| 1. |
- Niemi, MEK, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 2. |
- Dehasque, Marianne, et al.
(författare)
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Inference of natural selection from ancient DNA
- 2020
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Ingår i: Evolution Letters. - : JOHN WILEY & SONS LTD. - 2056-3744. ; 4:2, s. 94-108
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Evolutionary processes, including selection, can be indirectly inferred based on patterns of genomic variation among contemporary populations or species. However, this often requires unrealistic assumptions of ancestral demography and selective regimes. Sequencing ancient DNA from temporally spaced samples can inform about past selection processes, as time series data allow direct quantification of population parameters collected before, during, and after genetic changes driven by selection. In this Comment and Opinion, we advocate for the inclusion of temporal sampling and the generation of paleogenomic datasets in evolutionary biology, and highlight some of the recent advances that have yet to be broadly applied by evolutionary biologists. In doing so, we consider the expected signatures of balancing, purifying, and positive selection in time series data, and detail how this can advance our understanding of the chronology and tempo of genomic change driven by selection. However, we also recognize the limitations of such data, which can suffer from postmortem damage, fragmentation, low coverage, and typically low sample size. We therefore highlight the many assumptions and considerations associated with analyzing paleogenomic data and the assumptions associated with analytical methods.
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| 3. |
- Gunawidjaja, Philips N., et al.
(författare)
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Biomimetic Apatite Mineralization Mechanisms of Mesoporous Bioactive Glasses as Probed by Multinuclear ³¹P, ²⁹Si, ²³Na and ¹³C Solid State NMR
- 2010
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:45, s. 19345-19356
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Tidskriftsartikel (refereegranskat)abstract
- An array of magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy experiments is applied to explore the surface reactions of a mesoporous bioactive glass (MBG) of composition Ca0.10Si0.85P0.04O1.90 when subjected to a simulated body fluid (SBF) for variable intervals. Powder X-ray diffraction and 31P NMR techniques are employed to quantitatively monitor the formation of an initially amorphous calcium phosphate surface layer and its subsequent crystallization into hydroxycarbonate apatite (HCA). Prior to the onset of HCA formation, 1H → 29Si cross-polarization (CP) NMR evidence dissolution of calcium ions; a slightly increased connectivity of the speciation of silicate ions is observed at the MBG surface over 1 week of SBF exposure. The incorporation of carbonate and sodium ions into the bioactive orthophosphate surface layer is explored by 1H → 13C CPMAS and 23Na NMR, respectively. We discuss similarities and distinctions in composition−bioactivity relationships established for traditional melt-prepared bioglasses compared to MBGs. The high bioactivity of phosphorus-bearing MBGs is rationalized to stem from an acceleration of their surface reactions due to presence of amorphous calcium orthophosphate clusters of the MBG pore wall.
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| 4. |
- Gunawidjaja, Philips N., et al.
(författare)
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Local structures of mesoporous bioactive glasses and their surface alterations in vitro : inferences from solid-state nuclear magnetic resonance
- 2012
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Ingår i: Philosophical Transactions. Series A. - : The Royal Society. - 1364-503X .- 1471-2962. ; 370:1963, s. 1376-1399
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Tidskriftsartikel (refereegranskat)abstract
- We review the benefits of using Si-29 and H-1 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy for probing the local structures of both bulk and surface portions of mesoporous bioactive glasses (MBGs) of the CaO-SiO2-(P2O5) system. These mesoporous materials exhibit an ordered pore arrangement, and are promising candidates for improved bone and tooth implants. We discuss experimental MAS NMR results from three MBGs displaying different Ca, Si and P contents: the Si-29 NMR spectra were recorded either directly by employing radio-frequency pulses to Si-29, or by magnetization transfers from neighbouring protons using cross polarization, thereby providing quantitative information about the silicate speciation present in the pore wall and at the MBG surface, respectively. The surface modifications were monitored for the three MBGs during their immersion in a simulated body fluid (SBF) for intervals between 30 min and one week. The results were formulated as a reaction sequence describing the interconversions between the distinct silicate species. We generally observed a depletion of Ca2+ ions at the MBG surface, and a minor condensation of the silicate-surface network over one week of SBF soaking.
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| 5. |
- Gunawidjaja, Philips N., et al.
