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- Andersson, Hanna, 1979, et al.
(författare)
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Solvent Effects on Nitrogen Chemical Shifts
- 2015
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Ingår i: Annual Reports on NMR Spectroscopy. - : Elsevier. - 0066-4103. - 9780128021231 ; 86, s. 73-210
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Forskningsöversikt (refereegranskat)abstract
- Due to significant developments in cryogenic probe technology and the easy access to inverse detection pulse programmes (HSQC, HMBC), the sensitivity of nitrogen NMR has lately vastly improved. As a consequence, nitrogen NMR has turned into a useful and commonly available tool for solution studies of molecular structure and properties for small organic compounds likewise biopolymers. The high sensitivity of the nitrogen lone pair to changes in the molecular environment, alterations in intra- and intermolecular interactions, and in molecular conformation along with its wide, up to 1200 ppm chemical shift dispersion make nitrogen NMR to an exceptionally sensitive reporter tool. The nitrogen chemical shift has been applied in various fields of chemistry, including for instance the studies of transition metal complexes, chemical reactions such as N-alkylation and N-oxidation, tautomerization, protonation–deprotonation equilibria, hydrogen and halogen bonding, and elucidation of molecular conformation and configuration. The 15N NMR data observed in the investigation of these molecular properties and processes is influenced by the medium it is acquired in. This influence may be due to direct coordination of solvent molecules to transition metal complexes, alteration of tautomerization equilibria, and solvent polarity induced electron density changes of conjugated systems, for example. Thus, the solvent may significantly alter the observed nitrogen NMR shifts. This review aims to provide an overview of solvent effects of practical importance, and discusses selected experimental reports from various subfields of chemistry.
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- Aspengren, Sara, 1977, et al.
(författare)
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Rapport forskarenkät 2015
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Resultatet av den användarenkät som gjordes av Universitetsbiblioteket bland Göteborgs universitets disputerade forskare och doktorander 2014.
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| 7. |
- Beausang, Angela, et al.
(författare)
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"Möjligheten att rädda några av dessa kvinnors liv har inte vägts in"
- 2014
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Ingår i: Dagens Medicin. - : Dagens Medicin.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Namnet på Socialstyrelsens vägledning lyder: Hur upptäcka våldsutsatthet? Ja, det kan man verkligen fråga sig efter att ha läst detta föga vägledande dokument, skriver ett stort antal kritiska debattörer.
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| 8. |
- Bedin, Michele, et al.
(författare)
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Counterion influence on the N-I-N halogen bond
- 2015
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Ingår i: Chemical Science. - 2041-6539 .- 2041-6520. ; 6:7, s. 3746-3756
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Tidskriftsartikel (refereegranskat)abstract
- A detailed investigation of the influence of counterions on the [N–I–N]+ halogen bond in solution, in the solid state and in silico is presented. Translational diffusion coefficients indicate close attachment of counterions to the cationic, three-center halogen bond in dichloromethane solution. Isotopic perturbation of equilibrium NMR studies performed on isotopologue mixtures of regioselectively deuterated and nondeuterated analogues of the model system showed that the counterion is incapable of altering the symmetry of the [N–I–N]+ halogen bond. This symmetry remains even in the presence of an unfavorable geometric restraint. A high preference for the symmetric geometry was found also in the solid state by single crystal X-ray crystallography. Molecular systems encompassing weakly coordinating counterions behave similarly to the corresponding silver(I) centered coordination complexes. In contrast, systems possessing moderately or strongly coordinating anions show a distinctly different behavior. Such silver(I) complexes are converted into multi-coordinate geometries with strong Ag–O bonds, whereas the iodine centered systems remain linear and lack direct charge transfer interaction with the counterion, as verified by 15N NMR and DFT computation. This suggests that the [N–I–N]+ halogen bond may not be satisfactorily described in terms of a pure coordination bond typical of transition metal complexes, but as a secondary bond with a substantial charge-transfer character.
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| 9. |
- Bedin, Michele, et al.
(författare)
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Counterion influence on the N-I-N halogen bond.
- 2015
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Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 6:7, s. 3746-3756
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Tidskriftsartikel (refereegranskat)abstract
- A detailed investigation of the influence of counterions on the [N-I-N]+ halogen bond in solution, in the solid state and in silico is presented. Translational diffusion coefficients indicate close attachment of counterions to the cationic, three-center halogen bond in dichloromethane solution. Isotopic perturbation of equilibrium NMR studies performed on isotopologue mixtures of regioselectively deuterated and nondeuterated analogues of the model system showed that the counterion is incapable of altering the symmetry of the [N-I-N]+ halogen bond. This symmetry remains even in the presence of an unfavorable geometric restraint. A high preference for the symmetric geometry was found also in the solid state by single crystal X-ray crystallography. Molecular systems encompassing weakly coordinating counterions behave similarly to the corresponding silver(i) centered coordination complexes. In contrast, systems possessing moderately or strongly coordinating anions show a distinctly different behavior. Such silver(i) complexes are converted into multi-coordinate geometries with strong Ag-O bonds, whereas the iodine centered systems remain linear and lack direct charge transfer interaction with the counterion, as verified by 15N NMR and DFT computation. This suggests that the [N-I-N]+ halogen bond may not be satisfactorily described in terms of a pure coordination bond typical of transition metal complexes, but as a secondary bond with a substantial charge-transfer character.
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| 10. |
- Berghard, Anna, et al.
(författare)
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Lhx2-dependent specification of olfactory sensory neurons is required for successful integration of olfactory, vomeronasal, and GnRH neurons
- 2012
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Ingår i: The FASEB Journal. - : Federation of American Society of Experimental Biology (FASEB). - 0892-6638 .- 1530-6860. ; 26:8, s. 3464-3472
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Tidskriftsartikel (refereegranskat)abstract
- Inactivation of the LIM-homeodomain 2 gene (Lhx2) results in a severe defect in specification of olfactory sensory neurons (OSNs). However, the ramifications of lack of Lhx2-dependent OSN specification for formation of the primary olfactory pathway have not been addressed, since mutant mice die in utero. We have analyzed prenatal and postnatal consequences of conditionally inactivating Lhx2 selectively in OSNs. A cell-autonomous effect is that OSN axons cannot innervate their target, the olfactory bulb. Moreover, the lack of Lhx2 in OSNs causes unpredicted, non-cell-autonomous phenotypes. First, the olfactory bulb shows pronounced hypoplasia in adults, and the data suggest that innervation by correctly specified OSNs is necessary for adult bulb size and organization. Second, absence of an olfactory nerve in the conditional mutant reveals that the vomeronasal nerve is dependent on olfactory nerve formation. Third, the lack of a proper vomeronasal nerve prevents migration of gonadotropin-releasing hormone (GnRH) cells the whole distance to their final positions in the hypothalamus during embryo development. As adults, the conditional mutants do not pass puberty, and these findings support the view of an exclusive nasal origin of GnRH neurons in the mouse. Thus, Lhx2 in OSNs is required for functional development of three separate systems.—Berghard, A., Hägglund, A.-C., Bohm, S., and Carlsson, L. Lhx2-dependent specification of olfactory sensory neurons is required for successful integration of olfactory, vomeronasal, and GnRH neurons.
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