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Background: In patients with end-stage heart failure, durable Left Ventricular Assist Devices (LVADs) can be used as a bridge to transplant or destination therapy. LVADs have been shown to improve survival for patients with heart failure (HF). HF is associated with electrolyte abnormalities and the development of sustained arrhythmias. However, data on the influence of arrhythmias and electrolyte imbalances on inpatient outcomes in LVAD patients are lacking. Furthermore, previous works assessing inpatient outcomes focused mainly on the role of chronic comorbidities in those outcomes. Methods: In this cross-sectional study, we used discharge data from the National Inpatient Sample from 2019 to 2020 to assess the influence of acute arrhythmias on inpatient mortality in patients with LVADs. We also investigated the relationship between acute medical conditions and mortality. Results: There were 9418 (not survey-adjusted) hospitalizations with LVAD, among which 2539 (27%) died during the hospitalization. Univariate analysis of arrhythmias showed that ventricular arrhythmias (VAs)—ventricular fibrillation/flutter and ventricular tachycardia—as well as complete heart block were associated with significantly higher odds of mortality. Follow-up multivariable logistic analysis showed that these arrhythmias retain their increased association with death. Hyperkalemia and acidosis had increased adjusted odds of death (1.54 (95% confidence interval: 1.28–1.85) (p < 0.001) and 2.44 (CI: 2.14–2.77) (p < 0.001), respectively). Conclusions: VAs, complete heart block, hyperkalemia, and acidosis were associated with increased odds of all-cause mortality. Females had higher odds of inpatient mortality. These findings suggest that electrolyte management, maintenance of optimal acid–base balance, and interventions to treat sustained ventricular arrhythmias may be suitable therapeutic targets to reduce mortality in hospitalized patients with LVADs. [ABSTRACT FROM AUTHOR]

Lithium salts continue to find pharmaceutical applications, particularly as psychiatric medications. As with any active pharmaceutical ingredient, structural polymorphism is an important concern for lithium-based medications that can influence solubility and other physicochemical properties. Here we report a 13C, 1H, and 7Li magic-angle spinning solid-state nuclear magnetic resonance (MAS SSNMR) study of two 1:1 polymorphic ionic cocrystals of lithium 4-methoxybenzoate and L-proline (L4MPRO(α) and L4MPRO(β)). One-dimensional 13C cross-polarization MAS and two-dimensional heteronuclear correlation NMR spectra hint at differential mobilities of the proline and benzoate moieties for the two polymorphs. Five key resonances differ in 13C chemical shift by more than 1 ppm between the two polymorphs, clearly distinguishing between them. Gauge-including projector-augmented-wave density functional theory calculations of 13C and 1H magnetic shielding constants correlate strongly with the experimental chemical shifts for both polymorphs. R2 and root-mean-square deviation metrics are shown to be insufficient in the case of 13C, but sufficient in the case of 1H, for differentiating between the polymorphs. 7Li satellite-transition MAS NMR of both polymorphs are identical, as are the computed lithium magnetic shielding constants, demonstrating the insensitivity of 7Li NMR to polymorphism in these samples. This work highlights the utility of solid-state NMR spectroscopy for examining ionic salt cocrystals and also highlights some caveats in this regard. [ABSTRACT FROM AUTHOR]

Ameloblastic carcinoma is a locally aggressive odontogenic tumor that most commonly affects young and middle-aged adults. Metastatic disease may develop insidiously and manifest months or years after the initial diagnosis. Herein, we describe the clinical, imaging, and pathologic findings of a 31-year-old male who presented to the emergency department with headache and vision loss of 3 months duration and was subsequently found to have ameloblastic carcinoma with hepatic metastases. Initial computed tomography (CT) and magnetic resonance imaging revealed a multilocular cystic mass with avidly-enhancing nodular soft-tissue components associated with the right temporal fossa. Histologic examination of a tissue sample showed findings consistent with ameloblastic carcinoma. An initial staging CT scan showed several small hepatic cystic lesions. Follow-up surveillance imaging showed interval growth. A subsequent biopsy of a hepatic lesion showed findings compatible with metastatic ameloblastic carcinoma. The patient was started on systemic chemotherapy with evidence of disease progression at 1-year follow-up. [ABSTRACT FROM AUTHOR]

