| 1. |
- Hovmöller, Sven, et al.
(författare)
-
Structures of pseudo-decagonal approximants in Al-Co-Ni
- 2012
-
Ingår i: Philosophical Transactions. Series A. - : The Royal Society. - 1364-503X .- 1471-2962. ; 370:1969, s. 2949-2959
-
Tidskriftsartikel (refereegranskat)abstract
- Quasi-crystals shocked the crystallographic world when they were reported in 1984. We now know that they are not a rare exception, and can be found in many alloy systems. One of the richer systems for quasi-crystals and their approximants is Al-Co-Ni. A large series of pseudo-decagonal (PD) approximants have been found. Only two of them, PD4 and PD8, have been solved by X-ray crystallography. We report here the structures of PD1, PD2, PD3 and PD5, solved from the limited information that is provided by electron diffraction patterns, unit cell dimensions and high-resolution electron microscopy images.
|
|
| 2. |
- Ronquist, Fredrik, et al.
(författare)
-
Completing Linnaeus’s inventory of the Swedish insect fauna: only 5,000 species left?
- 2020
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 15:3
-
Tidskriftsartikel (refereegranskat)abstract
- Despite more than 250 years of taxonomic research, we still have only a vague idea about the true size and composition of the faunas and floras of the planet. Many biodiversity inventories provide limited insight because they focus on a small taxonomic subsample or a tiny geographic area. Here, we report on the size and composition of the Swedish insect fauna, thought to represent roughly half of the diversity of multicellular life in one of the largest European countries. Our results are based on more than a decade of data from the Swedish Taxonomy Initiative and its massive inventory of the country’s insect fauna, the Swedish Malaise Trap Project The fauna is considered one of the best known in the world, but the initiative has nevertheless revealed a surprising amount of hidden diversity: more than 3,000 new species (301 new to science) have been documented so far. Here, we use three independent methods to analyze the true size and composition of the fauna at the family or subfamily level: (1) assessments by experts who have been working on the most poorly known groups in the fauna; (2) estimates based on the proportion of new species discovered in the Malaise trap inventory; and (3) extrapolations based on species abundance and incidence data from the inventory. For the last method, we develop a new estimator, the combined non-parametric estimator, which we show is less sensitive to poor coverage of the species pool than other popular estimators. The three methods converge on similar estimates of the size and composition of the fauna, suggesting that it comprises around 33,000 species. Of those, 8,600 (26%) were unknown at the start of the inventory and 5,000 (15%) still await discovery. We analyze the taxonomic and ecological composition of the estimated fauna, and show that most of the new species belong to Hymenoptera and Diptera groups that are decomposers or parasitoids. Thus, current knowledge of the Swedish insect fauna is strongly biased taxonomically and ecologically, and we show that similar but even stronger biases have distorted our understanding of the fauna in the past. We analyze latitudinal gradients in the size and composition of known European insect faunas and show that several of the patterns contradict the Swedish data, presumably due to similar knowledge biases. Addressing these biases is critical in understanding insect biomes and the ecosystem services they provide. Our results emphasize the need to broaden the taxonomic scope of current insect monitoring efforts, a task that is all the more urgent as recent studies indicate a possible worldwide decline in insect faunas.
|
|
| 3. |
|
|
| 4. |
- Almqvist, Jonas, et al.
