1. |
- Hakansson, M C, et al.
(författare)
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The electronic structure of In- and As-terminated InAs(001) surfaces
- 1997
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 374:1-3, s. 73-79
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Tidskriftsartikel (refereegranskat)abstract
- The InAs(001) 2 x 4 and 4 x 2 surfaces have been investigated by angle-resolved photoemission. The X(3) and X(5) points were found to be located 6.0 and 2.7 eV below the valence band maximum, respectively, and the dispersion of bulk bands along the Gamma-X direction in the bulk Brillouin zone were well described by a theoretical calculation. From angle-resolved valence band spectra measured along the high symmetry directions [110] and [1(1) over bar0$], three surface induced stares were identified on both the InAs(001)4 x 2 and the InAs(001)2 x 4 surface. (C) 1997 Elsevier Science B.V.
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2. |
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3. |
- Andersson, C B M, et al.
(författare)
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Surface atomic structure of InAs((111)over-bar)2x2 and InSb((111)over-bar)2x2 studied by core level spectroscopy
- 1996
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 347:1-2, s. 199-206
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Tidskriftsartikel (refereegranskat)abstract
- Surface sensitive high resolution core level spectroscopy has been applied to the molecular beam epitaxy grown InAs((111) over bar)2 x 2 and InSb((111) over bar)2 x 2 surfaces. For both systems the In 4d core level consists of one dominating component while the Group V core levels are deconvoluted into four components. This analysis is consistent with a surface model where the topmost layer consists entirely of arsenic or antimony. In this model, Group V atoms form trimers bound to Group V atoms in the first double layer, leaving a single Group V rest atom per unit cell.
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4. |
- Olsson, L O, et al.
(författare)
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Charge accumulation at InAs surfaces
- 1996
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 76:19, s. 3626-3629
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Tidskriftsartikel (refereegranskat)abstract
- Angle-resolved photoelectron spectroscopy has been used to directly prove the existence of a charge accumulation layer at clean InAs surfaces. The formation of an accumulation layer is shown to be a common property of polar InAs surfaces, with the precise surface Fermi level position above the conduction band minimum determined by the surface geometry. The emission from states in the accumulation layer is studied with respect to its photon energy and angular dependence.
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5. |
- Olsson, L O, et al.
(författare)
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Core level and valence-band studies of the (111)2x2 surfaces of InSb and InAs
- 1996
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 53:8, s. 4734-4740
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Tidskriftsartikel (refereegranskat)abstract
- The valence and core electronic surface states on the (111)2X2 surfaces of InSb and InAs have been studied by angle-resolved photoelectron spectroscopy. Similarities in data show that the vacancy-buckling model, which is known to describe the InSb(111)2x2 surface, also applies to InAs(111)2X2. Three surface valence bands are identified and their dispersions are mapped along symmetry directions in the surface Brillouin zone. The In 4d core levels show one surface shifted component while no surface shifted components of the Sb 4d or As 3d core levels could be resolved.
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6. |
- Varekamp, P R, et al.
(författare)
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Angle-resolved photoemission spectroscopy of the 1x1 ordered overlayers on iodine-saturated GaAs(001) and InAs(001)
- 1996
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 352, s. 387-390
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Tidskriftsartikel (refereegranskat)abstract
- Angle-resolved valence band photoelectron spectra are collected from 1 X 1 ordered overlayers on I-2-saturated GaAs(001)-4 x 1, -c(2 X 8), and InAs(001)-c(8 x 2). A high-intensity dispersive surface state, located approximately 4.4 eV below the valence band maximum, is observed in each case. The state passes through an open lens in the projected bulk density of states and disperses symmetrically around the surface Brillouin zone edge. For all surfaces studied, the state is stronger when excited with the electric field polarized in the [110], as compared to the <(1)over bar 10>], azimuth. Since the state is independent of the termination of the initial surface, and since iodine bonds primarily to the outermost element, the state must result from delocalization of the electron states in the overlayer, and is not related to bonding with the substrate.
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7. |
- Adell, M, et al.
