A curious case of dynamic disorder in pyrrolidine rings elucidated by NMR crystallography

A pharmaceutical exhibits differing dynamics in crystallographically distinct pyrrolidine rings despite being nearly related by symmetry, with one performing ring inversions while the other is constrained to torsional librations. Using 13C solid-state magic-angle spinning (MAS) NMR and DFT calculations, we show that this contrast originates from C-H···H-C close contacts and less efficient C-H···π intermolecular interactions observed in the transition state of the constrained pyrrolidine ring, highlighting the influence of the crystallographic environment on the molecular motion

Investigating discrepancies between experimental solid-state NMR and GIPAW calculation : NC–N 13C and OH⋯O 1H chemical shifts in pyridinium fumarates and their cocrystals

An NMR crystallography analysis is presented for four solid-state structures of pyridine fumarates and their cocrystals, using crystal structures deposited in the Cambridge Crystallographic Data Centre, CCDC. Experimental one-dimensional, one-pulse 1H and 13C cross-polarisation (CP) magic-angle spinning (MAS) nuclear magnetic resonance (NMR) and two-dimensional 14N–1H heteronuclear multiple-quantum coherence MAS NMR spectra are compared with gauge-including projector augmented wave (GIPAW) calculations of the 1H and 13C chemical shifts and the 14N shifts that additionally depend on the quadrupolar interaction. Considering the high ppm (>10 ppm) 1H resonances, while there is good agreement (within 0.4 ppm) between experiment and GIPAW calculation for the hydrogen-bonded NH moieties, the hydrogen-bonded fumaric acid OH resonances are 1.2–1.9 ppm higher in GIPAW calculation as compared to experiment. For the cocrystals of a salt and a salt formed by 2-amino-5-methylpyridinium and 2-amino-6-methylpyridinium ions, a large discrepancy of 4.2 and 5.9 ppm between experiment and GIPAW calculation is observed for the quaternary ring carbon 13C resonance that is directly bonded to two nitrogens (in the ring and in the amino group). By comparison, there is excellent agreement (within 0.2 ppm) for the quaternary ring carbon 13C resonance directly bonded to the ring nitrogen for the salt and cocrystal of a salt formed by 2,6-lutidinium and 2,5-lutidine, respectively

Improving Confidence in Crystal Structure Solutions Using NMR Crystallography: The Case of β-Piroxicam

NMR crystallographic techniques are used to validate a structure of β-piroxicam determined from powder X-ray diffraction (PXRD) with a relatively poor R-factor. Geometry optimization of PXRD- and single-crystal XRD- derived structures results in convergence to the same energy of the structures, with minimal atomic displacements, and good agreement of gauge-included projector augmented wave (GIPAW) calculated and experimentally determined NMR 1H, 13C, and 15N chemical shifts, and 14N quadrupolar parameters. Calculations on isolated molecules combined with 2D magic-angle spinning (MAS) 1H double-quantum (DQ) and 14N–1H NMR experiments confirm the 3D packing arrangement of β-piroxicam. NMR crystallography is shown to be an effective means of validating crystal structures that might otherwise be considered sceptically on the basis of diffraction data alone

Impaired Competence for Pretense in Children with Autism: Exploring Potential Cognitive Predictors.

Lack of pretense in children with autism has been explained by a number of theoretical explanations, including impaired mentalising, impaired response inhibition, and weak central coherence. This study aimed to empirically test each of these theories. Children with autism (n=60) were significantly impaired relative to controls (n=65) when interpreting pretense, thereby supporting a competence deficit hypothesis. They also showed impaired mentalising and response inhibition, but superior local processing indicating weak central coherence. Regression analyses revealed that mentalising significantly and independently predicted pretense. The results are interpreted as supporting the impaired mentalising theory and evidence against competing theories invoking impaired response inhibition or a local processing bias. The results of this study have important implications for treatment and intervention

5-amino-2-methylpyridinium hydrogen fumarate : an XRD and NMR crystallography analysis

Single‐crystal X‐ray diffraction structures of the 5‐amino‐2‐methylpyridinium hydrogen fumarate salt have been solved at 150 and 300 K (CCDC 1952142 and 1952143). A base‐acid‐base‐acid ring is formed through pyridinium‐carboxylate and amine‐carboxylate hydrogen bonds that hold together chains formed from hydrogen‐bonded hydrogen fumarate ions. 1H and 13C chemical shifts as well as 14N shifts that additionally depend on the quadrupolar interaction are determined by experimental magic‐angle spinning (MAS) solid‐state nuclear magnetic resonance (NMR) and gauge‐including projector augmented wave (GIPAW) calculation. Two‐dimensional homonuclear 1H‐1H double‐quantum (DQ) MAS and heteronuclear 1H‐13C and 14N‐1H spectra are presented. Only small differences of up to 0.1 ppm and 0.6 ppm for 1H and 13C are observed between GIPAW calculations starting with the two structures solved at 150 and 300 K (after geometry optimisation of atomic positions, but not unit cell parameters). A comparison of GIPAW calculated 1H chemical shifts for isolated molecules and the full crystal structures is indicative of hydrogen bonding strength

