| 1. |
- Allhorn, Maria, et al.
(författare)
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EndoS from Streptococcus pyogenes is hydrolyzed by the cysteine proteinase SpeB and requires glutamic acid 235 and tryptophans for IgG glycan-hydrolyzing activity
- 2008
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Ingår i: BMC Microbiology. - : Springer Science and Business Media LLC. - 1471-2180. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: BACKGROUND: The endoglycosidase EndoS and the cysteine proteinase SpeB from the human pathogen Streptococcus pyogenes are functionally related in that they both hydrolyze IgG leading to impairment of opsonizing antibodies and thus enhance bacterial survival in human blood. In this study, we further investigated the relationship between EndoS and SpeB by examining their in vitro temporal production and stability and activity of EndoS. Furthermore, theoretical structure modeling of EndoS combined with site-directed mutagenesis and chemical blocking of amino acids was used to identify amino acids required for the IgG glycan-hydrolyzing activity of EndoS. RESULTS: We could show that during growth in vitro S. pyogenes secretes the IgG glycan-hydrolyzing endoglycosidase EndoS prior to the cysteine proteinase SpeB. Upon maturation SpeB hydrolyzes EndoS that then loses its IgG glycan-hydrolyzing activity. Sequence analysis and structural homology modeling of EndoS provided a basis for further analysis of the prerequisites for IgG glycan-hydrolysis. Site-directed mutagenesis and chemical modification of amino acids revealed that glutamic acid 235 is an essential catalytic residue, and that tryptophan residues, but not the abundant lysine or the single cysteine residues, are important for EndoS activity. CONCLUSIONS: We present novel information about the amino acid requirements for IgG glycan-hydrolyzing activity of the immunomodulating enzyme EndoS. Furthermore, we show that the cysteine proteinase SpeB processes/degrades EndoS and thus emphasize the importance of the SpeB as a degrading/processing enzyme of proteins from the bacterium itself.
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| 2. |
- Bryllert, Tomas, et al.
(författare)
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11% efficiency 100 GHz InP-based heterostructure barrier varactor quintupler
- 2005
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 0013-5194 .- 1350-911X. ; 41:3, s. 131-132
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Tidskriftsartikel (refereegranskat)abstract
- A record conversion efficiency of 11.4% at 100 GHz using a heterostructure barrier varactor (HBV) quintupler is demonstrated. The quintupler is based on a microstrip circuit mounted in a full-height crossed-waveguide block. The nonlinear element consists of a planar HBV diode fabricated in InGaAs=InAlAs=AlAs epitaxial layers on an InP substrate.
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| 3. |
- Emadi, Arezoo, 1977, et al.
(författare)
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Design, Fabrication and characterisation of High Power HBV Diodes
- 2005
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Ingår i: 16th International Symposium on Space Terahertz Technology; Chalmers Conference Centre, May 2-4, 2005, Gothenburg, Sweden, (Eds. Jan Stake, Harald Merkel.). ; , s. Session: P05-04
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Konferensbidrag (refereegranskat)abstract
- We present design and analysis of material structures and device geometries for heterostructure barrier varactor diodes (HBVs) for high-power frequency multipliers. The methods aim at finding optimum epitaxial layer structures with respect to diode power handling capability and efficiency. A distributed device geometry for further increasing the output power levels whilst maintaining acceptable device temperatures is also presented. Finally, an electro-thermal HBV model with the ability of incorporating temperature-dependent device parameters is used to simulate the introduced devices, followed by a design example of a 3×4-barrier high-power HBV diode.
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| 4. |
- Ingvarson, Mattias, 1974, et al.
(författare)
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An electro-thermal HBV model
- 2005
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Ingår i: IMS 2005. ; , s. 1151-1153
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Konferensbidrag (refereegranskat)
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| 5. |
- Kutty Selva, Nandakumar, et al.
(författare)
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Endoglycosidase treatment abrogates IgG arthritogenicity: Importance of IgG glycosylation in arthritis.
- 2007
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Ingår i: European Journal of Immunology. - Weinheim : Wiley. - 1521-4141 .- 0014-2980. ; 37:10, s. 2973-2982
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Tidskriftsartikel (refereegranskat)abstract
- The glycosylation status of IgG has been implicated in the pathology of rheumatoid arthritis. Earlier, we reported the identification of a novel secreted endo-beta-N-acetylglucosaminidase (EndoS), secreted by Streptococcus pyogenes that specifically hydrolyzes the beta-1,4-di-N-acetylchitobiose core of the asparagine-linked glycan of human IgG. Here, we analyzed the arthritogenicity of EndoS-treated collagen type II (CII) -specific mouse mAb in vivo. Endoglycosidase treatment of the antibodies inhibited the induction of arthritis in (BALB/c x B10.Q) F1 mice and induced a milder arthritis in B10.RIII mice as compared with the severe arthritis induced by non-treated antibodies. Furthermore, EndoS treatment did not affect the binding of IgG to CII and their ability to activate complement, but it resulted in reduced IgG binding to Fc gamma R and disturbed the formation of stable immune complexes. Hence, the asparagine-linked glycan on IgG plays a crucial role in the development of arthritis.