Diffuse large B‐cell lymphoma often presents with extranodal manifestations involving the musculoskeletal system. Shoulder pain is particularly worrisome for malignancy. Individuals presenting with refractory upper extremity complaints should undergo a prompt and thorough evaluation for cancer, as a delay in diagnosis can result in an unfavorable outcome. [ABSTRACT FROM AUTHOR]

This article describes some highlights of the research which has been carried out in my laboratory at the University of Ottawa over the period covering 2005 to 2014. My research is in the general areas of solid-state NMR, applications of quantum chemistry, and biomolecular NMR. The format will follow that of my 2014 Canadian Society for Chemistry Keith Laidler Award presentation given in Vancouver in June 2014 at the 97th Canadian Chemistry Conference and Exhibition. Following a brief introduction, I will present some of our most interesting and exciting recent advances according to the following six themes: 1. Fundamental solid-state NMR. 2. Materials characterization and NMR crystallography. 3. Pharmaceuticals and polymorphism. 4. Non-covalent interactions: Halogen bonds. 5. Biomolecular NMR. 6. Software development. [ABSTRACT FROM AUTHOR]

Three novel chalcogen‐bonded cocrystals featuring 3,4‐dicyano‐1,2,5‐selenodiazole (C4N4Se) or 3,4‐dicyano‐1,2,5‐tellurodiazole (C4N4Te) as chalcogen‐bond donors and hydroquinone (C6H6O2), tetraphenylphosphonium chloride (C24H20P+·Cl−) or tetraethylphosphonium chloride (C8H20P+·Cl−) as chalcogen‐bond acceptors have been prepared and characterized by single‐crystal X‐ray diffraction (XRD), powder X‐ray diffraction and 77Se/125Te magic‐angle spinning solid‐state NMR spectroscopy. The single‐crystal XRD results show that the chalcogenodiazole molecules interact with the electron donors through two σ‐holes on each of the chalcogen atoms, which results in highly directional and moderately strong chalcogen bonds. Powder XRD confirms that the crystalline phases are preserved upon moderate grinding of the samples for solid‐state NMR experiments. Measurement of 77Se and 125Te chemical shift tensors via magic‐angle spinning solid‐state NMR spectroscopy confirms the number of magnetically unique chalcogen sites in each asymmetric unit and reveals the impact of chalcogen‐bond formation on the local electronic structure. These NMR data are further assessed in the context of analogous data for a wider range of crystalline chalcogen‐bonded systems. [ABSTRACT FROM AUTHOR]

The group 2 metal halides and corresponding metal halide hydrates serve as useful model systems for understanding the relationship between the electric field gradient (EFG) and chemical shift (CS) tensors at the halogen nuclei and the local molecular and electronic structure. Here, we present a 35/37Cl and 43Ca solid-state nuclear magnetic resonance (SSNMR) study of CaCl2. The 35Cl nuclear quadrupole coupling constant, 8.82(8) MHz, and the isotropic chlorine CS, 105(8) ppm (with respect to dilute NaCl(aq)), are different from the values reported previously for this compound, as well as those reported for CaCl2·2H2O. Chlorine-35 SSNMR spectra are also presented for CaCl2·6H2O, and when taken in concert, the SSNMR observations for CaCl2, CaCl2·2H2O, and CaCl2·6H2O clearly demonstrate the sensitivity of the chlorine EFG and CS tensors to the local symmetry and to changes in the hydration state. For example, the value of δiso decreases with increasing hydration. Gauge-including projector-augmented wave (GIPAW) density functional theory (DFT) calculations are used to substantiate the experimental SSNMR findings, to rule out the presence of other hydrates in our samples, to refine the hydrogen positions in CaCl2·2H2O, and to explore the isostructural relationship between CaCl2 and CaBr2. Finally, the 43Ca CS tensor span is measured to be 31(5) ppm for anhydrous CaCl2, which represents only the fifth CS tensor span measurement for calcium. [ABSTRACT FROM AUTHOR]