TADPOL: A 1.3 mm Survey of Dust Polarization in Star-forming Cores and Regions

We present {\lambda}1.3 mm CARMA observations of dust polarization toward 30 star-forming cores and 8 star-forming regions from the TADPOL survey. We show maps of all sources, and compare the ~2.5" resolution TADPOL maps with ~20" resolution polarization maps from single-dish submillimeter telescopes. Here we do not attempt to interpret the detailed B-field morphology of each object. Rather, we use average B-field orientations to derive conclusions in a statistical sense from the ensemble of sources, bearing in mind that these average orientations can be quite uncertain. We discuss three main findings: (1) A subset of the sources have consistent magnetic field (B-field) orientations between large (~20") and small (~2.5") scales. Those same sources also tend to have higher fractional polarizations than the sources with inconsistent large-to-small-scale fields. We interpret this to mean that in at least some cases B-fields play a role in regulating the infall of material all the way down to the ~1000 AU scales of protostellar envelopes. (2) Outflows appear to be randomly aligned with B-fields; although, in sources with low polarization fractions there is a hint that outflows are preferentially perpendicular to small-scale B-fields, which suggests that in these sources the fields have been wrapped up by envelope rotation. (3) Finally, even at ~2.5" resolution we see the so-called "polarization hole" effect, where the fractional polarization drops significantly near the total intensity peak. All data are publicly available in the electronic edition of this article.Comment: 53 pages, 37 figures -- main body (13 pp., 3 figures), source maps (32 pp., 34 figures), source descriptions (8 pp.). Accepted by the Astrophysical Journal Supplemen

Polymorph identification for flexible molecules : linear regression analysis of experimental and calculated solution- and solid-state NMR data

The Δδ regression approach of Blade et al. [ J. Phys. Chem. A 2020, 124(43), 8959–8977] for accurately discriminating between solid forms using a combination of experimental solution- and solid-state NMR data with density functional theory (DFT) calculation is here extended to molecules with multiple conformational degrees of freedom, using furosemide polymorphs as an exemplar. As before, the differences in measured 1H and 13C chemical shifts between solution-state NMR and solid-state magic-angle spinning (MAS) NMR (Δδexperimental) are compared to those determined by gauge-including projector augmented wave (GIPAW) calculations (Δδcalculated) by regression analysis and a t-test, allowing the correct furosemide polymorph to be precisely identified. Monte Carlo random sampling is used to calculate solution-state NMR chemical shifts, reducing computation times by avoiding the need to systematically sample the multidimensional conformational landscape that furosemide occupies in solution. The solvent conditions should be chosen to match the molecule’s charge state between the solution and solid states. The Δδ regression approach indicates whether or not correlations between Δδexperimental and Δδcalculated are statistically significant; the approach is differently sensitive to the popular root mean squared error (RMSE) method, being shown to exhibit a much greater dynamic range. An alternative method for estimating solution-state NMR chemical shifts by approximating the measured solution-state dynamic 3D behavior with an ensemble of 54 furosemide crystal structures (polymorphs and cocrystals) from the Cambridge Structural Database (CSD) was also successful in this case, suggesting new avenues for this method that may overcome its current dependency on the prior determination of solution dynamic 3D structures

A Sino-German 6cm polarization survey of the Galactic plane VII. Small supernova remnants

We study the spectral and polarization properties of supernova remnants (SNRs) based on our 6cm survey data. The observations were taken from the Sino-German 6cm polarization survey of the Galactic plane. By using the integrated flux densities at 6cm together with measurements at other wavelengths from the literature we derive the global spectra of 50 SNRs. In addition, we use the observations at 6cm to present the polarization images of 24 SNRs. We derived integrated flux densities at 6cm for 51 small SNRs with angular sizes less than 1 degree. Global radio spectral indices were obtained in all the cases except for Cas A. For SNRs G15.1-1.6, G16.2-2.7, G16.4-0.5, G17.4-2.3, G17.8-2.6, G20.4+0.1, G36.6+2.6, G43.9+1.6, G53.6-2.2, G55.7+3.4, G59.8+1.2, G68.6-1.2, and G113.0+0.2, the spectra have been significantly improved. From our analysis we argue that the object G16.8-1.1 is probably an HII region instead of a SNR. Cas A shows a secular decrease in total intensity, and we measured a flux density of 688+/-35 Jy at 6cm between 2004 and 2008. Polarized emission from 25 SNRs were detected. For G16.2-2.7, G69.7+1.0, G84.2-0.8 and G85.9-0.6, the polarized emission is detected for the first time confirming them as SNRs. High frequency observations of SNRs are rare but important to establish their spectra and trace them in polarization in particular towards the inner Galaxy where Faraday effects are important.Comment: 14 pages, 4 figures, 2 tables, accepted for publication in A&

