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Gustafsson DR, Olsson U. Flyway homogenisation or differentiation? Insights from the phylogeny of the sandpiper (Charadriiformes: Scolopacidae: Calidrinae) wing louse genus Lunaceps (Phthiraptera: Ischnocera). Int J Parasitol 2012; 42:93-102. [DOI: 10.1016/j.ijpara.2011.11.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Revised: 11/01/2011] [Accepted: 11/02/2011] [Indexed: 11/16/2022]
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Alström P, Höhna S, Gelang M, Ericson PGP, Olsson U. Non-monophyly and intricate morphological evolution within the avian family Cettiidae revealed by multilocus analysis of a taxonomically densely sampled dataset. BMC Evol Biol 2011; 11:352. [PMID: 22142197 PMCID: PMC3261208 DOI: 10.1186/1471-2148-11-352] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Accepted: 12/05/2011] [Indexed: 11/10/2022] Open
Abstract
Background The avian family Cettiidae, including the genera Cettia, Urosphena, Tesia, Abroscopus and Tickellia and Orthotomus cucullatus, has recently been proposed based on analysis of a small number of loci and species. The close relationship of most of these taxa was unexpected, and called for a comprehensive study based on multiple loci and dense taxon sampling. In the present study, we infer the relationships of all except one of the species in this family using one mitochondrial and three nuclear loci. We use traditional gene tree methods (Bayesian inference, maximum likelihood bootstrapping, parsimony bootstrapping), as well as a recently developed Bayesian species tree approach (*BEAST) that accounts for lineage sorting processes that might produce discordance between gene trees. We also analyse mitochondrial DNA for a larger sample, comprising multiple individuals and a large number of subspecies of polytypic species. Results There are many topological incongruences among the single-locus trees, although none of these is strongly supported. The multi-locus tree inferred using concatenated sequences and the species tree agree well with each other, and are overall well resolved and well supported by the data. The main discrepancy between these trees concerns the most basal split. Both methods infer the genus Cettia to be highly non-monophyletic, as it is scattered across the entire family tree. Deep intraspecific divergences are revealed, and one or two species and one subspecies are inferred to be non-monophyletic (differences between methods). Conclusions The molecular phylogeny presented here is strongly inconsistent with the traditional, morphology-based classification. The remarkably high degree of non-monophyly in the genus Cettia is likely to be one of the most extraordinary examples of misconceived relationships in an avian genus. The phylogeny suggests instances of parallel evolution, as well as highly unequal rates of morphological divergence in different lineages. This complex morphological evolution apparently misled earlier taxonomists. These results underscore the well-known but still often neglected problem of basing classifications on overall morphological similarity. Based on the molecular data, a revised taxonomy is proposed. Although the traditional and species tree methods inferred much the same tree in the present study, the assumption by species tree methods that all species are monophyletic is a limitation in these methods, as some currently recognized species might have more complex histories.