(författare)
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Photoemission studies of the annealing-induced modifications of Ga0.95Mn0.05As
- 2004
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 70:12: 125204
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Tidskriftsartikel (refereegranskat)abstract
- Using angle resolved photoemission we have investigated annealing-induced changes in Ga1-xMnxAs with x=0.05. We find that the position of the Fermi energy is a function of annealing time and temperature. It is also established that the Curie temperature is strongly correlated to the separation between the Fermi level and the valence band maximum. Valence band photoemission shows that the Mn3d spectrum is modified by the annealing treatments.
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8. |
- Adell, M., et al.
(författare)
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Photoemission study of the valence band offset between low temperature GaAs and (GaMn)As
- 2006
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89:17
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Tidskriftsartikel (refereegranskat)abstract
- Using synchrotron based photoelectron spectroscopy (GaMn) AsGaAs interfaces prepared in situ by low temperature molecular beam epitaxy have been studied. No band offset between the two systems is observed. The continuous transition is explained as an effect of dilution of the (GaMn)As by GaAs adlayers.
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9. |
- ANDERSSON, CBM, et al.
(författare)
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CORE-LEVEL PHOTOEMISSION FROM (III)-TYPE INAS SURFACES
- 1994
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 4:C9, s. 209-212
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Tidskriftsartikel (refereegranskat)abstract
- The InAs(111)2x2 and InAs(($$$) over bar 111)1x1 surfaces have been studied with high resolution core level spectroscopy. For the InAs(($$$) over bar 111)1x1 surface both the In 4d and the As 3d core levels display strong surface core level shifts, while for the InAs(111)2x2 surface only the In 4d level shows a detectable surface shift. The results indicate that the InAs(($$$) over bar 111)1x1 surface is relaxed, with atom layer displacement extending to subsurface layers. Unexpectedly, we find no surface shifted anion core level for the InAs(111)2x2 surface.
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10. |
- ANDERSSON, CBM, et al.
(författare)
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SPUTTERED AND ANNEALED INAS(111)OVER-BAR - AN UNRECONSTRUCTED SURFACE
- 1994
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 307, s. 885-889
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of the InAs(111BAR)1 X 1 surface has been investigated by angle resolved photoelectron spectroscopy along the symmetry lines GAMMAKBAR, GAMMAMBAR, and GAMMAMBAR of the surface Brillouin zone. The bulk valence band structure was calculated using a combination of the linear augmented plane-wave method and the relativistic augmented plane-wave method. We have projected the theoretical bulk band structure onto the surface Brillouin zone to separate surface states from surface resonances. Two surface related structures, S1 and S2, have been observed and their E(i)(k(parallel-to)) dispersions are established. Both S1 and S2 show the symmetry of the 1 X 1 surface Brillouin zone, which is consistent with the observed 1 X 1 LEED pattern. We identify S1 as the As-derived dangling bond state, and S2 is associated with the backbonds connecting the As atoms in the surface layer with the underlying In layer.
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11. |
- Asklund, H, et al.
(författare)
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Photoemission study of GaAs (100) grown at low temperature
- 2002
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 65:11
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Tidskriftsartikel (refereegranskat)abstract
- GaAs(100) layers grown by low-temperature (LT) molecular beam epitaxy were studied by means of valence-band and core-level photoelectron spectroscopy. Small differences were found between valence-band spectra from the LT layers and corresponding layers grown at high temperature. In the Ga 3d spectra a new component was found in the LT-GaAs. The relative intensity of this component was found to be practically constant with varying probing depth. It is proposed that this component represents sites coordinated to the five-atom As clusters formed at As-Ga antisites. This interpretation implies a higher density of antisite defects in the near-surface region than typically found in the bulk.
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12. |
- Chauhan, H. S., et al.
(författare)
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Direct- and inverse-photoemission investigations of the electronic structure of Cd(0001)
- 1993
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 48:7, s. 4729-4734
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Tidskriftsartikel (refereegranskat)abstract
- Photoemission and inverse angle-resolved photoemission spectra are presented for Cd(0001). The data are interpreted in terms of interband transitions, density-of-states effects, and excitations of surface states.