(författare)
-
Docking and homology modeling explain inhibition of the human vesicular glutamate transporters
- 2007
-
Ingår i: Protein Science. - 0961-8368 .- 1469-896X. ; 16:9, s. 1819-1829
-
Tidskriftsartikel (refereegranskat)abstract
- As membrane transporter proteins, VGLUT1-3 mediate the uptake of glutamate into synaptic vesicles at presynaptic nerve terminals of excitatory neural cells. This function is crucial for exocytosis and the role of glutamate as the major excitatory neurotransmitter in the central nervous system. The three transporters, sharing 76% amino acid sequence identity in humans, are highly homologous but differ in regional expression in the brain. Although little is known regarding their three- dimensional structures, hydropathy analysis on these proteins predicts 12 transmembrane segments connected by loops, a topology similar to other members in the major facilitator superfamily, where VGLUT1-3 have been phylogenetically classified. In this work, we present a three- dimensional model for the human VGLUT1 protein based on its distant bacterial homolog in the same superfamily, the glycerol- 3-phosphate transporter from Escherichia coli. This structural model, stable during molecular dynamics simulations in phospholipid bilayers solvated by water, reveals amino acid residues that face its pore and are likely to affect substrate translocation. Docking of VGLUT1 substrates to this pore localizes two different binding sites, to which inhibitors also bind with an overall trend in binding affinity that is in agreement with previously published experimental data.
|
|
| 5. |
|
|
| 6. |
- Almqvist, Jonas, 1975-
(författare)
-
Structural modeling of membrane transporter proteins
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A fundamental process of all living organisms - the transport of molecules across cellular membranes through membrane transport proteins - is investigated.After a brief review of general properties of biological membranes follows a recollection of the major methods of membrane transport that Nature utilizes (Chapter 1). This is followed by a description of important experimental (Chapter 2) and theoretical methods (Chapter 3) for structural studies of membrane proteins. The findings on membrane protein transport in papers I-IV are then summarized (Chapter 4) and important findings are discussed. The remaining text is a discussion on relevant theoretical and experimental methods.
|
|
| 7. |
|
|
| 8. |
- Corma, Averlino, et al.
(författare)
-
Synthesis and structure of polymorph B of zeolite Beta
- 2008
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 20:9, s. 3218-3223
-
Tidskriftsartikel (refereegranskat)abstract
- It was found that either polymorph B or polymorph C of zeolite beta can be obtained from the same structure directing agent: 4,4-dimethyl-4-azonia-tricyclo[5.2.2.02,6]undec-8-ene hydroxide. The synthesis occurs through a consecutive process where polymorph B is first formed and then transformed into polymorph C. It is possible to produce a zeolite highly enriched in polymorph B, provided that the transformation of this phase into polymorph C is slowed down up to the point where polymorph C is only detected at trace levels. The structure of polymorph B was determined for the first time by electron crystallography with SAED and HRTEM from areas of unfaulted polymorph B crystals.
|
|
| 9. |
- Gemmi, Mauro, et al.
(författare)
-
3D Electron Diffraction : The Nanocrystallography Revolution
- 2019
-
Ingår i: ACS central science. - : American Chemical Society (ACS). - 2374-7943 .- 2374-7951. ; 5:8, s. 1315-1329
-
Tidskriftsartikel (refereegranskat)abstract
- Crystallography of nanocrystalline materials has witnessed a true revolution in the past 10 years, thanks to the introduction of protocols for 3D acquisition and analysis of electron diffraction data. This method provides single-crystal data of structure solution and refinement quality, allowing the atomic structure determination of those materials that remained hitherto unknown because of their limited crystallinity. Several experimental protocols exist, which share the common idea of sampling a sequence of diffraction patterns while the crystal is tilted around a noncrystallographic axis, namely, the goniometer axis of the transmission electron microscope sample stage. This Outlook reviews most important 3D electron diffraction applications for different kinds of samples and problematics, related with both materials and life sciences. Structure refinement including dynamical scattering is also briefly discussed.
|
|
| 10. |
- Grushko, B., et al.
(författare)
-
Al-rich region of Al-Pt
- 2013
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 580, s. 618-625
-
Tidskriftsartikel (refereegranskat)abstract
- The constitution of the Al-rich part of the Al-Pt alloy system is revised. Apart from the previously reported equilibrium Al4Pt, Al21Pt8 and Al2Pt phases, a complex intermetallic was revealed at 7576 at.% Al between 801 and 915 degrees C. Its structure determined by electron diffraction is orthorhombic (Bmmb, a = 1.983, b = 1.636 and c = 1.422 nm).
|
|