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Öhlund M, Höglund O, Olsson U, Lagerstedt AS. Laparoscopic ovariectomy in dogs: a comparison of the LigaSure™ and the SonoSurg™ systems. J Small Anim Pract 2011; 52:290-4. [DOI: 10.1111/j.1748-5827.2011.01060.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Persson Osowski C, Fjellström C, Olsson U, Göranzon H. Agreement between child and parent reports of 10- to 12-year-old children’s meal pattern and intake of snack foods. J Hum Nutr Diet 2011; 25:50-8. [DOI: 10.1111/j.1365-277x.2011.01169.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Alström P, Fregin S, Norman JA, Ericson PG, Christidis L, Olsson U. Multilocus analysis of a taxonomically densely sampled dataset reveal extensive non-monophyly in the avian family Locustellidae. Mol Phylogenet Evol 2011; 58:513-26. [DOI: 10.1016/j.ympev.2010.12.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Revised: 12/17/2010] [Accepted: 12/20/2010] [Indexed: 11/29/2022]
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Sangster G, Alström P, Forsmark E, Olsson U. Multi-locus phylogenetic analysis of Old World chats and flycatchers reveals extensive paraphyly at family, subfamily and genus level (Aves: Muscicapidae). Mol Phylogenet Evol 2010; 57:380-92. [DOI: 10.1016/j.ympev.2010.07.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2010] [Revised: 06/25/2010] [Accepted: 07/08/2010] [Indexed: 10/19/2022]
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Castelletto V, McKendrick JE, Hamley IW, Olsson U, Cenker C. PEGylated amyloid peptide nanocontainer delivery and release system. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:11624-11627. [PMID: 20666427 DOI: 10.1021/la101806z] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
A micellar nanocontainer delivery and release system is designed on the basis of a peptide-polymer conjugate. The hybrid molecules self-assemble into micelles comprising a modified amyloid peptide core surrounded by a PEG corona. The modified amyloid peptide previously studied in our group forms helical ribbons based on a beta-sheet motif and contains beta-amino acids that are excluded from the beta-sheet structure, thus being potentially useful as fibrillization inhibitors. In the model peptide-PEG hybrid system studied, enzymatic degradation using alpha-chymotrypsin leads to selective cleavage close to the PEG-peptide linkage, break up of the micelles, and release of peptides in unassociated form. The release of monomeric peptide is useful because aggregation of the released peptide into beta-sheet amyloid fibrils is not observed. This concept has considerable potential in the targeted delivery of peptides for therapeutic applications.
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Medronho B, Rodrigues M, Miguel MG, Olsson U, Schmidt C. Shear-induced defect formation in a nonionic lamellar phase. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:11304-11313. [PMID: 20373778 DOI: 10.1021/la100627z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
(2)H NMR experiments on a nonionic oriented lamellar phase demonstrate that shear flow induces structural defects in the lamellar structure. These substantial structural changes give rise to a transition from a viscous to a solidlike behavior; the elastic modulus of presheared samples was found to increase, reversibly, with the applied preshear rate. A similar behavior was found when step-cycling the temperature toward the layer-to-multilamellar-vesicle transition and back at constant shear rate. However, while shear rate controls the defect density, the temperature is found to control the defect rigidity. The lamellar phase exhibits a shear-thinning behavior under steady shear conditions, following the power law eta approximately gamma(n), with n approximately -0.4. Both the shear thinning and the elastic behavior are in agreement with the available theoretical models. The observed shear-induced structural defects are reversible and can be regarded as a pretransition prior to the shear-induced formation of multilamellar vesicles.
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Castelletto V, Hamley I, Cenker C, Olsson U. Influence of Salt on the Self-Assembly of Two Model Amyloid Heptapeptides. J Phys Chem B 2010; 114:8002-8. [DOI: 10.1021/jp102744g] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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60
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Olsson U, Alström P, Svensson L, Aliabadian M, Sundberg P. The Lanius excubitor (Aves, Passeriformes) conundrum—Taxonomic dilemma when molecular and non-molecular data tell different stories. Mol Phylogenet Evol 2010; 55:347-57. [DOI: 10.1016/j.ympev.2009.11.010] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Revised: 11/03/2009] [Accepted: 11/11/2009] [Indexed: 11/28/2022]
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Saitoh T, Alström P, Nishiumi I, Shigeta Y, Williams D, Olsson U, Ueda K. Old divergences in a boreal bird supports long-term survival through the Ice Ages. BMC Evol Biol 2010; 10:35. [PMID: 20128930 PMCID: PMC2848155 DOI: 10.1186/1471-2148-10-35] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Accepted: 02/04/2010] [Indexed: 11/12/2022] Open
Abstract
