| 1. |
- Collin, Mattias, et al.
(författare)
-
Effect of SpeB and EndoS from Streptococcus pyogenes on human immunoglobulins
- 2001
-
Ingår i: Infection and Immunity. - 1098-5522. ; 69:11, s. 7187-7189
-
Tidskriftsartikel (refereegranskat)abstract
- Streptococcus pyogenes secretes a specific immunoglobulin G (IgG)-protease, SpeB, as well as the IgG glycan-hydrolyzing enzyme EndoS. Here we show that SpeB also degrades IgA, IgM, IgD, and IgE. We also show that EndoS only hydrolyzes the glycan moiety on native but not denatured IgG. Thus, SpeB has a broad immunoglobulin-degrading activity, while EndoS is highly specific for IgG.
|
|
| 2. |
- Collin, Mattias, et al.
(författare)
-
EndoS, a novel secreted protein from Streptococcus pyogenes with endoglycosidase activity on human IgG
- 2001
-
Ingår i: EMBO Journal. - : Wiley. - 1460-2075. ; 20:12, s. 3046-3055
-
Tidskriftsartikel (refereegranskat)abstract
- Streptococcus pyogenes is an important human pathogen that selectively interacts with proteins involved in the humoral defense system, such as immunoglobulins and complement factors. In this report we show that S.pyogenes has the ability to hydrolyze the chitobiose core of the asparagine-linked glycan on immuno globulin G (IgG) when bacteria are grown in the presence of human plasma. This activity is associated with the secretion of a novel 108 kDa protein denoted EndoS. EndoS has endoglycosidase activity on purified soluble IgG as well as IgG bound to the bacterial surface. EndoS is required for the activity on IgG, as an isogenic EndoS mutant could not hydrolyze the glycan on IgG. In addition, we show that the secreted streptococcal cysteine proteinase SpeB cleaves IgG in the hinge region in a papain-like manner. This is the first example of an endoglycosidase produced by a bacterial pathogen that selectively hydrolyzes human IgG, and reveals a novel mechanism which may contribute to S.pyogenes pathogenesis.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Collin, Mattias, et al.
(författare)
-
Generation of a mature streptococcal cysteine proteinase is dependent on cell wall-anchored M1 protein
- 2000
-
Ingår i: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 36:6, s. 1306-1318
-
Tidskriftsartikel (refereegranskat)abstract
- In the present study, we have generated a mutant strain of Streptococcus pyogenes, MC25, which lacks M protein on its surface, and we demonstrate that this strain is unable to generate a mature 28 kDa cysteine proteinase. Furthermore, we show that S. pyogenes bacteria of M1 serotype are dependent on cell wall-anchored M protein to cleave the secreted zymogen into a mature cysteine proteinase. We also show that MC25 secretes a 40 kDa zymogen, having a conformation different from that secreted by wild-type bacteria. We provide data showing that the cleavage site is not blocked but, presumably, the active site is. This suggests that M protein, when anchored to the cell wall, is involved in the unfolding of the zymogen and generation of a mature cysteine proteinase that can be activated under reducing conditions. Our data add new aspects to the interaction between two important virulence factors of S. pyogenes, the streptococcal cysteine proteinase and M protein.
|
|
| 6. |
- Collin, Mattias, et al.
(författare)
-
Identification of conditionally expressed genes in Streptococcus pyogenes using RNA fingerprinting
- 2001
-
Ingår i: FEMS Microbiology Letters. - 1574-6968. ; 196:2, s. 123-127
-
Tidskriftsartikel (refereegranskat)abstract
- RNA fingerprinting using arbitrarily primed reverse transcription-polymerase chain reaction was employed on isolated RNA from Streptococcus pyogenes bacteria in order to identify genes that were regulated in response to environmental changes. When S. pyogenes was cultured under glucose-rich growth conditions a number of transcriptionally up-regulated products were identified, cloned and sequenced. Using the Streptococcal Genome Sequencing Project database and similarity searches against the GenBank database the corresponding genes encoding enzyme IIB and IIC component of a putative phosphotransferase system were identified. Thus, we show that RNA fingerprinting could be a useful tool to identify unknown genes in S. pyogenes that are expressed under certain environmental conditions.
|
|
| 7. |
- Emadi, Arezoo, 1977, et al.