(författare)
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Quantifying apatite formation and cation leaching from mesoporous bioactive glasses in vitro : a SEM, solid-state NMR and powder XRD study
- 2012
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 22:15, s. 7214-7223
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Tidskriftsartikel (refereegranskat)abstract
- By employing solid-state nuclear magnetic resonance (NMR) spectroscopy, powder X-ray diffraction (PXRD), and scanning electron microscopy coupled with energy-dispersive X-ray (EDX) spectroscopy, we compare the biomimetic growth of calcium hydroxyapatite (HA) from an ordered mesoporous bioactive glass (MBG) in simulated body fluid (SBF) and buffered water solutions. For the latter medium, we also examine the effects of using two different MBG concentrations. We evaluate the predicting powers of PXRD and P-31 NMR for directly quantifying the relative amounts of biomimetic amorphous calcium phosphate (ACP) and HA: we observe a very good agreement between the two analytical techniques. Thanks to their mesoporous channel system, fluids readily penetrate throughout sub-mm sized MBG grains, as evidenced by EDX. The latter revealed distinct element-mappings across the material after its exposure to SBF compared to water. Under our in vitro conditions involving relatively high MBG-loadings in the solutions, the HA formation reduces in SBF relative to buffered water, particularly for increasing MBG concentration. These features stem from a high [Ca2+]/[PO43-] ratio resulting in the fluid medium, which retards the HA crystallization by inducing a rapid ACP precipitation and an accompanying depletion of phosphate ions in the solution. This has bearings on the design of bioactivity comparisons of bioglasses exhibiting significantly different cation compositions.
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| 6. |
- Izquierdo-Barba, Isabel, et al.
(författare)
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High-performance mesoporous bioceramics mimicking bone mineralization
- 2008
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 20:9, s. 3191-3198
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Tidskriftsartikel (refereegranskat)abstract
- The preparation of bioceramics with ordered mesoporous structures is of importance for biomedical technology, for the design of bone and dental grafts with regeneration purposes. Here we demonstrate that hexagonal mesoporous SiO2-CaO-P2O5 bioglasses (MBG) with high calcium content are the first known bioceramics that exhibit amorphous calcium phosphate (ACP)-octacalcium phosphate (OCP)-calcium deficient carbonatehydroxyapatite (CDHA) maturation as biomineralization governing mechanism in simulated body fluid (SBF), similarly to the in vivo biomineralization process. The unique characteristics of hexagonal MBGs lead to a local acid pH at the bioceramic surface that allows the formation of metastable OCP. Besides, 3D cubic MBG has been also synthesized, exhibiting higher surface area and porosity. The 3D reconstruction carried out by electron microscopy evidence a 3D bicontinuous network comprising a pair of rods mutually intertwined, creating the pore system available in three dimensions. This 3D pore system provides not only high surface area and porosity but also easier interchange of ions, increasing mass transport and diffusion processes. The final result is that 3D cubic MBGs exhibit an accelerated bioactivity behavior, forming a bonelike apatite phase on the surface, I h after coming into contact with SBF.
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| 7. |
- Leonova, Ekaterina, et al.
(författare)
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Multinuclear Solid-State NMR Studies of Ordered Mesoporous Bioactive Glasses
- 2008
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 112:14, s. 5552-5562
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Tidskriftsartikel (refereegranskat)abstract
- The local structures of highly ordered mesoporous bioactive CaO-SiO2-P2O5 glasses were investigated for variable Ca contents. 1H NMR revealed a diversity of hydrogen-bonded and "isolated" surface silanols as well as adsorbed water molecules. The structural roles of Si and P were explored using a combination of 29Si and 31P magic-angle spinning (MAS) nuclear magnetic resonance (NMR) techniques; the proximities of Si and P to protons were studied through cross-polarization-based experiments, including 1H-29Si and 1H-31P hetero-nuclear two-dimensional correlation spectroscopy. The results are consistent with SiO2 being the main pore-wall component, whereas P is present as a separate amorphous calcium orthophosphate phase, which is dispersed over the pore wall as nanometer-sized clusters. The excess Ca that is not consumed in the phosphate phase modifies the silica glass network where it associates at/near the mesoporous surface. This biphasic structural model of the pore wall leads to the high accessibility of both Ca and P to body fluids, and its relation to the experimentally demonstrated high in vitro bioactivities of these materials is discussed.
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| 8. |
- Mathew, Renny, et al.