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13. |
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14. |
- Guziewicz, E., et al.
(författare)
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Mn on the surface of ZnO(0001) - a resonant photoemisson study
- 2005
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; T115, s. 541-544
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of Mn/ZnO system has been invesigated by synchrotron radiation photoemission. Manganese vacuum deposition was done at room temperature onto a ZnO(0001) single crystal for coverage Mn-Theta <= 4 ML. Photoemission spectra taken near the Mn3p-Mn3d absorption edge after each deposition step show resonant enhancement of Mn3d states within 10 eV of the Fermi edge. The experimentally deduced partial Mn3d density of states for Theta >= 1.2 ML shows at least three features: a major Mn3d structure at 3.8-4.5 eV below the Fermi edge, a valence structure at lower binding energy (1-3 eV) and a broad satelite in the 5.5-9 eV range. The branching ratio of satellite/main structure increases with depostion from 0.33 for 0.4 ML to 0.65 for 4 ML. After annealing up to 500 degrees C the satellite/main ratio decreases to 0.43 indicating a high degree of hybridization between the Mn3d states and valence band of ZnO. After annealing no manganese cap layer was found at the crystal surfaces as was confirmed by the lack of metallic Fermi edge in photoemission spectra and by scanning Auger spectroscopy experiment. The photoemission Mn3p core level spectra taken after annealing consist of two components separated by about 4 eV, which shows that at least two manganese states are observed in the Mn-ZnO interface region.
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15. |
- He, Z Q, et al.
(författare)
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As overlayer on GaAs(110) studied with photoemission
- 1995
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 52:23, s. 16602-16607
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Tidskriftsartikel (refereegranskat)abstract
- As-terminated GaAs(110) surfaces were prepared on ex situ cleaved substrates by molecular-beam epitaxy. The surface stoichiometry was controlled by postgrowth As deposition. Photoemission from a surface covered with a monolayer As was investigated in detail using synchrotron radiation. Two different surface components were found in core-level spectra, which are interpreted as due to adatoms bonding to the surface anions and cations. In the valence-band spectra several surface states were identified, in analogy with previous reports on the isoelectronic Sb/GaAs(110) system. The polarization dependence is not the same, however, which leads us to the conclusion that the adlayer bonding mechanisms are different in the two cases.
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16. |
- He, Z Q, et al.
(författare)
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Band structure evolution in InAs overlayers on GaAs(110)
- 1996
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 104, s. 608-614
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Tidskriftsartikel (refereegranskat)abstract
- An angle-resolved photoemission study of MBE grown InAs/GaAs(110) hetero-structures was carried out to investigate the establishment of valence bands as a function of overlayer thickness. The valence band spectra were found to change gradually up to thicknesses well above 10 nm. The data are interpreted in terms of excitations within the overlayer from a combination of substrate and overlayer initial states, the former tailing into the overlayer.
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17. |
- Ilver, D, et al.
(författare)
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Helicobacter pylori adhesin binding fucosylated histo-blood group antigens revealed by retagging
- 1998
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 279:5349, s. 373-377
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Tidskriftsartikel (refereegranskat)abstract
- The bacterium Helicobacter pylori is the causative agent for peptic ulcer disease. Bacterial adherence to the human gastric epithelial lining is mediated by the fucosylated Lewis b (Leb) histo-blood group antigen. The Leb-binding adhesin, BabA, was purified by receptor activity-directed affinity tagging. The bacterial Leb-binding phenotype was associated with the presence of the cag pathogenicity island among clinical isolates of H. pylori. A vaccine strategy based on the BabA adhesin might serve as a means to target the virulent type I strains of H. pylori.
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18. |
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19. |
- Ilver, L, et al.
