| 1. |
- Tatarkhanov, M., et al.
(författare)
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The structure of mixed H2O-OH monolayer films on Ru(0001)
- 2008
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 129:15, s. 154109-
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Tidskriftsartikel (refereegranskat)abstract
- Scanning tunneling microscopy (STM) and x-ray absorption spectroscopy (XAS) have been used to study the structures produced by water on Ru(0001) at temperatures above 140 K. It was found that while undissociated water layers are metastable below 140 K, heating above this temperature produces drastic transformations, whereby a fraction of the water molecules partially dissociate and form mixed H2O-OH structures. X-ray photoelectron spectroscopy and XAS revealed the presence of hydroxyl groups with their O-H bond essentially parallel to the surface. STM images show that the mixed H2O-OH structures consist of long narrow stripes aligned with the three crystallographic directions perpendicular to the close-packed atomic rows of the Ru(0001) substrate. The internal structure of the stripes is a honeycomb network of H-bonded water and hydroxyl species. We found that the metastable low temperature molecular phase can also be converted to a mixed H2O-OH phase through excitation by the tunneling electrons when their energy is 0.5 eV or higher above the Fermi level. Structural models based on the STM images were used for density functional theory optimizations of the stripe geometry. The optimized geometry was then utilized to calculate STM images for comparison with the experiment.
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| 2. |
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| 3. |
- Clark, M., et al.
(författare)
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Revealing the secrets of dormancy and of survival during desiccation
- 2007
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Ingår i: Comparative Biochemistry and Physiology a-Molecular & Integrative Physiology. - : Elsevier BV. - 1095-6433 .- 1531-4332. ; 146:4
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Konferensbidrag (refereegranskat)abstract
- Dormancy is a strategy used by many organisms to survive adverse conditions. We aim at enhancing our knowledge of dormancy so as to assess the feasibility of inducing cells or organisms into reversible dormant stages or survival during desiccating conditions. Genomic, proteomic and metabolomic tools used in the course of our studies aim at identifying the molecular and cellular processes that enable five model organisms to tolerate adverse conditions. These are: Cyanobacteria that have specialized dormant cells (akinetes) that tolerate unfavourable environmental conditions Baker's yeast that can survive long periods in a spore phase, that are characterized by desiccation and high levels of trehalose Rotifers that produce eggs (resting eggs) containing developmental-arrested embryos after sexual (but not asexual) reproduction Arctic springtails that reduce their body water content to avoid freezing while producing trehalose and becoming metabolically inactive Killifish embryos in eggs that show resistance to environmental desiccation conditions Our studies aim at revealing the mechanisms that establish dormancy and resistance to desiccation, those that allow the revival from dormant stages and the properties that make dormant stages stress-tolerant. The search for common denominators will assist in leading potentially useful strategies for artificial induction of dormancy and of cell preservation.
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| 4. |
- Schiöth, Helgi B, et al.
(författare)
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Evolutionary conservation of the structural, pharmacological, and genomic characteristics of the melanocortin receptor subtypes
- 2005
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Ingår i: Peptides. - : Elsevier BV. - 0196-9781 .- 1873-5169. ; 26:10, s. 1886-1900
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Tidskriftsartikel (refereegranskat)abstract
- We have cloned melanocortin receptors (MCRs) from several species of fish. The MC4R and MC5R subtypes arose early in vertebrate evolution and their primary structure is remarkably conserved. Expression and pharmacological characterization of the MCRs in fish has revealed that they bind and respond to melanocortin peptides with high potency. Detailed characterization of the binding properties of the different subtypes suggests that MCRs in early vertebrates had preference for adrenocorticotropic hormone (ACTH) peptides, while the high sensitivity for the shorter proopiomelanocortin (POMC) products, such as the α-, β-, and γ-melanocyte-stimulating hormone (MSH), has appeared later, perhaps as the MCR subtypes gained more specialized functions. The MCR repertoire shows in general high similarities in their primary structures, while they are however not similar in terms of functional roles. The MCRs serve therefore as an interesting model family to understand the molecular mechanisms of how functions of the genes can diverge during evolution. In this review, we provide an overview of our recent studies on the cloning, expression, pharmacology, 3D modeling, and genomic studies of the MCRs in non-mammalian species.
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