Zeroth-order regular approximation (ZORA) density functional theory (DFT) calculations of one-bond X-19F indirect nuclear spin-spin coupling ( J) tensors were performed on a series of fluorine-containing compounds covering several valence shell electron pair repulsion (VSEPR) theory geometries for which J, by symmetry, is not required to be axially symmetric. The calculations show that the antisymmetric components of J are only of the same order of magnitude as the principal components of the symmetric J-coupling tensor for a few geometries, and that in cases of approximate axial symmetry along the bond, J remains nearly axially symmetric with its unique component along the bond. In general, different species having the same nominal geometry tend to have similar tensor orientations, magnitudes of anisotropy of J relative to the isotropic coupling constant, as well as the same dominant contributions from the different coupling mechanisms. Structures are also systematically modified to determine how the tensor components depend on geometrical parameters. The isotropic coupling constants are subsequently interpreted using a natural localized molecular orbital (NLMO) approach. Our results could prove to be useful for future experimental characterizations of J tensors in systems having symmetry properties that do not force J to be axially symmetric or coincident with the dipolar coupling tensor. [ABSTRACT FROM AUTHOR]

NMR parameters such as indirect nuclear spin–spin coupling (J), nuclear magnetic shielding (σ), direct dipolar coupling (D), and electric field gradient (V) are properly described by second-rank tensors. Each may be decomposed into isotropic, symmetric, and antisymmetric components; the number of these three components which may be nonzero is a distinguishing attribute of each interaction tensor. The rank-1 antisymmetric portion of J (Janti) holds the distinction of remaining the only nonzero part of these fundamental NMR interaction tensors which has never been observed experimentally. Accordingly, effects from Janti are usually ignored, but it is important to consider when this is valid. An experimental strategy for observing Janti in powdered samples of tightly coupled homonuclear spin pairs, based on ideas originally presented by Andrew and Farnell (Mol. Phys. 1968, 15, 157), is described. The theory of Andrew and Farnell is extended to powder samples, and methods for analyzing NMR spectra from powdered samples are presented. It is found that, in certain rare cases, Janti has the potential to affect the NMR line shapes from AB spin systems, but that even in these systems, the most intense features of the spectra are not affected and may be analyzed independently of Janti. Furthermore, Janti will only have an observable effect on the NMR spectra when its magnitude is comparable with that of Jiso and with the difference in chemical shifts (in Hz) between the two sites. Finally, the first experimental attempts to measure Janti are reported, and experimental proof that no elements of Janti(119Sn,119Sn) in hexa(p-tolyl)ditin are larger than 2900 Hz is given. The benefits of modern double-quantum filtering NMR pulse sequences in isolating effects from Janti are also illustrated. [ABSTRACT FROM AUTHOR]

The accurate calculation of the isotropic (Jiso) and anisotropic (ΔJ) parts of indirect nuclear spin–spin coupling tensors is a stringent test for quantum chemistry, particularly for couplings involving heavy isotopes where relativistic effects and relativity – electron correlation cross terms are expected to play an important role. Experimental measurements on diatomic molecules in the gas phase offer ideal data for testing the success of computational approaches, since the data are essentially free from intermolecular effects, and precise coupling anisotropies may be reliably extracted in favourable cases. On the basis of available experimental molecular-beam coupling-tensor parameters for diatomic alkali metal halides, we tabulate known values of Jiso and, taking rotational–vibrational corrections to the direct dipolar coupling constant into account, precise values of ΔJ are determined for the ground rovibrational state. First-principles calculations of the coupling tensors were performed using a recently developed program based on hybrid density functional theory using the two-component relativistic zeroth-order regular approximation (ZORA). Experimental trends in Jiso and ΔJ are reproduced with correlation coefficients of 0.993 and 0.977, respectively. Periodic trends in the coupling constants and their dependence on the product of the atomic numbers of the coupled nuclei are discussed. Finally, the hybrid functional method is also successfully tested against experimental data for a series of polyatomic xenon fluorides and group-17 fluorides. [ABSTRACT FROM AUTHOR]