(författare)
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Direct Probing of the Phosphate-Ion Distribution in Bioactive Silicate Glasses by Solid-State NMR : Evidence for Transitions between Random/Clustered Scenarios
- 2013
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 25:9, s. 1877-1885
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Tidskriftsartikel (refereegranskat)abstract
- By employing P-31 multiple-quantum coherence-based solid-state nuclear magnetic resonance spectroscopy, we present the first comprehensive experimental assessment of the nature of the orthophosphate ion distributions in silicate based bioactive glasses (BGs). Results are provided both from melt prepared BG and evaporation-induced self-assembly-derived mesoporous bioactive glass (MEBG) structures of distinct compositions. The phosphate species are randomly dispersed in melt-derived BGs (comprising 44-55 mol % SiO2) of the Na2O-CaO-SiO2-P2O5 system, whereas a Si-rich (86 mol % SiO2) and Ca-poor ordered MBG structure exhibits nanometer-sized amorphous calcium phosphate clusters, conservatively estimated to comprise at least nine orthophosphate groups. A Ca-richer MBG (58 mol % SiO2) reveals a less pronounced phosphate clustering. We rationalize the variable structural role of P in these amorphous biomatetials.
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| 9. |
- Mathew, Renny, et al.
(författare)
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Proton Environments in Biomimetic Calcium Phosphates Formed from Mesoporous Bioactive CaO-SiO2-P2O5 Glasses in Vitro : Insights from Solid-State NMR
- 2017
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:24, s. 13223-13238
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Tidskriftsartikel (refereegranskat)abstract
- When exposed to body fluids, mesoporous bioactive glasses (MBGs) of the CaO-SiO2-P2O5 system develop a bone-bonding surface layer that initially consists of amorphous calcium phosphate (ACP), which transforms into hydroxy-carbonate apatite (HCA) with a very similar composition as bone/dentin mineral. Information from various H-1-based solid-state nuclear magnetic resonance (NMR) experiments was combined to elucidate the evolution of the proton speciations both at the MBG surface and within each ACP/HCA constituent of the biomimetic :phosphate layer a formed when each of three MBGs with distinct Ca, Si; and P contents was immersed in a simulated body fluid (SBF) for variable periods between 15 min and 30 days. Directly excited magic-angle-spinning (MAS) H-1 NMR spectra mainly reflect the MBG component, whose surface is rich in water and silanol (SiOH) moieties. Double-quantum-single-quantum correlation H-1 NMR experimentation At fast MAS revealed their interatomic proximities. The comparatively minor H species of each ACP and HCA component were probed selectively by heteronuclear H-1-P-31 NMR experimentation. The initially prevailing ACP phase comprises H2O and nonapatitic.HPO42-/PO43- groups, whereas for prolonged MBG soaking Over days, a well-progressed ACP -> HCA transformation was evidenced by a dominating (OH)-H-1 resonance from HCA. We show that H-1-detected H-1 -> P-31 cross polarization NMR is markedly more sensitive than utilizing powder X-ray diffraction or P-31 NMR for detecting the onset of HCA formation, notably so for P-bearing (M)BGs. In relation to the long-standing controversy as to whether bone mineral comprises ACP and/or forms via an ACP precursor, we discuss a recently accepted structural core-shell picture of both synthetic and biological HCA, highlighting the close relationship between the disordered surface layer and ACP.
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| 10. |
- Mathew, Renny, et al.
(författare)
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Solid-State (31)P and (1)H NMR Investigations of Amorphous and Crystalline Calcium Phosphates Grown Biomimetically From a Mesoporous Bioactive Glass
- 2011
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:42, s. 20572-20582
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Tidskriftsartikel (refereegranskat)abstract
- By exploiting (1)H and (31)P magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy, we explore the proton and orthophosphate environments in biomimetic amorphous calcium phosphate (ACP) and hydroxyapatite (HA), as grown in vitro at the surface of a 10CaO-85SiO(2)-5P(2)O(5) mesoporous bioactive glass (MBG) in either a simulated body fluid or buffered water. Transmission electron microscopy confirmed the presence of a calcium phosphate layer comprising nanocrystalline HA Two-dimensional (1)H-(31)P heteronudear correlation NMR established predominantly (1)H(2)O <->(31)PO(4)(3-) and O(1)H <->(31)PO(4)(3-) contacts in the amorphous and crystalline component, respectively, of the MBG surface-layer; these two pairs exhibit distinctly different (1)H <->(31)P cross-polarization dynamics, revealing a twice as large squared effective (1)H-(31)P dipolar coupling constant in ACP compared with HA. These respective observations are mirrored in synthetic (well-crystalline) HA, and the amorphous calcium orthophosphate (CaP) clusters that are present in the pristine MBG pore walls: besides highlighting very similar local (1)H and (31)P environments in synthetic and biomimetic HA, our findings evidence closely related NMR characteristics, and thereby similar local structures, of the CaP clusters in the pristine MBG relative to biomimetic ACP.
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