Background Unlike northern Europe and most of northern North America, the Eastern Palearctic and the northwesternmost tip of North America are believed to have been almost unglaciated during the Quarternary glacial periods. This could have facilitated long-term survival of many organisms in that area. To evaluate this, we studied the phylogeography in east Asia and Alaska of a boreal migratory passerine bird, the Arctic Warbler Phylloscopus borealis, and compared our results with published data on especially North American species. Results In a sample of 113 individuals from 18 populations we identified 42 haplotypes of the mitochondrial cytochrome b gene, which separated into three clades: A - Alaska and mainland Eurasia (except Kamchatka); B - Kamchatka, Sakhalin and Hokkaido; and C - Honshu, Shikoku and Kyushu (i.e. Japan except Hokkaido). The oldest split among these clades, between A/B and C, is estimated to have taken place sometime between the mid Pliocene and early Pleistocene, and the second divergence, between clades A and B, in the early to mid Pleistocene. Within all of the three main clades, there are signs of population expansion. Conclusions The Arctic Warbler separated into three main clades in close succession around the Pliocene/Pleistocene border, with the two northern clades diverging last. All three clades probably experienced population bottlenecks during the Pleistocene as a result of range shifts and contractions, but nevertheless survived and maintained their integrities. Several other clades of Northeastern Palearctic birds are noted to have diversified during the Pliocene. In contrast, avian species or phylogroups presently occupying formerly glaciated North American ground are generally younger. The differences between these regions could be due to slower speciation rates in the Eastern Palearctic due to less fragmentation of forest habitats during glacial periods, or to longer survival of Eastern Palearctic clades as a result of less severe conditions in that region compared to northern North America. Several other Palearctic organisms show concordant biogeographical patterns to that of the Arctic Warbler, indicating common causes of their diversifications.
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Medronho B, Schmidt C, Olsson U, Miguel MG. Size determination of shear-induced multilamellar vesicles by rheo-NMR spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:1477-1481. [PMID: 20099913 DOI: 10.1021/la903682p] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A model for analyzing the deuterium ((2)H) NMR line shapes of D(2)O in surfactant multilamellar vesicle (MLV, "onion") systems is proposed. The assumption of the slow exchange of water molecules between adjacent layers implies that the (2)H NMR line shape is simply given by a sum of Lorentzians if the condition of motional narrowing is also fulfilled. Using the classical two-step model for the NMR relaxation in structured fluids allows us to calculate how the NMR line shape depends on the MLV size. The model is tested on two different MLV systems for which the NMR line shapes are measured as a function of the applied shear rate using rheo-NMR. The MLV sizes obtained are in good agreement with previous data from rheo-small-angle light scattering.
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Angelico R, Rossi CO, Ambrosone L, Palazzo G, Mortensen K, Olsson U. Ordering fluctuations in a shear-banding wormlike micellar system. Phys Chem Chem Phys 2010; 12:8856-62. [DOI: 10.1039/b926152d] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Kjeldsen SE, Stålhammar J, Hasvold P, Bodegard J, Olsson U, Russell D. Effects of losartan vs candesartan in reducing cardiovascular events in the primary treatment of hypertension. J Hum Hypertens 2009; 24:263-73. [PMID: 19890371 PMCID: PMC2834374 DOI: 10.1038/jhh.2009.77] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Although angiotensin receptor blockers have different receptor binding properties no comparative studies with cardiovascular disease (CVD) end points have been performed within this class of drugs. The aim of this study was to test the hypothesis that there are blood pressure independent CVD-risk differences between losartan and candesartan treatment in patients with hypertension without known CVD. Seventy-two primary care centres in Sweden were screened for patients who had been prescribed losartan or candesartan between the years 1999 and 2007. Among the 24 943 eligible patients, 14 100 patients were diagnosed with hypertension and prescribed losartan (n=6771) or candesartan (n=7329). Patients were linked to Swedish national hospitalizations and death cause register. There was no difference in blood pressure reduction when comparing the losartan and candesartan groups during follow-up. Compared with the losartan group, the candesartan group had a lower adjusted hazard ratio for total CVD (0.86, 95% confidence interval (CI) 0.77–0.96, P=0.0062), heart failure (0.64, 95% CI 0.50–0.82, P=0.0004), cardiac arrhythmias (0.80, 95% CI 0.65–0.92, P=0.0330), and peripheral artery disease (0.61, 95% CI 0.41–0.91, P=0.0140). No difference in blood pressure reduction was observed suggesting that other mechanisms related to different pharmacological properties of the drugs may explain the divergent clinical outcomes.