Coronavirus disease 2019 (COVID-19) represents a major challenge in the management of patients with hematologic malignancies. Individuals with plasma cell dyscrasias, including multiple myeloma, are at increased risk of developing severe disease. Furthermore, immunosuppressant agents, which represent an important component of multiple myeloma treatment, may increase the risk of serious infection; thus, treatment regimens may need to be modified in some patients. The pathogenesis of COVID-19 is incompletely understood and much remains to be established regarding cancer care in the setting of this new global health threat. We report a case of multiple myeloma remission that occurred after a single cycle of chemotherapy in a patient with COVID-19. In addition, we discuss possible mechanisms underlying this surprising observation. The findings warrant further investigation and may have important implications for the management of multiple myeloma and other plasma cell dyscrasias in the age of COVID-19. [ABSTRACT FROM AUTHOR]

The article presents profile of scientist John Ripmeester. Topics include his enrollment at the University of British Columbia where he came across nuclear magnetic resonance (NMR) NMR spectroscopy; joining the Division of Chemistry at the U.S. National Research Council along with scientist Don Davidson; and his focus on clathrate hydrate research after his retirement.

The article features scientist John Ripmeester, who has made enormous impact on various research areas involving nuclear magnetic resonance (NMR) spectroscopy, porous materials, and clathrate hydrates. Topics include Ripmeester's experience of working for the paper industry in Canada, how his interest in chemistry has been developed, and his retirement from research in 2008 to focus on his role as head of the Functional Materials Program of the Steacie Institute for Molecular Sciences (SIMS).

David Bryce and Francis Taulelle introduce this special issue of Acta Crystallographica Section C on `NMR Crystallography' where the contributions serve as an excellent introduction to the power and scope of NMR crystallographic methods and applications. [ABSTRACT FROM AUTHOR]

The concept of variable stoichiometry cocrystallization is explored in halogen-bonded systems. Three novel cocrystals of 1,4-diiodotetrafluorobenzene and 3-nitropyridine with molar ratios of 1:1, 2:1, and 1:2, respectively, are prepared by slow evaporation methods. Single-crystal X-ray diffraction analysis reveals key differences between each of the nominally similar cocrystals. For instance, the 1:1 cocrystal crystallizes in the P21/n space group and features a single chemically and crystallographically unique halogen bond between iodine and the pyridyl nitrogen. The 2:1 cocrystal crystallizes in the --> P 1 ¯ --> space group and features a halogen bond between iodine and one of the nitro oxygens in addition to an iodine–nitrogen halogen bond. The 1:2 cocrystal crystallizes with a large unit cell (V = 9896 Å3) in the Cc space group and features 10 crystallographically distinct iodine-nitrogen halogen bonds. Powder X-ray diffraction experiments carried out on the 1:1 and 2:1 cocrystals confirm that gentle grinding does not alter the crystal forms. 1H → 13C and 19F → 13C cross-polarization magic angle spinning (CP/MAS) NMR experiments performed on powdered samples of the 1:1 and 2:1 cocrystals are used as spectral editing tools to select for either the halogen bond acceptor or donor, respectively. Carbon-13 chemical shifts in the cocrystals are shown to change only very subtly relative to pure solid 1,4-diiodotetrafluorobenzene, but the shift of the carbon directly bonded to iodine nevertheless increases, consistent with halogen bond formation (e.g., a shift of +1.6 ppm for the 2:1 cocrystal). This work contributes new examples to the field of variable stoichiometry cocrystal engineering with halogen bonds. [ABSTRACT FROM AUTHOR]