(författare)
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Quantum size effects in epitaxial ErAs on GaAs(001)
- 1996
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 77:24, s. 4946-4949
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of very thin epitaxial ErAs layers on GaAs(100) is studied with angle resolved photoelectron spectroscopy. Clear evidence is found for confinement induced quantization of states around the Fermi level. From the dispersive properties of the quantum well states effective masses are obtained, representing electron motion parallel to the surface layers and orthogonal to the layers. We find, for the first time, that effective masses along equivalent bulk directions (XW) are significantly different in the thin layers. Furthermore, the bottom of the highest occupied band shifts towards the Fermi level when going from very thin to thick ErAs layers.
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20. |
- Mathieu, R., Svedlindh, P., Sadowski, J., Swiatek, K., Karlsteen, M., Kanski, J., Ilver, L.
(författare)
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Ferromagnetism and interlayer exchange coupling in short period (Ga,Mn)As/GaAs superlattices
- 2002
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Ingår i: Appl. Phys. Lett. 81, 3013.
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Tidskriftsartikel (refereegranskat)
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21. |
- OLSSON, LO, et al.
(författare)
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ANOMALOUS QUENCHING OF PHOTOEMISSION FROM BULK STATES BY DEPOSITION OF CS ON INAS(100)
- 1995
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 52:3, s. 1470-1473
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Tidskriftsartikel (refereegranskat)abstract
- The effect of angle-resolved valence-hand photoelectron spectra from adsorption of small amounts of Cs on InAs(100)4 X 2 has been studied. It is shown that a bulk interband transition is totally quenched at a coverage of Cs that leaves the 4 X 2 reconstruction practically intact. The surface order was monitored by low-energy electron diffraction and photoemission from surface states. A shift of the surface Fermi level to well above the conduction-band minimum is also observed. It is proposed that the resulting development of a two-dimensional electron gas at the surface affects the bulk states probed in photoemission.
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22. |
- OLSSON, LO, et al.
(författare)
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SURFACE ELECTRONIC-STRUCTURE OF INSB(100)4X1 STUDIED BY ANGLE-RESOLVED PHOTOELECTRON-SPECTROSCOPY
- 1995
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 331, s. 1176-1180
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Tidskriftsartikel (refereegranskat)abstract
- The surface electronic structure of the In-rich InSb(100)4 X 1 surface has been studied by angle-resolved photoelectron spectroscopy. To determine the origin of different contributions in spectra, direct bulk interband transitions were first identified using a semi-empirical band structure calculation and assuming direct transitions into free electron-like final bands. Three surface-induced features were identified and their dispersions have been mapped along symmetry directions of the surface Brillouin zone.
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23. |
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24. |
- Roche, Niamh, 1969, et al.
(författare)
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Human gastric glycosphingolipids recognized by Helicobacter pylori vacuolating cytotoxin VacA.
- 2007
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Ingår i: Microbes and infection / Institut Pasteur. - : Elsevier BV. - 1286-4579. ; 9:5, s. 605-14
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Tidskriftsartikel (refereegranskat)abstract
- Many bacterial toxins utilize cell surface glycoconjugate receptors for attachment to target cells. In the present study the potential carbohydrate binding of Helicobacter pylori vacuolating cytotoxin VacA was investigated by binding to human gastric glycosphingolipids on thin-layer chromatograms. Thereby a distinct binding of the toxin to two compounds in the non-acid glycosphingolipid fraction was detected. The VacA-binding glycosphingolipids were isolated and characterized by mass spectrometry and proton NMR as galactosylceramide (Galbeta1Cer) and galabiosylceramide (Galalpha4Galbeta1Cer). Comparison of the binding preferences of the protein to reference glycosphingolipids from other sources showed an additional recognition of glucosylceramide (Glcbeta1Cer), lactosylceramide (Galbeta4Glcbeta1Cer) and globotriaosylceramide (Galalpha4Galbeta4Glcbeta1Cer). No binding to the glycosphingolipids recognized by the VacA holotoxin was obtained with a mutant toxin with deletion of the 37 kDa fragment of VacA (P58 molecule). Collectively our data show that the VacA cytotoxin is a glycosphingolipid binding protein, where the 37 kDa moiety is required for carbohydrate recognition. The ability to bind to short chain glycosphingolipids will position the toxin close to the cell membrane, which may facilitate toxin internalization.
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25. |
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