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Castelletto V, Hamley IW, Harris PJF, Olsson U, Spencer N. Influence of the solvent on the self-assembly of a modified amyloid beta peptide fragment. I. Morphological investigation. J Phys Chem B 2009; 113:9978-87. [PMID: 19555054 DOI: 10.1021/jp902860a] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The solvent-induced transition between self-assembled structures formed by the peptide AAKLVFF is studied via electron microscopy, light scattering, and spectroscopic techniques. The peptide is based on a core fragment of the amyloid beta-peptide, KLVFF, extended by two alanine residues. AAKLVFF exhibits distinct structures of twisted fibrils in water or nanotubes in methanol. For intermediate water/methanol compositions, these structures are disrupted and replaced by wide filamentous tapes that appear to be lateral aggregates of thin protofilaments. The orientation of the beta-strands in the twisted tapes or nanotubes can be deduced from X-ray diffraction on aligned stalks, as well as FT-IR experiments in transmission compared to attenuated total reflection. Strands are aligned perpendicular to the axis of the twisted fibrils or the nanotubes. The results are interpreted in light of recent results on the effect of competitive hydrogen bonding upon self-assembly in soft materials in water/methanol mixtures.
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Knaapila M, Svensson C, Barauskas J, Zackrisson M, Nielsen SS, Toft KN, Vestergaard B, Arleth L, Olsson U, Pedersen JS, Cerenius Y. A new small-angle X-ray scattering set-up on the crystallography beamline I711 at MAX-lab. JOURNAL OF SYNCHROTRON RADIATION 2009; 16:498-504. [PMID: 19535864 DOI: 10.1107/s0909049509018986] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Accepted: 05/19/2009] [Indexed: 05/27/2023]
Abstract
A small-angle X-ray scattering (SAXS) set-up has recently been developed at beamline I711 at the MAX II storage ring in Lund (Sweden). An overview of the required modifications is presented here together with a number of application examples. The accessible q range in a SAXS experiment is 0.009-0.3 A(-1) for the standard set-up but depends on the sample-to-detector distance, detector offset, beamstop size and wavelength. The SAXS camera has been designed to have a low background and has three collinear slit sets for collimating the incident beam. The standard beam size is about 0.37 mm x 0.37 mm (full width at half-maximum) at the sample position, with a flux of 4 x 10(10) photons s(-1) and lambda = 1.1 A. The vacuum is of the order of 0.05 mbar in the unbroken beam path from the first slits until the exit window in front of the detector. A large sample chamber with a number of lead-throughs allows different sample environments to be mounted. This station is used for measurements on weakly scattering proteins in solutions and also for colloids, polymers and other nanoscale structures. A special application supported by the beamline is the effort to establish a micro-fluidic sample environment for structural analysis of samples that are only available in limited quantities. Overall, this work demonstrates how a cost-effective SAXS station can be constructed on a multipurpose beamline.
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Gelang M, Cibois A, Pasquet E, Olsson U, Alström P, Ericson PGP. Phylogeny of babblers (Aves, Passeriformes): major lineages, family limits and classification. ZOOL SCR 2009. [DOI: 10.1111/j.1463-6409.2008.00374.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Fregin S, Haase M, Olsson U, Alström P. Multi-locus phylogeny of the family Acrocephalidae (Aves: Passeriformes)--the traditional taxonomy overthrown. Mol Phylogenet Evol 2009; 52:866-78. [PMID: 19393746 DOI: 10.1016/j.ympev.2009.04.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Revised: 04/08/2009] [Accepted: 04/15/2009] [Indexed: 10/20/2022]
Abstract
We present the first study of the warbler family Acrocephalidae based on one mitochondrial and three nuclear DNA loci, in total approximately 2900 bp, including most or all of the species in three (Acrocephalus, Hippolais and Chloropeta) of the four genera and one species in the fourth genus (Nesillas) in this family. All three genera were suggested to be non-monophyletic, although the non-monophyly of Acrocephalus is not fully convincingly demonstrated. Six major clades were found, which agreed largely with the results from two earlier mitochondrial studies, and for which the names Hippolais, Iduna, Acrocephalus, Calamocichla, Notiocichla and Calamodus have been used. However, the results also revealed some new constellations, due to better resolution of deeper nodes and the inclusion of more taxa. The taxonomic implications are discussed.