Sodium valproate is a pharmaceutical with applications in the treatment of epilepsy, bipolar disorder, and other ailments. Sodium valproate can exist in many hydrated and acid-stabilized forms in the solid state, and it can be difficult to obtain precise structural information about many of these. Here, we present a 13C and 23Na solid-state NMR study of several forms of sodium valproate, only one of which has been previously structurally characterized by single-crystal X-ray diffraction. 23Na magic-angle spinning (MAS), double-rotation (DOR), and multiple-quantum magic-angle spinning (MQMAS) NMR spectra are shown to provide useful information on the number of molecules in the asymmetric unit, the local coordination geometry of the sodium cations, and the presence of amorphous phases. Two previously identified forms are shown to be highly similar, or identical, according to the 23Na NMR data. The utility of carrying out both DOR and MQMAS NMR experiments to identify all crystallographically unique sites is demonstrated. 13C cross-polarization MAS NMR spectra also provide complementary information on the number of molecules in the asymmetric unit and the crystallinity of the sample. [ABSTRACT FROM AUTHOR]

A highly cross-linked microporous organic network with imine linkers was prepared by condensation of tetrakis(4-aminophenyl)methane with terephthaldehyde. Gas adsorption studies indicate that the material exhibits permanent microporosity, and guest exchange experiments demonstrate that small molecules can diffuse into the network. Postsynthetic modification of this microporous network was achieved by treatment with borane in THF, which reduced the imine groups to the corresponding amines as shown by IR and 13C CP-MAS solid-state NMR spectroscopy. The resulting material showed enhanced resistance to acidic hydrolysis compared with the imine precursor, and retained its ability to absorb guest molecules. The amine network was amenable to further postsynthetic modifications. Specifically, acetylation of this network using acetic anhydride was demonstrated. [ABSTRACT FROM AUTHOR]

A computer program (EFGShield) is described that simplifies and summarizes the output from electric field gradient (EFG) and nuclear magnetic shielding tensor calculations performed independently using existing quantum chemical software. In addition to summarizing tensor magnitudes according to conventions commonly used by solid-state NMR spectroscopists, the program provides Euler angles relating the orientations of the EFG and shielding tensor principal axis systems (PAS). An atomic coordinate file is generated that also contains dummy atoms representing the orientations of the EFG and shielding tensor PASs in the molecular framework. We demonstrate the functionality of the program using calculations of the chlorine EFG and shielding tensors for strontium chloride dihydrate and calcium chloride dihydrate. Several models of the chloride environment in these compounds are tested, including those where point charges are used to represent the extended three-dimensional lattices within the self-consistent charge field perturbation approach. The results highlight both the shortcomings and successes of traditional localized orbital-based basis sets in the description of the NMR properties of extended systems. We anticipate that EFGShield will be a useful tool for spectroscopists using quantum chemical software to aid in the interpretation of experimental data. [ABSTRACT FROM AUTHOR]

The halogen bond has previously been explored as a versatile tool in crystal engineering and anion coordination chemistry, with mechanochemical synthetic techniques having been shown to provide convenient routes towards cocrystals. In an effort to expand our knowledge on the role of halogen bonding in anion coordination, here we explore a series of cocrystals formed between 3‐iodoethynylpyridine and 3‐iodoethynylbenzoic acid with halide salts. In total, we report the single‐crystal X‐ray structures of six new cocrystals prepared by mechanochemical ball milling, with all structures exhibiting C≡C−I⋅⋅⋅X− (X=Cl, Br) halogen bonds. Whereas cocrystals featuring a pyridine group favoured the formation of discrete entities, cocrystals featuring a benzoic acid group yielded an alternation of halogen and hydrogen bonds. The compounds studied herein were further characterized by 13C and 31P solid‐state nuclear magnetic resonance, with the chemical shifts offering a clear and convenient method of identifying the occurrence of halogen bonding, using the crude product obtained directly from the mechanochemical ball milling. Whereas the 31P chemical shifts were quickly able to identify the occurrence of cocrystallization, 13C solid‐state NMR was diagnostic of both the occurrence of halogen bonding and of hydrogen bonding. [ABSTRACT FROM AUTHOR]

