University of Dundee

About: University of Dundee is a education organization based out in Dundee, United Kingdom. It is known for research contribution in the topics: Population & Protein kinase A. The organization has 19258 authors who have published 39640 publications receiving 1919433 citations. The organization is also known as: Universitas Dundensis & Dundee University.

Specific binding of the Akt-1 protein kinase to phosphatidylinositol 3,4,5-trisphosphate without subsequent activation

Abstract: Recent evidence has suggested that activation of phosphoinositide 3-kinase (PI 3-kinase) is required for the activation of Akt-1 by growth factors and insulin. Here we demonstrate by two independent methods that Akt-1 from L6 myotubes binds to PtdIns(3,4,5)P3, PtdIns(3,4)P2 and PtdIns(4,5)P2 when presented against a background of phosphatidylserine (PtdSer) or a 1:1 mixture of PtdSer and phosphatidylcholine (PtdCho). No binding was observed with the lipids PtdIns(3,5)P2, PtdIns4P and PtdIns3P or background lipids. Activated, hyperphosphorylated forms of Akt-1 from insulin-stimulated L6 myotubes bound to PtdIns(3,4,5)P3 in a similar manner as inactive Akt-1. Quantitative analysis using surface plasmon resonance showed that the equilibrium association constant for the binding of Akt-1 to PtdIns(3,4,5)P3 was submicromolar and that PtdIns(3,4)P2 and PtdIns(4,5)P2 bound to Akt-1 with 3- and 6-fold lower affinities respectively. Interaction of Akt-1 with PtdIns(3,4,5)P3 did not activate the protein kinase activity, either before or after incubation with MgATP. A model is presented in which PtdIns(3,4,5)P3 may prime Akt-1 for activation by another protein kinase, perhaps by recruiting it to the plasma membrane.

Investigation of the density of localized states in a-Si using the field effect technique

Abstract: The electronic properties of amorphous solids are largely determined by the distribution of localized states N (ϵ) in the mobility gap. In this paper, the field effect technique is applied to the experimental study of N (ϵ) in specimens of a-Si prepared by the glow discharge method and by vacuum evaporation. The experimental approach and the analysis of the results are discussed in some detail. N (ϵ) curves, extending over an energy range of up to 0.5 eV have been obtained for a series of glow discharge specimens, deposited at substrate temperatures between 310 and 570 K. The results show structure in the gap states, a well-defined minimum almost in the centre of the mobility gap and a rapid rise in N (ϵ), 0.18 eV below ϵ c , which is identified with the onset of band tail states. The field effect data confirm that the predominant conduction mechanism at room temperature changes from hole hopping to transport in extended electron states, as the Fermi level is moved through the minimum in N (ϵ) The effects of annealing on the state distribution have been investigated, showing that N ( ϵ f ) can be reduced by one or two orders of magnitude. The nature of the gap states is discussed and the divacancy is suggested as a basic model for the electronic states involved.