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Bucak S, Cenker C, Nasir I, Olsson U, Zackrisson M. Peptide nanotube nematic phase. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:4262-5. [PMID: 19275132 DOI: 10.1021/la804175h] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The self-assembly of the trifluoroacetate salt of the short peptide (ala)6-lys (A6K) in water has been investigated by cryo-transmission electron microscopy and small-angle X-ray scattering. For concentrations below ca. 12%, the peptide does not self-assemble but forms a molecularly dispersed solution. Above this critical concentration, however, A6K self-assembles into several-micrometer-long hollow nanotubes with a monodisperse cross-sectional radius of 26 nm. Because the peptides carry a positive charge, the nanotubes are charge-stabilized. Because of the very large aspect ratio, the tubes form an ordered phase that presumably is nematic.
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Bulut S, Hamit J, Olsson U, Kato T. On the concentration-induced growth of nonionic wormlike micelles. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2008; 27:261-273. [PMID: 18972143 DOI: 10.1140/epje/i2008-10379-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Accepted: 09/23/2008] [Indexed: 05/27/2023]
Abstract
We present a comprehensive study of the concentration-induced growth of nonionic wormlike micelles in dilute solutions, below the overlap concentration, where we combine static and dynamic light scattering and NMR self-diffusion. The data are analyzed in detail in terms of the number-averaged contour length, assuming an exponential size distribution, as predicted by theory, and that the micellar flexibility can be described by the wormlike chain model with a certain persistence length. A very good agreement between the different experimental methods is obtained. The number-averaged contour length increases with increasing micelle volume fraction. The data are consistent with a power law, where the power law exponent is in the range 0.5-0.8, depending on the system. The result is in reasonable agreement with the theory of living polymers.
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Nylander JAA, Olsson U, Alström P, Sanmartín I. Accounting for phylogenetic uncertainty in biogeography: a Bayesian approach to dispersal-vicariance analysis of the thrushes (Aves: Turdus). Syst Biol 2008; 57:257-68. [PMID: 18425716 DOI: 10.1080/10635150802044003] [Citation(s) in RCA: 178] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
The phylogeny of the thrushes (Aves: Turdus) has been difficult to reconstruct due to short internal branches and lack of node support for certain parts of the tree. Reconstructing the biogeographic history of this group is further complicated by the fact that current implementations of biogeographic methods, such as dispersal-vicariance analysis (DIVA; Ronquist, 1997), require a fully resolved tree. Here, we apply a Bayesian approach to dispersal-vicariance analysis that accounts for phylogenetic uncertainty and allows a more accurate analysis of the biogeographic history of lineages. Specifically, ancestral area reconstructions can be presented as marginal distributions, thus displaying the underlying topological uncertainty. Moreover, if there are multiple optimal solutions for a single node on a certain tree, integrating over the posterior distribution of trees often reveals a preference for a narrower set of solutions. We find that despite the uncertainty in tree topology, ancestral area reconstructions indicate that the Turdus clade originated in the eastern Palearctic during the Late Miocene. This was followed by an early dispersal to Africa from where a worldwide radiation took place. The uncertainty in tree topology and short branch lengths seems to indicate that this radiation took place within a limited time span during the Late Pliocene. The results support the role of Africa as a probable source area for intercontinental dispersals as suggested for other passerine groups, including basal diversification within the songbird tree.