(författare)
-
High power HBV multipliers for F- and G- band applications
- 2004
-
Ingår i: IRMMW 2004/THz 2004 / M. Thumm, W. Wiesbeck. - 0780384903 ; , s. 319-320
-
Konferensbidrag (refereegranskat)abstract
- Progress and realisation of applications in the 100-240 GHz region is inhibited by the lack of high-power sources. Therefore, in an effort to reach watts of output power, we have tailored devices, circuits, materials, and design and fabrication methods for improved thermal management and high overall conversion efficiencies.
|
|
| 8. |
- Ingvarson, Mattias, 1974, et al.
(författare)
-
Design, analysis and modelling of heterostructure barrier varactors for sub-millimetre wave frequency quintuplers
- 2003
-
Ingår i: GigaHertz 2003, Linköping Electronic Conference Proceedings. - 1650-3740.
-
Konferensbidrag (refereegranskat)abstract
- We report on the design, modelling and analysis of heterostructure barrier varactor (HBV) frequency quintuplers with output frequencies in the sub-millimetre wave region. The HBV is a symmetric varactor, thus only odd harmonics are generated and no DC bias is required. By incorporating several barriers in the device, the HBV is also capable of handling higher power levels than conventional varactors. This makes the HBV superior to the conventional Schottky varactor for high order frequency multiplier circuits. We present analytical models, which can be used to calculate parameters such as optimum doping concentration, layer structure, device area and series resistance for HBVs, as well as to predict the performance with respect to conversion efficiencies and output power levels. These parameters are then further optimised by harmonic balance simulations in commercial microwave EDA tools, for which we have developed accurate device models. We investigate the influence of embedding impedance levels for optimum conversion efficiency by means of analytical expressions and harmonic balance simulations. Theoretical calculations predict a maximum diode conversion efficiency to 500 GHz for a planar, six-barrier InGaAs HBV of more than 30 %.
|
|
| 9. |
- Ingvarson, Mattias, 1974, et al.
(författare)
-
Design and analysis of 500 GHz heterostructure barrier varactor quintuplers
- 2003
-
Ingår i: Proceedings of the 14th International Symposium on Space Terahertz Technology.
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the design and analysis of heterostructure barrier varactor (HBV) frequency quintuplers with an output frequency of 500 GHz. The HBV is a symmetric varactor, thus only odd harmonics are generated and no DC bias is required. By incorporating several barriers in the device, the HBV is also capable of handling higher power levels than conventional varactors. This makes the HBV superior to the traditional Schottky varactor for high order frequency multiplier circuits. We present analytical, temperature dependent models, which can be used to calculate parameters such as optimum doping concentration, layer structure, device area and series resistance for HBVs, as well as to predict the performance with respect to conversion efficiencies and output power levels. These parameters are then further optimised by harmonic balance simulations in commercial microwave EDA tools, for which we have developed accurate device models. We investigate the influence of embedding impedance levels for optimum conversion efficiency by means of analytical expressions and harmonic balance simulations. Theoretical calculations predict a maximum diode conversion efficiency for a planar, six-barrier InGaAs HBV of more than 30%, for an input power level of 19 dBm. A waveguide circuit realisation of a 500 GHz HBV quintupler is presented.
|
|
| 10. |
- Ingvarson, Mattias, 1974, et al.
(författare)
-
Heterostructure barrier Varactor Frequency Multipliers: Materials, Devices and Circuits
- 2001
-
Ingår i: GigaHertz 2001.
-
Konferensbidrag (refereegranskat)abstract
- The Heterostructure Barrier Varactor, HBV, diode is used in frequency multipliers at millimetre and sub millimetre wavelengths. Owing to its symmetrical properties only odd harmonics are generated, this greatly simplifies the design of frequency triplers and quintuplers. We report on new InP based material and device designs for planar, whisker contacted, and novel pillar structure HBVs. We present design methods with measured and simulated results. We also report on a new waveguide frequency tripler where HBV diodes are embedded in a microstrip environment together with the matching network for the fundamental and the third harmonic. Simulated results are presented for this new circuit topology, which is highly suitable for system integration
|
|