Pan-Atlantic analysis of the overlap of a highly migratory species, the leatherback turtle, with pelagic longline fisheries

This is the final version of the article. Available from the publisher via the DOI in this record.Large oceanic migrants play important roles in ecosystems, yet many species are of conservation concern as a result of anthropogenic threats, of which incidental capture by fisheries is frequently identified. The last large populations of the leatherback turtle, Dermochelys coriacea, occur in the Atlantic Ocean, but interactions with industrial fisheries could jeopardize recent positive population trends, making bycatch mitigation a priority. Here, we perform the first pan-Atlantic analysis of spatio-temporal distribution of the leatherback turtle and ascertain overlap with longline fishing effort. Data suggest that the Atlantic probably consists of two regional management units: northern and southern (the latter including turtles breeding in South Africa). Although turtles and fisheries show highly diverse distributions, we highlight nine areas of high susceptibility to potential bycatch (four in the northern Atlantic and five in the southern/equatorial Atlantic) that are worthy of further targeted investigation and mitigation. These are reinforced by reports of leatherback bycatch at eight of these sites. International collaborative efforts are needed, especially from nations hosting regions where susceptibility to bycatch is likely to be high within their exclusive economic zone (northern Atlantic: Cape Verde, Gambia, Guinea Bissau, Mauritania, Senegal, Spain, USA and Western Sahara; southern Atlantic: Angola, Brazil, Namibia and UK) and from nations fishing in these high-susceptibility areas, including those located in international waters.Work in Gabon was financially supported by the Large Pelagics Research Center through National Oceanographic and Atmospheric Agency award no. NA04NMF4550391, the UK Defra Darwin Initiative, the Shellshock Campaign (European Association for Zoos and Aquaria) and the UK Natural Environment Research Council. Sea turtle monitoring programmes in Gabon were financially supported by the Wildlife Conservation Society and by the Gabon Sea Turtle Partnership with funding from the Marine Turtle Conservation Fund (United States Fish and Wildlife Service, US Department of the Interior). Four of the satellite tags were deployed in Canadian waters by M. James (Dalhousie University) and the Canadian Sea Turtle Network, with the funding support of Canadian Sea Turtle Network leatherback field research provided by R. A. Myers, the Canadian Wildlife Federation, Environment Canada and WWF-Canada. Work in French Guiana was financially supported by CNES, DEAL and the European Union.This study results from the collaborative effort of 10 data providers, which have satellite-tracked leatherback turtles in the Atlantic Ocean since 1995, through their voluntary participation in the Trans-Atlantic Leatherback Conservation Initiative (TALCIN), a WWF-led initiative. We thank C. Drews (WWF-International) and Jean-Yves Georges (IPHC-CNRS) for having initiated this project. Significant contributions were made by A. Fonseca and M. L. Felix and the WWF Guianas office in fostering this project to secure its continuation. We thank those involved in the sea turtle restoration plan in French Guiana (DEAL, ONCFS, Kulalasi NGO, Kwata, the Reserve Naturelle de l'Amana, Chiefs of Awala and Yalimapo), Yvon Le Maho (IPHC-CNRS) for having initiated the leatherback tracking programme in French Guiana, colleagues from the Regional Program for Sea Turtles Research and Conservation of Argentina–PRICTMA, Aquamarina and Fundación Mundo Marino, the onboard scientific observers from PNOFA-DINARA, the crew and owner of the F/V Torres del Paine, the artisanal fishermen from Kiyú, San José, Uruguay, D. del Bene (PROFAUMA), Z. Di Rienzo and colleagues from Karumbé, the University of Pisa for initiating the satellite tagging programmes in South Africa, and the South African Department of Environmental Affairs for continuing the work in cooperation with Dr Nel from the Nelson Mandela Metropolitan University, Port Elizabeth and Ezemvelo KZN Wildlife. We thank M. L. Felix for her efforts in the deployment of satellite tags in Suriname and the Nature Conservation Division Suriname for facilitating these research efforts. P.M. thanks C. Palma for his help in dealing with ICCAT's database, C. Ere, as well as the GIS training and support received from SCGIS and the ESRI Conservation Program, which allowed processing of fishing-effort data. We thank J. Parezo for her careful reading of the manuscript. All authors designed the study and contributed data; S.F, M.S.C., P.M. and M.J.W. compiled the data; S.F., M.A.N. and A.L. coordinated and supervised the project; S.F., M.J.W., P.M. and B.J.G. led the data analysis and interpretation with contributions from all authors; the manuscript was developed by S.F. and M.J.W. as lead authors, with contributions from all authors