| 1. |
- Yabuta, Hikaru, et al.
(författare)
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Macromolecular organic matter in samples of the asteroid (162173) Ryugu
- 2023
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Ingår i: Science. - : American Association for the Advancement of Science. - 0036-8075 .- 1095-9203. ; 379:6634
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Tidskriftsartikel (refereegranskat)abstract
- Samples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by the Hayabusa2 spacecraft. We investigated the macromolecular organic matter in Ryugu samples and found that it contains aromatic and aliphatic carbon, ketone, and carboxyl functional groups. The spectroscopic features of the organic matter are consistent with those in chemically primitive carbonaceous chondrite meteorites that experienced parent-body aqueous alteration (reactions with liquid water). The morphology of the organic carbon includes nanoglobules and diffuse carbon associated with phyllosilicate and carbonate minerals. Deuterium and/or nitrogen-15 enrichments indicate that the organic matter formed in a cold molecular cloud or the presolar nebula. The diversity of the organic matter indicates variable levels of aqueous alteration on Ryugus parent body.
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| 2. |
- Andersson, Ove, et al.
(författare)
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Thermal conductivity of amorphous ices
- 2002
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969 .- 0163-1829 .- 1095-3795. ; 65:14
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivities κ of high-density amorphous (HDA) ice and low-density amorphous (LDA) ice were measured under pressure. The results for HDA show typical glasslike behavior, i.e., positive dκ/dT, whereas LDA exhibits crystal-like behavior, indicating that phonon-phonon scattering is dominant. LDA appears to be unique among apparently topologically disordered glasses to exhibit such behavior. Moreover, the results imply that LDA and glassy water formed by rapid cooling are different states.
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| 3. |
- Brate, Jon, et al.
(författare)
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Unicellular Origin of the Animal MicroRNA Machinery
- 2018
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 28:20, s. 3288-
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Tidskriftsartikel (refereegranskat)abstract
- The emergence of multicellular animals was associated with an increase in phenotypic complexity and with the acquisition of spatial cell differentiation and embryonic development. Paradoxically, this phenotypic transition was not paralleled by major changes in the underlying developmental toolkit and regulatory networks. In fact, most of these systems are ancient, established already in the unicellular ancestors of animals [1-5]. In contrast, the Microprocessor protein machinery, which is essential for microRNA (miRNA) biogenesis in animals, as well as the miRNA genes themselves produced by this Microprocessor, have not been identified outside of the animal kingdom [6]. Hence, the Microprocessor, with the key proteins Pasha and Drosha, is regarded as an animal innovation [7-9]. Here, we challenge this evolutionary scenario by investigating unicellular sister lineages of animals through genomic and transcriptomic analyses. We identify in Ichthyosporea both Drosha and Pasha (DGCR8 in vertebrates), indicating that the Microprocessor complex evolved long before the last common ancestor of animals, consistent with a pre-metazoan origin of most of the animal developmental gene elements. Through small RNA sequencing, we also discovered expressed bona fide miRNA genes in several species of the ichthyosporeans harboring the Microprocessor. A deep, pre-metazoan origin of the Microprocessor and miRNAs comply with a view that the origin of multicellular animals was not directly linked to the innovation of these key regulatory components.
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| 4. |
- Gentekaki, Eleni, et al.
(författare)
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Extreme genome diversity in the hyper-prevalent parasitic eukaryote Blastocystis
- 2017
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Ingår i: PLoS biology. - : PUBLIC LIBRARY SCIENCE. - 1544-9173 .- 1545-7885. ; 15:9
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Tidskriftsartikel (refereegranskat)abstract
- Blastocystis is the most prevalent eukaryotic microbe colonizing the human gut, infecting approximately 1 billion individuals worldwide. Although Blastocystis has been linked to intestinal disorders, its pathogenicity remains controversial because most carriers are asymptomatic. Here, the genome sequence of Blastocystis subtype (ST) 1 is presented and compared to previously published sequences for ST4 and ST7. Despite a conserved core of genes, there is unexpected diversity between these STs in terms of their genome sizes, guanine-cytosine (GC) content, intron numbers, and gene content. ST1 has 6,544 protein-coding genes, which is several hundred more than reported for ST4 and ST7. The percentage of proteins unique to each ST ranges from 6.2% to 20.5%, greatly exceeding the differences observed within parasite genera. Orthologous proteins also display extreme divergence in amino acid sequence identity between STs (i.e., 59%-61% median identity), on par with observations of the most distantly related species pairs of parasite genera. The STs also display substantial variation in gene family distributions and sizes, especially for protein kinase and protease gene families, which could reflect differences in virulence. It remains to be seen to what extent these inter-ST differences persist at the intra-ST level. A full 26% of genes in ST1 have stop codons that are created on the mRNA level by a novel polyadenylation mechanism found only in Blastocystis. Reconstructions of pathways and organellar systems revealed that ST1 has a relatively complete membrane-trafficking system and a near-complete meiotic toolkit, possibly indicating a sexual cycle. Unlike some intestinal protistan parasites, Blastocystis ST1 has near-complete de novo pyrimidine, purine, and thiamine biosynthesis pathways and is unique amongst studied stramenopiles in being able to metabolize alpha-glucans rather than beta-glucans. It lacks all genes encoding heme-containing cytochrome P450 proteins. Predictions of the mitochondrion-related organelle (MRO) proteome reveal an expanded repertoire of functions, including lipid, cofactor, and vitamin biosynthesis, as well as proteins that may be involved in regulating mitochondrial morphology and MRO/endoplasmic reticulum (ER) interactions. In sharp contrast, genes for peroxisome-associated functions are absent, suggesting Blastocystis STs lack this organelle. Overall, this study provides an important window into the biology of Blastocystis, showcasing significant differences between STs that can guide future experimental investigations into differences in their virulence and clarifying the roles of these organisms in gut health and disease.
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| 5. |
- Nagahama, Maki, et al.
(författare)
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Formation of molecular alloys by solid-state vitrification
- 2000
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Ingår i: Thermochimica Acta. - : Elsevier. - 0040-6031 .- 1872-762X. ; 363:1-2, s. 165-174
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Tidskriftsartikel (refereegranskat)abstract
- Formation of a vitreous molecular alloy was observed when a mixture of deoxycholic acid (DCA) and tri-O-methyl-beta -cyclodextrin (TMCD) crystals was subjected to mechanical milling at room temperature. Only a single glass transition temperature Tg, varying with the composition, was observed by DSC. This means that the vitreous state exhibits a single relaxation process as a whole by forming a molecular alloy. The Tg showed a maximum value at the equimolar composition, indicating a strong interaction between the two components. A study of the phase diagram clarified the existence of intermolecular compounds between them. Thermal conductivity of the milled solid of equimolar mixture exhibited a temperature dependence characteristic of glassy materials. p-Terphenyl and tris(hydroxymethyl)aminomethane crystals could not be vitrified. When each of them was milled with DCA or TMCD, vitreous molecular alloys were obtained in a limited composition range. These alloys exhibited also a single Tg and underwent a phase separation on devitrification. Formation of molecular alloys was discussed based on the nature of disorder of the system.
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