by pore formation. We demonstrate a remarkable, hitherto unknown mechanism by an α-PFT protein from Vibrio cholerae. As part of the MakA/B/E tripartite toxin, MakA is involved in membrane pore formation similar to other α-PFTs. In contrast, MakA in isolation induces tube-like structures in acidic endosomal compartments of epithelial cells in vitro. The present study unravels the dynamics of tubular growth, which occurs in a pH-, lipid-, and concentration-dependent manner. Within acidified organelle lumens or when incubated with cells in acidic media, MakA forms oligomers and remodels membranes into high-curvature tubes leading to loss of membrane integrity. A 3.7 Å cryo-electron microscopy structure of MakA filaments reveals a unique protein-lipid superstructure. MakA forms a pinecone-like spiral with a central cavity and a thin annular lipid bilayer embedded between the MakA transmembrane helices in its active α-PFT conformation. Our study provides insights into a novel tubulation mechanism of an α-PFT protein and a new mode of action by a secreted bacterial toxin.
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| 742. |
- Napoleone, Antonino, et al.
(författare)
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Fed-batch production assessment of a tetravalent bispecific antibody : A case study on piggyBac stably transfected HEK293 cells
- 2021
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Ingår i: New Biotechnology. - : Elsevier BV. - 1871-6784 .- 1876-4347. ; 65, s. 9-19
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Tidskriftsartikel (refereegranskat)abstract
- The transition from preclinical biological drug development into clinical trials requires an efficient upscaling process. In this context, bispecific antibody drugs are particularly challenging due to their propensity to form aggregates and generally produce low titers. Here, the upscaling process for a tetravalent bispecific antibody expressed by a piggyBac transposon-mediated stable HEK293 cell pool has been evaluated. The project was performed as a case study at Testa Center, a non-GMP facility for scale-up testing of biologics in Sweden, and encompassed media adaptation strategies, fed-batch optimization and a novel antibody purification technology. The cell pool was adapted to different culture media for evaluation in terms of cell viability and titers compared to its original Expi293 Expression Medium. These parameters were assessed in both sequential stepwise adaption and direct media exchanges. By this, a more affordable medium was identified that did not require stepwise adaptation and with similar titers and viability as in the Expi293 Expression Medium. Fed-batch optimizations resulted in culture densities reaching up to 20 x 106 viable cells/mL with over 90 % viability 12 days postinoculum, and antibody titers three times higher than corresponding batch cultures. By implementing a novel high-speed protein A fiber technology (Fibro PrismA) with a capture residence time of only 7.5 s, 8 L of supernatant could be purified in 4.5 h without compromising the purity, structural integrity and function of the bispecific antibody. Results from this study related to medium adaptation and design of fed-batch protocols will be highly beneficial during the forthcoming scale-up of this therapeutic antibody.
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| 743. |
- Naylor, Andrew Stuart, 1977, et al.
(författare)
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Extended voluntary running inhibits exercise-induced adult hippocampal progenitor proliferation in the spontaneously hypertensive rat.
- 2005
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 93:5, s. 2406-14
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Tidskriftsartikel (refereegranskat)abstract
- Previous work has shown that voluntary running increases cell proliferation and neurogenesis in the dentate gyrus of the adult hippocampus. Here we report that long-term running for 24 days results in a down-regulation of hippocampal progenitor proliferation to one-half the level of nonrunning controls compared with a fivefold increase in progenitor proliferation seen after 9 days of voluntary running (short-term running). The negative effects seen on proliferation after 24 days of running were prevented by restricting daily running distances (by 30-50%) during 24 days. Long-term running for 24 days increases the response of the hypothalamic-pituitary-adrenal axis, with an increase in adrenal gland weight and increased plasma corticosterone levels, as well as decreased thymus weight, indicating a stress response as a possible mediator of decreased progenitor proliferation. Furthermore, the negative effects seen on the observed stress response after 24 days of running were prevented by restricting daily running distance. Short-term running did not alter these stress parameters compared with nonrunning controls. However, it increased phosphorylated cyclic AMP response element binding protein (pCREB) in the dentate gyrus, an increase that was not seen in nonrunning controls or after 24 days of running. Taken together, these data suggest that voluntary running does not always enhance proliferation and that the decrease in progenitor proliferation seen in long-term running is possibly mediated by mechanisms involving a stress response in the animal. However, a moderate level of long-term running was able to prevent the negative stress-related changes seen in unrestricted long-term running.
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| 744. |
- Neely, D., et al.
(författare)
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Enhanced proton beams from ultrathin targets driven by high contrast laser pulses
- 2006
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89:2
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Tidskriftsartikel (refereegranskat)abstract
- The generation of proton beams from ultrathin targets, down to 20 nm in thickness, driven with ultrahigh contrast laser pulses is explored. the conversion efficiency from laser energy into protons increases as the foil thickness is decreased, with good beam quality and high efficiencies of 1% being achieved, for protons with kinetic energy exceeding 0.9 MeV, for 100 nm thick aluminum foils at intensities of 10(19) W/cm(2) with 33 fs, 0.3 J pulses. To minimize amplified spontaneous emission (ASE) induced effects disrupting the acceleration mechanism, exceptional laser to ASE intensity contrasts of up to 1010 are achieved by introducing a plasma mirror to the high contrast 10 Hz multiterawatt laser at the Lund Laser Centre. It is shown that for a given laser energy on target, regimes of higher laser-to-proton energy conversion efficiency. can be accessed with increasing contrast. The increasing efficiency as the target thickness decreases is closely correlated to an increasing proton temperature. (c) 2006 American Institute of Physics.
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| 745. |
- Neumüller, Magnus, et al.