Nepheline (Na6K2Al8Si8O32) is a rock-forming tectosilicate mineral which is by far the most abundant of the feldspathoids. The crystallization in nepheline-based glass-ceramics proceeds through several polymorphic transformations - mainly orthorhombic, hexagonal, cubic - depending on their thermochemistry. However, the fundamental science governing these transformations is poorly understood. In this article, an attempt has been made to elucidate the structural drivers controlling these polymorphic transformations in nepheline-based glass-ceramics. Accordingly, two different sets of glasses (meta-aluminous and per-alkaline) have been designed in the system Na2O-CaO-Al2O3-SiO2 in the crystallization field of nepheline and synthesized by the melt-quench technique. The detailed structural analysis of glasses has been performed by 29Si, 27Al, and 23Na magic-angle spinning - nuclear magnetic resonance ( MAS NMR), and multiple-quantum MAS NMR spectroscopy, while the crystalline phase transformations in these glasses have been studied under isothermal and non-isothermal conditions using differential scanning calorimetry ( DSC), X-ray diffraction ( XRD), and MQMAS NMR. Results indicate that the sequence of polymorphic phase transformations in these glass-ceramics is dictated by the compositional chemistry of the parent glasses and the local environments of different species in the glass structure; for example, the sodium environment in glasses became highly ordered with decreasing Na2O/CaO ratio, thus favoring the formation of hexagonal nepheline, while the cubic polymorph was the stable phase in SiO2-poor glass-ceramics with (Na2O+CaO)/Al2O3 > 1. The structural origins of these crystalline phase transformations have been discussed in the paper. [ABSTRACT FROM AUTHOR]

Halogen bonding is a noncovalent interaction between the electrophilic region of a halogen (σ-hole) and an electron donor. We report a crystallographic and structural analysis of halogen-bonded compounds by applying a combined X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (SSNMR) approach. Single-crystal XRD was first used to characterize the halogen-bonded cocrystals formed between two fluorinated halogen-bond donors (1,4-diiodotetrafluorobenzene and 1,3,5-trifluoro-2,4,6-triiodobenzene) and several nitrogen-containing heterocycles (acridine, 1,10-phenanthroline, 2,3,5,6-tetramethylpyrazine, and hexamethylenetetramine). New structures are reported for the following three cocrystals, all in the P21/ c space group: acridine-1,3,5-trifluoro-2,4,6-triiodobenzene (1/1), C6F3I3·C13H9N, 1,10-phenanthroline-1,3,5-trifluoro-2,4,6-triiodobenzene (1/1), C6F3I3·C12H8N2, and 2,3,5,6-tetramethylpyrazine-1,3,5-trifluoro-2,4,6-triiodobenzene (1/1), C6F3I3·C8H12N2. 13C and 19F solid-state magic-angle spinning (MAS) NMR is shown to be a convenient method to characterize the structural features of the halogen-bond donor and acceptor, with chemical shifts attributable to cocrystal formation observed in the spectra of both nuclides. Cross polarization (CP) from 19F to 13C results in improved spectral sensitivity in characterizing the perfluorinated halogen-bond donor when compared to conventional 1H CP. Gauge-including projector-augmented wave density functional theory (GIPAW DFT) calculations of magnetic shielding constants, along with optimization of the XRD structures, provide a final set of structures in best agreement with the experimental 13C and 19F chemical shifts. Data for carbons bonded to iodine remain outliers due to well-known relativistic effects. [ABSTRACT FROM AUTHOR]

