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21.
Interfacial behavior of selected biologically and technologically relevant ions is studied using molecular dynamics simulations employing polarizable potentials. Propensities of choline, tetraalkylammonium (TAA), and sodium cations, and sulfate and chloride anions for the air/water interface are analyzed by means of density profiles. Affinity of TAA ions for the interface increases with their increasing hydrophobicity. Tetramethylammonium favors bulk solvation, whereas cations with propyl and butyl chains behave as surfactants. The choice of counter-anions has only a weak effect on the behavior of these cations. For choline, sodium, chloride and sulfate, the behavior at the air/water interface was compared to the results of our recent study on the segregation of these ions at protein surfaces. No analogy between these two interfaces in terms of ion segregation is found. 相似文献
22.
Diane E. Handy Edith Lubos Yi Yang John D. Galbraith Neil Kelly Ying-Yi Zhang Jane A. Leopold Joseph Loscalzo 《The Journal of biological chemistry》2009,284(18):11913-11921
Glutathione peroxidase-1 (GPx-1) is a selenocysteine-containing enzyme that
plays a major role in the reductive detoxification of peroxides in cells. In
permanently transfected cells with approximate 2-fold overexpression of GPx-1,
we found that intracellular accumulation of oxidants in response to exogenous
hydrogen peroxide was diminished, as was epidermal growth factor receptor
(EGFR)-mediated Akt activation in response to hydrogen peroxide or EGF
stimulation. Knockdown of GPx-1 augmented EGFR-mediated Akt activation,
whereas overexpression of catalase decreased Akt activation, suggesting that
EGFR signaling is regulated by redox mechanisms. To determine whether
mitochondrial oxidants played a role in these processes, cells were pretreated
with a mitochondrial uncoupler prior to EGF stimulation. Inhibition of
mitochondrial function attenuated EGF-mediated activation of Akt in control
cells but had no additional effect in GPx-1-overexpressing cells, suggesting
that GPx-1 overexpression decreased EGFR signaling by decreasing mitochondrial
oxidants. Consistent with this finding, GPx-1 overexpression decreased global
protein disulfide bond formation, which is dependent on mitochondrially
produced oxidants. GPx-1 overexpression, in permanently transfected or
adenovirus-treated cells, also caused overall mitochondrial dysfunction with a
decrease in mitochondrial potential and a decrease in ATP production. GPx-1
overexpression also decreased EGF- and serum-mediated [3H]thymidine
incorporation, indicating that alterations in GPx-1 can attenuate cell
proliferation. Taken together, these data suggest that GPx-1 can modulate
redox-dependent cellular responses by regulating mitochondrial function.Accumulation of reactive oxygen species
(ROS),2 such as
superoxide anion and hydrogen peroxide, is thought to contribute to cellular
damage, apoptosis, and cell death
(1–3);
however, ROS production is part of normal cellular metabolism, and evidence is
accumulating that hydrogen peroxide, in particular, may function as a
signaling molecule necessary for cell growth and survival
(4–8).
Superoxide is generated as a byproduct of mitochondrial respiration and by
cellular redox enzymes, such as NADPH oxidase, that are stimulated through
receptor-mediated mechanisms
(9). Hydrogen peroxide is
formed from the dismutation of superoxide, which occurs spontaneously or can
be catalyzed by superoxide dismutase
(10) or, alternatively, is
produced by the two-electron enzymatic reduction of molecular oxygen by
various oxidases, such as xanthine oxidase
(11). Recent studies also
suggest that hydrogen peroxide may be directly generated by receptor-ligand
interactions (12). One
mechanism by which hydrogen peroxide may modulate signal transduction is
through the reversible oxidation of proteins at redox-active cysteines,
including, for example, thiols in tyrosine kinase phosphatases. Oxidation and
inactivation of phosphatases, such as PTEN, have been shown to promote the
activity of the pro-growth and -survival kinase, Akt
(13).Antioxidant enzymes, such as glutathione peroxidase, catalase, and
peroxiredoxins, serve to eliminate hydrogen peroxide, thereby regulating
cellular responses to this endogenous oxidant. GPx-1 is a selenoprotein and
one of a family of peroxidases that reductively inactivate peroxides using
glutathione as a source of reducing equivalents
(14,
15). GPx-1, in particular, is
a major intracellular antioxidant enzyme that is found in the cytoplasm and
mitochondria of all cell types. In cell culture models as well as in genetic
mouse models, GPx-1 overexpression is associated with enhanced protection
against oxidative stress
(16–19);
however, GPx-1-overexpressing mice can become obese and insulin-resistant, and
have attenuated insulin-mediated activation of Akt
(20). Thus, to study how GPx-1
modulates the effects of cellular oxidants on cell signaling and cell growth,
we analyzed cellular responses to hydrogen peroxide and EGF in permanently
transfected cells overexpressing GPx-1. 相似文献
23.