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| 6. |
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| 7. |
- Olsen, Arne, 1974, et al.
(författare)
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Compact frequency sources using high-order multipliers
- 2009
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Ingår i: 5th ESA Workshop on Millimetre Wave Technology and Applications. ; , s. 189-193
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Konferensbidrag (refereegranskat)abstract
- High-order multipliers are a suitable method for making compact frequency sources for high frequencies (> 100 GHz). A fixed frequency phased-locked source, where a fundamental source is multiplied up using among an in-house varactor diode multiplier, has a low phase noise and will be described in this article. These multipliers are based on the Heterostructure Barrier Varactor (HBV) diode, and can either triple or quintuple the frequency. Fixed frequencies from 90 to 220 GHz can be produced by using a combination of only one diode multiplier and a common source unit. A design rule for next generation of multipliers, where the power handling is emphasised, is also included. These multipliers will take the signal source up to a frequency of 500 GHz.
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| 8. |
- Olsen, Arne, 1974, et al.
(författare)
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HBV Frequency Quintuplers
- 2005
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Ingår i: 16th International Symposium on Space Terahertz Technology.
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Konferensbidrag (refereegranskat)abstract
- A 500 GHz heterostructure-barrier-varactor quintupler has been designed and fabricated. The design consists of a mixture of waveguide and microstrip components for impedance matching. A InP based HBV diode is flip-chip mounted onto the quartz circuit, where beam-leads are used for ground connections to the waveguide block. Extensive back-side processing has been carried out in order to create these beam-leads. The multiplier is a frequency scaled version of a successful 100 GHz quintupler with a conversion efficiency of 11.4%.
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| 9. |
- Sobis, Peter, 1978, et al.
(författare)
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Compact 340 GHz Receiver Front-Ends
- 2009
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Ingår i: 20th International Symposium on Space Terahertz Technology. ; , s. 183-189
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Konferensbidrag (refereegranskat)abstract
- A compact 340 GHz room temperature receiver front-end has been developed consisting of a subharmonic Schottky diode mixer module with an integrated LNA. A novel sideband separation topology has been evaluated by using a pair of the developed mixers interconnected by external waveguide branch guide coupler hybrids for the LO and RF feedings and coaxial IF hybrids, measuring sideband suppression levels of 5 dB to 15 dB over the 315-365 GHz band.For efficient LO pumping of the sideband separating mixer, a novel high power LO chain based on a 5 x 34 GHz HBV quintupler (170 GHz LO source) has been developed with an ultra compact mechanical block housing, not much larger then a waveguide flange. We have also looked into a broadband medium LO power source consisting of a W-band active multiplier module, based on commercial MMIC chips from Hittite, followed by a medium power Schottky doubler from VDI.The demonstrated compact receiver front end has a considerably reduced size and weight owing to the high multiplication factor of the compact LO chain and mixer with integrated LNA. The novel sideband separating topology that uses 90 degree hybrids for both LO and RF resolves the standing wave issue of a previously proposed topology, in which a matched Y-junction was used as an RF hybrid and a branch guide coupler with a 45 degree differential line phase shifter at the output, was used for the LO feeding. The proposed topology improves both the sideband suppression and reduces the standing waves at the LO and RF ports.
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| 10. |
- Stake, Jan, 1971, et al.
(författare)
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Development of high power HBV multipliers for millimeter wave applications
- 2007
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819468970 ; 6739, s. 67390U-
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Konferensbidrag (refereegranskat)abstract
- We present a high-power frequency tripler for 110 GHz and a quintupler for 200-210 GHz. The tripler (×3), that is based on a single HBV diode, produces 240 mW of output power with a 3-dB bandwidth of 6%. This is the highest output power ever recorded for an HBV based multiplier irrespective of output frequency. The module features an ultra-compact waveguide block design, and a microstrip matching circuit on high-thermal-conductivity AlN to improve the power handling capability. Furthermore, we present an HBV quintupler (×5) that delivers more than 20 mW at 202 GHz.
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