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Alström P, Olsson U, Lei F, Wang HT, Gao W, Sundberg P. Phylogeny and classification of the Old World Emberizini (Aves, Passeriformes). Mol Phylogenet Evol 2008; 47:960-73. [DOI: 10.1016/j.ympev.2007.12.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2007] [Revised: 12/01/2007] [Accepted: 12/11/2007] [Indexed: 11/17/2022]
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Medronho B, Shafaei S, Szopko R, Miguel MG, Olsson U, Schmidt C. Shear-induced transitions between a planar lamellar phase and multilamellar vesicles: continuous versus discontinuous transformation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:6480-6. [PMID: 18517228 DOI: 10.1021/la800326a] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The shear-induced transitions between an oriented lamellar phase and shear-induced multilamellar vesicles (MLVs) in a nonionic surfactant system were studied by deuterium rheo-NMR spectroscopy as a function of time in start-up experiments at several temperatures and shear rates. By starting from an initial state of oriented lamellae and observing the transformation to the final steady state of MLVs and vice-versa, two different mechanisms were found, depending on the direction of the transition and the initial state. The transition is continuous when MLVs are formed, starting from the oriented lamellar phase. On the other hand, a discontinuous nucleation-and-growth process with a coexistence region is observed when transforming MLVs into an oriented lamellar phase.
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Olsson U, Sundberg P, Alström P, Gelang M, Ericson PGP. What is proper vouchering in phylogenetic studies of birds?--a reply to Peterson et al. (2007). Mol Phylogenet Evol 2008; 48:383-5. [PMID: 18490178 DOI: 10.1016/j.ympev.2008.03.031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Revised: 03/18/2008] [Accepted: 03/26/2008] [Indexed: 10/22/2022]
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Gotter M, Sottmann T, Baciu M, Olsson U, Wennerström H, Strey R. A comprehensive, time-resolved SANS investigation of temperature-change-induced sponge-to-lamellar and lamellar-to-sponge phase transformations in comparison with 2H -NMR results. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2007; 24:277-295. [PMID: 18084713 DOI: 10.1140/epje/i2007-10238-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2007] [Accepted: 11/05/2007] [Indexed: 05/25/2023]
Abstract
Time-resolved small-angle neutron scattering (TR-SANS) was employed to observe temperature-induced phase transitions from the sponge (L (3) to the lamellar ( L (alpha) phase, and vice versa, in the water-oil (n -decane)-non-ionic surfactant ( C(12)E(5) system using both bulk and film contrast. Samples of different bilayer volume fractions phi and solvent viscosities eta were investigated applying various amplitudes of temperature jump DeltaT . The findings of a previous (2)H -NMR study could be confirmed, where the lamellar phase formation was determined to occur through a nucleation and growth process, while it was concluded that the L (3) -phase develops in a mechanistically different and more rapid manner involving uncorrelated passage formation. Likewise, the kinetic trends of the nucleation and growth transition (decreased transition time with increase of phi and DeltaT were witnessed once again. Additionally, NMR and SANS data that demonstrate a strong dependency of that process on solvent viscosity eta are presented. Contrariwise, it is made evident via both SANS and NMR results that the L (alpha) -to-L (3) transition time is independent (within experimental sensitivity) of the varied parameters (phi , DeltaT , eta . Unusual scattering evolution in one experiment, originating from a highly ordered lamellar phase, intriguingly hints that a major rate determining factor is the disruption of long-range order. Furthermore, the bulk contrast investigations give insight into structure peak shifts/development during the transitions, while the film contrast experiments prove the bilayer thickness to be constant throughout the phase transitions and show that there is no evidence for a change in the short-range order of the bilayer structure. The latter was considered possible, due to the different topology of the L (3) and L (alpha) phases. Lastly, an unexpected yet consistent appearance of anisotropic scattering is detected in the L (3) -to- L (alpha) transitions.
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