Lubos Halada Doug Evans Carlos Romão Jan-Erik Petersen 《Biodiversity and Conservation》2011,20(11):2365-2378
The aim of this paper is to identify the habitat types listed in the Habitats Directive Annex I that require low-intensity
agricultural management for their existence. We assessed the link between the Annex I habitat types and agricultural practices
in order to identify habitat types that depend on the continuation of agricultural practices or whose existence is prolonged
or spatially enlarged via blocking or reducing the secondary succession by agricultural activities. 63 habitat types that
depend on or which can profit from agricultural activities—mainly grazing and mowing—were identified. They are classified
into 2 groups: (1) habitats fully dependent on the continuation of agricultural management; (2) habitats partly dependent
on the continuation of agricultural management. This paper also briefly discusses habitat types for which either doubts remain
on their dependence on agricultural management, or the relation to extensive farming practices exists only in part of their
area of distribution in Europe or under certain site conditions, respectively. Assessments of the conservation status of habitats
of European Importance by 25 EU Member States in 2007 showed that habitats identified by us as depending on agricultural practices
had a worse status than non-agricultural habitats. 相似文献
24.
Chrenek P Ryban L Vetr H Makarevich AV Uhrin P Paleyanda RK Binder BR 《Transgenic research》2007,16(3):353-361
Transgenic founder rabbits carrying a gene construct consisting of a 2.5 kb murine whey acidic protein promoter (mWAP), 7.2 kb
of the human clotting factor VIII (hFVIII) cDNA and 4.6 kb of 3′ flanking sequences of mWAP gene were crossed for three generations.
All transgenic animals showed stable transgene transmission. Transgenic females showed high level of recombinant hFVIII (rhFVIII)
mRNA expression in biopsed mammary gland tissues, while marginal expression of rhFVIII mRNA was observed in the spleen, lung
and brain. No adverse effects of ectopic expression on the physiology of the rabbits were observed. Expression was not detected
in the liver, kidney, heart and skeletal muscle. In transgenic females derived from three generations, rhFVIII protein was
secreted from the mammary gland of lactating females, as shown by Western blotting. Biological activity of rhFVIII protein,
as revealed in clotting assays was ranged from 0.012 to 0.599 IU/ml corresponding to 1.2% and 59.9% of the hFVIII level in
normal human plasma. No apparent effect of secreted rhFVIII on the milk performance of rabbits was observed. Our results confirm
the possibility of producing a significant amount of a biologically active rhFVIII in the mammary gland of established transgenic
rabbit lines. 相似文献
25.
Lubos Cipak Randy Hyppa Gerald Smith Juraj Gregan 《Cell cycle (Georgetown, Tex.)》2012,11(8):1626-1633
To study meiosis, synchronous cultures are often indispensable, especially for physical analyses of DNA and proteins. A temperature-sensitive allele of the Pat1 protein kinase (pat1-114) has been widely used to induce synchronous meiosis in the fission yeast Schizosaccharomyces pombe, but pat1-114-induced meiosis differs from wild-type meiosis, and some of these abnormalities might be due to higher temperature needed to inactivate the Pat1 kinase. Here, we report an ATP analog-sensitive allele of Pat1 [Pat1(L95A), designated pat1-as2] that can be used to generate synchronous meiotic cultures at physiological temperature. In pat1-as2 meiosis, chromosomes segregate with higher fidelity, and spore viability is higher than in pat1-114 meiosis, although recombination is lower by a factor of 2–3 in these mutants than in starvation-induced pat1+ meiosis. Addition of the mat-Pc gene improved chromosome segregation and spore viability to nearly the level of starvation-induced meiosis. We conclude that pat1-as2
mat-Pc cells offer synchronous meiosis with most tested properties similar to those of wild-type meiosis. 相似文献
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