| 1. |
- Mårtensson, Annica, et al.
(författare)
-
PEBP2 and c-myb sites crucial for lambda5 core enhancer activity in pre-B cells.
- 2001
-
Ingår i: European Journal of Immunology. - 0014-2980 .- 1521-4141. ; 31:11, s. 3165-3174
-
Tidskriftsartikel (refereegranskat)abstract
- The lambda5 gene is expressed exclusively in precursor (pre-) B cells where its gene product, as part of the pre-B cell receptor, is crucial for the proliferation of these cells. Several DNA regions regulate the activity and expression pattern of the lambda5 gene. Amongst these is an enhancer, B(lambda5), located 5' of the gene. Here we analyze the lambda5 enhancer core, b(lambda5), which in earlier experiments was demonstrated to retain 50% of the enhancer activity, and show that this activity is restricted to pre-B cells. We identify a DNA element within b(lambda5), PEBP2(lambda5), which is essential for enhancer activity: mutation within this site dramatically reduces core enhancer activity in pre-B cells. The PEBP2(lambda5) site binds bacterially produced polyoma enhancer binding proteins (PEBP) (Runx/AML/CBFA). Furthermore, PEBP2 proteins present in nuclear extracts from murine pre-B cells bind to the PEBP2(lambda5) element. PEBP2 proteins in mature B cells also bind to the PEBP2(lambda5 )element, implying that if PEBP2 proteins are responsible for the stage-specific expression, they have to be non-activating or inhibiting in mature B cells. We also demonstrate that a described partner of PEBP2, c-myb, binds to a sequence termed myb(lambda5) located just upstream of the PEBP2(lambda5) site in the core enhancer. The myb(lambda5) element is also crucial for enhancer activity, since mutating the myb site reduces core enhancer activity to the same extent as mutating the PEBP2 site. Earlier reports have shown that c-myb is expressed at high levels in pre-B cell lines whereas its expression is down-regulated in more mature B cell lines. Thus, c-myb may be involved in determining the stage-specific expression of the lambda5 gene.
|
|
| 2. |
- Andreasson, Joakim, 1973, et al.
(författare)
-
Photoinduced hole transfer from the triplet state in a porphyrin-based donor-bridge-acceptor system
- 2003
-
Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 107:42, s. 8825-8833
-
Tidskriftsartikel (refereegranskat)abstract
- The triplet excited-state deactivation of a gold porphyrin (AuP) in porphyrin-based donor-bridge-acceptor (D-B-A) systems has been studied. The results from room temperature and 80 K measurements are presented. The primary objectives have been to investigate whether electrons/electron holes or excitation energy could be transferred from (AuP)-Au-3 to the appended zinc porphyrin (ZnP) in the dimers. As the bridging chromophores in our D-B-A systems separate the ZnP and AuP moieties by 19 A edge-to-edge, we do not expect a significant contribution to either electron or energy transfer from a direct (through space) exchange mechanism. This gives us the opportunity to scrutinize how the bridging chromophores influence the transfer reactions. The results show that quenching of (AuP)-Au-3 occurs with high efficiency in the dimers that are connected by fully conjugated bridging chromophores, whereas no quenching is observed when the conjugation of the bridge is broken. We also observed that the decay of (AuP)-Au-3 is complex at temperatures below 110 K. In addition to the two previously published lifetimes on the order of some 10-100 mus, we have found a third lifetime on the nanosecond time scale.
|
|
| 3. |
- Carlberg, Patrick, et al.
(författare)
-
Nanoimprint - a tool for realizing nano-bio research
- 2004
-
Ingår i: 2004 4th IEEE Conference on Nanotechnology. - 0780385365 ; , s. 199-200
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we present a status report on how implementation of nanoimprint lithography has advanced our research. Contact guidance nerve growth experiments have so far primarily been done on micrometer-structured surfaces. We have made a stamp with 17 areas of different, submicron, line width and spacing covering a total 2.6 mm
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Dick Thelander, Kimberly, et al.
