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Carbon Source Dependent Dynamics of the Ccr4-Not Complex in Saccharomyces cerevisiae
Joakim Norbeck 한국미생물학회 2008 The journal of microbiology Vol.46 No.6
We have investigated the composition of the conserved Ccr4-Not complex during different physiological states of Saccharomyces cerevisiae. Major changes were found, most notably in the expression of the central scaffold protein Not1p, which was strongly reduced in the absence of glucose. The low expression of Not1p was also evident from the inability of Pop2p to co-purify Not1p in cells from cultures lacking glucose. However, Not1p was still essential under conditions of low expression. The downregulation of Not1p indicates that many of the Ccr4-Not complex components are likely to have roles outside of the complex. We suggest that the use of different carbon sources will be a good starting point to unravel these functions.
The importance of windows of opportunity for foreign policy change
Fredrik Doeser,Joakim Eidenfalk 한국외국어대학교 국제지역연구센터 2013 International Area Studies Review Vol.16 No.4
This article emphasizes how individual decision-makers and their perceptions of windows of opportunity can play a decisive role for major changes in the foreign policy of states by conducting two case studies. The first case is the change that occurred in Denmark’s foreign policy in August 1990 when its government dispatched a warship to the Persian Gulf to participate in the monitoring of the United Nations sanctions against Iraq. The second case is the change that occurred in Australia’s foreign policy in April–May 2003 when its government abandoned Australia’s long-standing “hands-off” approach toward Solomon Islands by leading a multinational military intervention. The article demonstrates that individual decision-makers, with a longstanding desire to change policy, perceived structural changes as a window of opportunity for initiating the desired policy changes. The article concludes that, had it not been for these particular individuals, and their perceptions of the world around them, events would most likely have unfolded in a different way.
Nina Johansson,Karl O. Persson,Joakim Norbeck,Christer Larsson 한국생물공학회 2017 Biotechnology and Bioprocess Engineering Vol.22 No.2
Ethylene is a major petrochemical for which biotechnological production methods are an attractive alternative. Here we use a system based on a bacterial ethylene forming enzyme (EFE) expressed in Saccharomyces cerevisiae. Metabolic modelling performed in a previous study identified re-oxidation of NADH as a factor limiting ethylene production in S. cerevisiae. In line with this, we here found that strains with multicopy plasmid expression of the heterologous oxidases nox and Aox1 led to significantly increased specific ethylene productivity, up 12 and 36%, respectively, compared to the control strain with empty plasmid. However the productivity and yield was only improved in the AOX expressing strain compared to that of the control strain. Both oxidase expressing strains also exhibited increased respiration rates compared to the reference strain, with specific oxygen consumption rates being roughly doubled in both strains. The AOX strain furthermore exhibited a significant increase in the EFE substrate 2-oxoglutarate formation compared to the reference strain, linking an improvement in ethylene production to both increased respiratory capacity and increased substrate availability, thereby corroborating our previous finding.
Kimm, Taysun,Cen, Renyue,Rosdahl, Joakim,Yi, Sukyoung K. American Astronomical Society 2016 The Astrophysical journal Vol.823 No.1
<P>We investigate the formation of metal-poor globular clusters (GCs) at the center of two dark matter halos with M-halo similar to 4 X 10(7) M-circle dot at z > 10 using cosmological radiation-hydrodynamics simulations. We find that very compact (less than or similar to 1 pc) and massive (similar to 6 X 10(5) M-circle dot.)clusters form rapidly when pristine gas collapses isothermally with the aid of efficient Ly alpha emission during the transition from molecular-cooling halos to atomic-cooling halos. Because the local free-fall time of dense star-forming gas is very short (<< 1 Myr), a large fraction of the collapsed gas is turned into stars before stellar feedback processes blow out the gas and shut down star formation. Although the early stage of star formation is limited to a small region of the central star-forming disk, we find that the disk quickly fragments due to metal enrichment from supernovae. Sub-clusters formed in the fragmented clouds eventually merge with the main cluster at the center. The simulated clusters closely resemble the local GCs in mass and size but show a metallicity spread that is much wider than found in the local GCs. We discuss a role of pre-enrichment by Pop III and II stars as a potential solution to the latter issue. Although not without shortcomings, it is encouraging that a naive blind (not tuned) cosmological simulation presents a possible channel for the formation of at least some massive GCs.</P>