17O solid-state NMR studies of waters of hydration in crystalline solids are presented. The 17O quadrupolar coupling and chemical shift (CS) tensors, and their relative orientations, are measured experimentally at room temperature for α-oxalic acid dihydrate, barium chlorate monohydrate, lithium sulfate monohydrate, potassium oxalate monohydrate, and sodium perchlorate monohydrate. The 17O quadrupolar coupling constants ( CQ) range from 6.6 to 7.35 MHz and the isotropic chemical shifts range from -17 to 19.7 ppm. The oxygen CS tensor spans vary from 25 to 78 ppm. These represent the first complete CS and electric field gradient tensor measurements for water coordinated to metals in the solid state. Gauge-including projector-augmented wave density functional theory calculations overestimate the values of CQ, likely due to librational dynamics of the water molecules. Computed CS tensors only qualitatively match the experimental data. The lack of strong correlations between the experimental and computed data, and between these data and any single structural feature, is attributed to motion of the water molecules and to the relatively small overall range in the NMR parameters relative to their measurement precision. Nevertheless, the isotropic chemical shift, quadrupolar coupling constant, and CS tensor span clearly differentiate between the samples studied and establish a 'fingerprint' 17O spectral region for water coordinated to metals in solids. [ABSTRACT FROM AUTHOR]

A thorough investigation of solid-state NMR signal enhancement schemes and high-resolution techniques for application to the spin-7/2 43Ca nuclide are presented. Signal enhancement experiments employing double frequency sweeps, hyperbolic secant pulses, and rotor-assisted population transfer, which manipulate the satellite transitions of half-integer quadrupolar nuclei to polarize the central transition (m = +1/2 ... -1/2), are carried out on four well-characterized 43Ca isotopically enriched calcium salts: Ca(NO3)2, Ca(OD)2, CaSO4-2H2O, and Ca(OAc)2-H2O. These results, in conjunction with numerical simulations of 43Ca NMR spectra under magic-angle spinning conditions, are used to identify the technique that provides the most uniform (or quantitative) polarization enhancement as well as the largest signal enhancement factors independent of size of the 43Ca quadrupolar coupling constant, which is the most significant source of resonance broadening in 43Ca NMR spectra. These samples are further investigated using 43Ca double-rotation NMR spectroscopy to yield isotropic, or solution-like, NMR spectra with exquisite resolution. In addition, three unique calcium sites are resolved for the hemihydrated form of calcium acetate (unknown structure), Ca(OAc)2-0.5H2O, with double-rotation NMR, whereas the more common, but more time-consuming, multiple quantum magic-angle spinning technique only clearly resolves two calcium sites. The results shown herein will be useful for other NMR spectroscopists attempting to acquire 43Ca solid-state NMR data for unknown and more complex materials with a higher degree of both sensitivity and resolution. [ABSTRACT FROM AUTHOR]

The results of a 35/37Cl solid-state nuclear magnetic resonance (SSNMR) study of the 1-butyl-3-methylimidazolium chloride complex of meso-octamethylcalix[4]pyrrole ( 1) are reported. Line shapes obtained from magic-angle-spinning and stationary powder samples collected at 9.4 and 21.1 T are analyzed to provide the 35/37Cl quadrupolar tensor and chemical shift (CS) tensor and their relative orientation. The relatively high symmetry of the chloride ion coordination environment is manifested in the small value of the quadrupole coupling constant, CQ(35Cl) = 1.0 MHz. The isotropic chemical shift of 120 ppm (with respect to NaCl(s)) is at the upper edge of the typical range seen for organic hydrochlorides. Consideration of chemical shift anisotropy (span, Ω = 50 ppm) and non-coincidence of the quadrupolar and CS tensors were essential to properly simulate the experimental spectra. The utility of gauge-including projector-augmented wave density functional theory (GIPAW-DFT) calculations of chlorine quadrupolar and CS tensors in organic chlorides was explored by validation against available benchmark experimental data for solid amino acid hydrochlorides. The calculations are shown to systematically overestimate the value of the 35Cl quadrupole coupling constant. Additional calculations on various hydrated and solvated models of 1 are consistent with a structure in which solvent and water of hydration are absent. [ABSTRACT FROM AUTHOR]