(författare)
-
Growth of GaP nanotree structures by sequential seeding of 1D nanowires
- 2004
-
Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 272:1-4, s. 131-137
-
Tidskriftsartikel (refereegranskat)abstract
- Complex nanostructures are becoming increasingly important for the development of nanoscale devices and functional nanomaterials. Precise control of size and morphology of these structures is critical to their fabrication and exploitation. We have developed a method for stepwise growth of tree-like nanostructures via the vapour liquid-solid (VLS) growth mode, demonstrated for III-V semiconductor materials. This method uses the initial seeding of nanowires by catalytic aerosol nanoparticles to form the trunk, followed by sequential seeding of branching structures. Here we present a detailed study of the growth of these complex structures using Gap. Diameter of each level of nanowires is directly determined by seed particle diameters, and number of branches is determined by seed particle density. Growth rate is shown to increase with temperature to a maximum corresponding to the temperature of complete decomposition of the Group-III precursor material, and subsequently decrease due to competition with bulk growth. Growth rate also depends on flow of the Group-III precursor, but not on the Group-V precursor. Finally, there is a relationship between the number of branches and their growth rate, suggesting that material diffusion plays a role in nanowire branch growth. (C) 2004 Elsevier B.V. All rights reserved.
|
|
| 7. |
- Dick Thelander, Kimberly, et al.
(författare)
-
Synthesis of branched 'nanotrees' by controlled seeding of multiple branching events
- 2004
-
Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 3:6, s. 380-384
-
Tidskriftsartikel (refereegranskat)abstract
- The formation of nanostructures with controlled size and morphology has been the focus of intensive research in recent years(1-10). Such nanostructures are important in the development of nanoscale devices and in the exploitation of the properties of nanomaterials(9). Here we show how tree-like nanostructures ('nanotrees') can be formed in a highly controlled way. The process involves the self-assembled growth of semiconductor nanowires via the vapour-liquid-solid(11) growth mode. This bottom-up method uses initial seeding by catalytic nanoparticles(12) to form the trunk, followed by the sequential seeding of branching structures. Each level of branching is controlled in terms of branch length, diameter and number, as well as chemical composition. We show, by high-resolution transmission electron microscopy, that the branching mechanism gives continuous crystalline (monolithic) structures throughout the extended and complex tree-like structures. The controlled seeding method that we report here has potential as a generic means of forming complex branching structures, and may also offer opportunities for applications, such as the mimicking of photosynthesis in nanotrees.
|
|
| 8. |
|
|
| 9. |
- Mårtensson, Thomas, et al.
(författare)
-
Epitaxial III-V nanowires on silicon
- 2004
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 4:10, s. 1987-1990
-
Tidskriftsartikel (refereegranskat)abstract
- We present results of ideal epitaxial nucleation and growth of III-V semiconductor nanowires on silicon substrates. This addresses the long-time challenge of integrating high performance III-V semiconductors with mainstream Si technology. Efficient room-temperature generation of light on silicon is demonstrated by the incorporation of double heterostructure segments in such nanowires. We expect that advanced heterostructure devices, such as resonant tunneling diodes, superiattice device structures, and heterostructure photonic devices for on-chip communication, could now become available as complementary device technologies for integration with silicon.
|
|
| 10. |
- Mårtensson, Thomas, et al.
(författare)
-
Fabrication of individually seeded nanowire arrays by vapour-liquid-solid growth
- 2003
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 14:12, s. 1255-1258
-
Tidskriftsartikel (refereegranskat)abstract
- We report on a method of synthesizing arrays of individually seeded nanowires. An electron beam lithography and metal lift-off method was used to pattern InP(111)B substrates with catalysing gold particles. Vertical InP(111)B nanowire arrays were then grown from the gold particles, using metal-organic vapour phase epitaxy. The lithographic nature of the method allows individual control over each nanowire. Possible applications for such deterministic and uniform arrays include producing arrays of nanowire devices, two-dimensional photonic band gap structures and field emission displays, amongst others.
|
|
