| 1. |
- Öhlander, Björn, et al.
(författare)
-
Delineation and character of the Archaean-Proterozoic boundary in northern Sweden
- 1993
-
Ingår i: Precambrian Research. - 0301-9268 .- 1872-7433. ; 64:1-4, s. 67-84
-
Tidskriftsartikel (refereegranskat)abstract
- Before the deposition of a Proterozoic cover and the repeated Proterozoic reworking of the older rocks, the presently exposed Archaean areas in northern Sweden formed part of a coherent craton. In the present study, we have used Sm---Nd isotopic analyses of Proterozoic granitoids and metavolcanics to delineate the Archaean palaeoboundary. In a regional context, the transition from strongly negative εNd(t) values in the northeast to positive values in the southwest is distinct, and approximately defines the border of the old craton. The Archaean palaeoboundary extends in a WNW direction, and is subparallel to the longitudinal axis of the Skellefte sulphide ore district but it is situated ≈ 100 km farther to the north. The ≈ 1.9 Ga old granitoids on the two sides of the palaeoboundary were all formed in compressional environments, but those situated to the north have higher contents of LILE and LREE at similar contents of Si. This indicates that they were generated in an area with thicker crust and supports the location of the Archaean-Proterozoic palaeoboundary. There is no simple correlation between the Archaean palaeoboundary, as defined by the isotopic results, and any of the major fracture systems as interpreted from regional geophysical measurements. Reflection seismic work indicates that juvenile volcanic-arc terrains to the south have been thrust onto the Archaean craton. Possible thrust faults have been identified from aeromagnetic measurements. Rifting of the Archaean craton created a passive margin ≈ 2.0 Ga ago. Spreading shifted to convergence with subduction beneath the Archaean continent ≈ 1.9 Ga ago. Subsequently, the resulting juvenile volcanic arc collided with the old continent, and the Archaean palaeoboundary as existing today was formed by a collision characterized by overthrusting. The boundary then was disturbed by later deformation predominantly along NNE-trending fracture systems.
|
|
| 2. |
- Dahlgren, MAG, et al.
(författare)
-
Salt effects on the interaction between adsorbed cationic polyelectrolyte layers - Theory and experiment
- 1993
-
Ingår i: Journal of Physical Chemistry A. - 1089-5639 .- 1520-5215. ; 97, s. 11769-11775
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of inert salt concentration on polyelectrolyte adsorption from aqueous solutions onto oppositely charged surfaces, and the interactions between such surfaces were studied experimentally using a surface force technique and compared to theoretical predictions from Monte Carlo simulations. At a polyelectrolyte concentration of 10 ppm and a low inert salt concentration (10-4 M) the polyelectrolytes adsorb in a flat conformation and the force acting between the surfaces is close to zero down to a separation of 10-15 nm, where the surfaces jump inwards. The attractive force observed at separations below 10 nm is stronger than the expected van der Waals force. The magnitude and range of the attraction agrees with forces obtained from Monte Carlo simulation and we interpret the attraction as being due to bridging polyelectrolytes. When the salt concentration is increased, additional polyelectrolyte adsorption takes place. This gives again rise to a repulsive force, which is significantly larger than what is observed between bare surfaces. The extra repulsion is due to adsorbed polyelectrolytes stretching out from the surfaces and is also predicted from simulations.
|
|
| 3. |
- Welsh, M, et al.
(författare)
-
Shb is a ubiquitously expressed Src homology 2 protein.
- 1994
-
Ingår i: Oncogene. - 0950-9232 .- 1476-5594. ; 9:1, s. 19-27
-
Tidskriftsartikel (refereegranskat)abstract
- To identify serum-inducible genes in the insulin-producing cell line beta TC-1, a library subtraction screening procedure was performed on serum-deprived (G0) and serum-restimulated (G1) insulin-producing beta TC-1 cells. A cDNA containing a motif with strong homology to Src homology 2 (SH2) domains was found using this procedure and called Shb. The Shb cDNA contains two methionine codons in its N-terminus and thus may code for two proteins of 67 and 56 kDa, each with one SH2 domain in its C-terminus. No other structural similarity to proteins with catalytic activity could be detected, suggesting that Shb is a so called adaptor. Shb contains the proline-rich sequence PPPGPGR between the two proposed initiator methionines which resembles a sequence for binding to Src homology 3 (SH3) domains. A second proline-rich sequence was detected after the second methionine codon. The Shb cDNA hybridized to a similar or identical mRNA of 3.1 kb expressed in mouse brain, liver, kidney, heart, NIH3T3 fibroblasts and beta TC-1 cells. Western blot analysis of the same tissues using an antiserum directed against a synthetic peptide corresponding to a part of the SH2 domain of Shb, revealed reactivity with two proteins of 56 and 67 kDa. In addition, a third reactive component of 40 kDa was detected in most tissues. Transfection and transient expression of the Shb cDNA in COS-1 cells yielded increased expression of the 67, 56 and 40 kDa proteins. Transfection and stable expression of the Shb cDNA in pig aortic endothelial cells showed increased expression primarily of the 67 kDa protein. A fusion protein consisting of the SH2 domain of Shb linked to glutathione S-transferase showed increased binding to glycoproteins of cells stimulated with platelet-derived growth factor (PDGF-BB). Furthermore, the autophosphorylated PDGF beta-receptor but not the autophosphorylated epidermal growth factor (EGF) receptor bound specifically to immobilized fusion protein. It is concluded that Shb is a novel SH2-containing protein with proline-rich domains and therefore probably involved in the signal-transduction of some ligand-activated tyrosine kinase receptors.
|
|