Transactivation-response element (TAR) is a stable stem-loop structure of HIV RNA, which plays a crucial role during the life cycle of the virus. The apical loop of TAR acts as a binding site for essential cellular cofactors required for the replication of HIV. High-affinity aptamers directed against the apical loop of TAR have been identified by the SELEX approach. The RNA aptamers with the highest affinity for TAR fold as hairpins and form kissing complexes with the targeted RNA through loop-loop interactions. The aptamers with the strongest binding properties all possess a GA base pair combination at the loop-closing position. Using liquid-crystal NMR methodology, we have obtained a structural model in solution of a TAR-aptamer kissing complex with an unprecedented accuracy. This high-resolution structure reveals that the GA base pair is unilaterally shifted toward the 5′ strand and is stabilized by a network of intersugar hydrogen bonds. This specific conformation of the GA base pair allows for the formation of two supplementary stable base-pair interactions. By systematic permutations of the loop-closing base pair, we establish that the identified atomic interactions, which form the basis for the high stability of the complex, are maintained in several other kissing complexes. This study rationalizes the stabilizing role of the loop-closing GA base pairs in kissing complexes and may help the development or improvement of drugs against RNA loops of viruses or pathogens as well as the conception of biochemical tools targeting RNA hairpins involved in important biological functions. [ABSTRACT FROM AUTHOR]

Keywords: halogen bonding; hydrogen bonding; solid-state NMR; crystal engineering; X-ray crystallography The identity and phase purity of this and five related anion-coordinated architectures based on 3-iodoethynylpyridine and 3-iodoethynylbenzoic acid halogen bond donors are established with powder X-ray diffraction and multinuclear solid-state magnetic resonance spectroscopy. Halogen bonding, hydrogen bonding, solid-state NMR, crystal engineering, X-ray crystallography. [Extracted from the article]

Invited for this month's cover picture is the group of Professor David Bryce at the University of Ottawa. The cover picture shows a stylized depiction of the mechanochemical halogen‐bond induced cocrystallization of 3‐iodoethynylpyridine with tetraphenylphosphonium bromide. Read the full text of their Full Paper at 10.1002/open.201900194. [ABSTRACT FROM AUTHOR]

5–15% of cancer patients have unrelieved pain or undesirable side effects despite current best management. IDDS may give better pain control and fewer side effects but there are no randomized clinical trials (RCT). A RCT of IDDS plus CMM vs. CMM alone in patients with unrelieved pain (>5 on 0–10 scale) despite current best management is in progress. The IDDS is the SynchroMed Implantable Drug Delivery System. Outcomes include pain control, quality of life (Brief Pain Inventory, SF-12, Caregiver Quality of Life Survey), and toxicity (National Cancer Institute Common Toxicity Criteria), Health resource utilization data will assess if avoided pain therapy expenditures balance IDDS cost. The study can detect a 20% difference in pain control and toxicity with a target accrual of 200 patients. Over 100 patients have been accrued at 19 centers in 5 countries. The study arms are balanced with respect to pain intensity (VAS), life expectancy, demographic variables, source of cancer pain, and baseline opioid use vs. unacceptable opioid side effects. An interim analysis will present data on patient baseline characteristics; management course at different centers; and effect of therapy on pain scores, quality of life, toxicity, and resource utilization. [ABSTRACT FROM AUTHOR]