(författare)
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HIV reverse transcriptase inhibiting antibodies detected by a new technique : relation to p24 and gp41 antibodies, HIV antigenemia and clinical variables.
- 1991
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Ingår i: Journal of Medical Virology. - : Wiley. - 0146-6615 .- 1096-9071. ; 34:1, s. 55-63
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Tidskriftsartikel (refereegranskat)abstract
- A new assay for HIV reverse transcriptase activity inhibiting antibodies (RTI-ab) was used for the analysis of a large collection of sera sampled before and after confirmation of HIV infection. In this assay HIV-RT was preincubated with diluted serum, after which residual RT activity was determined by a technique using a template coupled to macrobeads and 125I-lodo-deoxyuridine-triphosphate as the tracer-substrate. Of the 936 sera analysed, 818 were found positive for RTI-ab, and 824 were positive in Western blot (Wb). The prevalence of RTI-ab compared to Wb was therefore 99.3%. The corresponding figure for 930 sera analysed for envelope-ab, i.e., gp41-ab, was 823 positive, and of these 930 sera 815 were Wb positive, giving a comparative prevalence of 101%. In contrast, only 678 samples of 993 analyzed for core ab, i.e., p24, were positive, giving a prevalence of 77.0% as 880 of these samples were Wb positive. Thus, RTI-ab was as prevalent as gp41-ab, and although the analyses of RTI-ab amounts in different stages showed decreasing levels in stage IV compared to stages II or III, all of the sera except 1 were found positive in stages III and IV. Further, it was found that both the few RTI-ab negative samples in stage II and the few RTI-ab positive samples among Wb negative sera were sampled in connection with seroconversion. The specificity of the RTI-ab assay was 100% in a test of 200 serum samples from HIV negative blood donors. It was concluded that RTI-ab analyses can be made highly sensitive and specific and useful for studies of HIV infection.
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| 746. |
- Newie, Inga, et al.
(författare)
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The HER2-Encoded miR-4728-3p Regulates ESR1 through a Non-Canonical Internal Seed Interaction.
- 2014
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:5
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Tidskriftsartikel (refereegranskat)abstract
- Since the early 1980s remarkable progress has been made in understanding the role of the HER2 locus in carcinogenesis, but many details of its regulatory network are still elusive. We recently reported the finding of 367 new human microRNA (miRNA) genes of which one, mir-4728, is encoded in an intron of the HER2 gene. Here, we confirm that the HER2 oncogene is a bi-functional locus encoding the membrane receptor and a functional miRNA gene. We further show that miR-4728-3p has alternative functionalities depending on the region used for interaction with its target; the canonical seed between nucleotides 2-8 or a novel, more internal seed shifted to nucleotides 6-12. Analysis of public data shows that this internal seed region, although rare compared to the far more abundant canonical 2-8 seed interaction, can also direct targeted down-regulation by other miRNAs. Through the internal seed, miR-4728-3p regulates expression of estrogen receptor alpha, an interaction that would have remained undetected if classic rules for miRNA-target interaction had been applied. In summary, we present here an alternative mode of miRNA regulation and demonstrate this dual function of the HER2 locus, linking the two major biomarkers in breast cancer.
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| 747. |
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| 748. |
- Nguyen, Hugo, 1955-, et al.
(författare)
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Material- and fabrication-governed performance of a tunnelling magnetometer
- 2010
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Ingår i: Advances in Natural Sciences. - : Institute of Physics (IOP). - 2043-6254 .- 2043-6262. ; 1:4, s. 045006-
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Tidskriftsartikel (refereegranskat)abstract
- Miniaturization of sensitive magnetic sensors for nano- and picosatellites has come to the point where the traditional sensors with magnetic coils soon can be replaced. Thin film technology offers the possibility of making extremely small magnetic field sensors that employ the effect of anisotropic, giant and tunneling magnetoresistance (AMR, GMR and TMR). In this paper, the development status of sensors based on microelectromechanical systems technology (MEMS), starting from a TMR layer structure is presented. The sensors have been successfully fabricated and integrated onto an electronic circuit designed for space application. The system as a whole, and the sensors in particular, have not only been characterized with respect to sensitivity, resolution, and noise level, but also to launch vibration and space radiation. The sensor performance and limitations are strongly dependent on the deposited materials, sensor design, and fabrication process. Since the sensor elements are small and sensitive (with lateral dimensions of some tens of micrometres, and resolution of 100 pT at frequencies of MHz), they are also promising for other MEMS applications.
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| 749. |
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| 750. |
- Nguyen, Hugo, 1955-, et al.
(författare)
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Tailoring the properties of a magnetic tunnel junction to be used as a magnetic field sensor
- 2011
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Ingår i: Conf. on solid state physics and materials VII (SPMS 2011), Ho Chi Minh, 7-9 November 2011.
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Konferensbidrag (refereegranskat)abstract
- A magnetic tunnel junction (MTJ) can be used as an effective magnetic field sensor thank to its high magnetoresistance ratio. To be used as a magnetic field sensor in different applications, the possibility of tuning the performance of the MTJ is important. Different means of tuning, such as voltage and magnetic field biasing, can be used. In this work, an external magnetic field from a permanent magnet was used to bias the sensing layer of a MTJ along its hard axis, and the effect of the biasing on the sensitivity, detection limit, and hysteresis of the MTJ was investigated. The experiments showed that the hysteresis of the MTJ languished away at a certain applied magnetic field. Moreover, the sensitivity and noise level decreased, whereas the detection limit increased with increasing bias field strength. The motivation of this experiment is not only to find a power- and cost-effective method of tuning the MTJ, but also to study what happens with the sensing layer, and with electron transport within the MTJ when an external magnetic field is applied.
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