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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.

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 [P2.sub.1]/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 P1 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 [A.sup.3]) 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. [.sup.1]H [right arrow] [.sup.13]C and [.sup.19]F [right arrow] [.sup.13]C 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. Key words: solid-state NMR, X-ray diffraction, halogen bond, cocrystal, polymorphism, stoichiometry, stoichiomorphism. Nous avons etudie le concept de cocristallisation a stoechiometrie variable dans des systemes a liaison halogene. Nous avons prepare par evaporation lente trois nouveaux cocristaux de 1,4-diiodotetrafluorobenzene et de 3-nitropyridine avec des rapports molaires de 1:1, de 2:1 et de 1:2, respectivement. L&apos;analyse par diffraction des rayons X sur monocristal revele des differences importantes entre les cocristaux theoriquement similaires. Par exemple, le cocrystal 1:1 cristallise selon le groupe d&apos;espace [P2.sub.1]/n et presente une seule liaison halogene, sur les plans chimique et cristallographique, entre l&apos;iode et l&apos;azote du groupe pyridyle. Le cocrystal 2:1 cristallise selon le groupe d&apos;espace P1 et presente une liaison halogene entre l&apos;iode et l&apos;un des oxygenes du groupe nitro, en plus de la liaison halogene iode-azote. Le cocristal 1:2 cristallise en formant une grande cellule unitaire (V = 9896 [A.sup.3]) selon le groupe d&apos;espace Cc et presente 10 liaisons halogene iode-azote distinctes sur le plan cristallographique. Des experiences de diffraction des rayons X sur poudre realisees sur les cocristaux 1:1 et 2:1 confirment qu&apos;un broyage leger ne modifie pas les formes cristallines. Nous avons utilise des experiences de RMN [.sup.1]H [right arrow] [.sup.13]C et [.sup.19]F [right arrow] [.sup.13]C a polarisation croisee en rotation a l&apos;angle magique (CP/MAS, cross-polarization/magic angle spinning), realisees sur des echantillons de cocristaux 1:1 et 2:1 sous forme de poudre, comme outils d&apos;edition spectrale pour selectionner l&apos;accepteur ou le donneur de liaison halogene, respectivement. Les deplacements chimiques du carbone-13 dans les cocris-taux ne changent que de facon tres subtile par rapport au 1,4-diiodotetrafluorobenzene solide pur, mais le deplacement du carbone directement lie a l&apos;iode augmente neanmoins, ce qui concorde avec la formation de liaisons halogene (p. ex., un deplacement de +1,6 ppm dans le cas du cocrystal 2:1). Ces travaux apportent de nouveaux exemples au domaine de l&apos;ingenierie des cocristaux a stoechiometrie variable comportant des liaisons halogene. [Traduit par la Redaction] Mots-cles : RMN a l&apos;etat solide, diffraction des rayons X, liaison halogene, cocristal, polymorphisme, stoechiometrie, stoechiomorphisme., Introduction Molecular and ionic solids can adopt a range of forms depending on how they are prepared. (1,2) Such forms include pure crystalline or amorphous phases, hydrates, or solvates. In [...]

Users of the microbond test assume that a microbond resin droplet’s properties are equivalent to a macroscale specimen. However, there is currently no standardised methodology for determining the cure state of droplet specimens used in the microbond test. In this paper, we present a technique for microbond test users to better understand the properties of thermoset droplet specimens. Utilising a conventional benchtop spectrometer, a novel sample preparation technique involving curing epoxy droplets on thin-steel filaments allowed for high-throughput determination of the microbond droplet cure state. The parity between steel filament and glass fibre microbond samples was confirmed by infrared microspectroscopy. It is shown that cure schedules used in manufacturing composite parts produced microbond droplets with degrees of cure lower than that of bulk matrix specimens subjected to an identical thermal history. Testable microbond droplets could only be prepared for commercial resin systems when introducing a room temperature pre-curing time of at least 2 h. It is concluded that microbond testing should be supported by some droplet cure state characterisation methods to ensure that interfacial effects are not artefacts of droplet sample preparation. [ABSTRACT FROM AUTHOR]

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]

A pair of novel polymorphic ionic cocrystals of 3,4‐dicyanotelluradiazole and tetraphenylphosphonium bromide are synthesized and are characterized by single‐crystal XRD. Strong and directional non‐covalent chalcogen bonds (ChB) between Te and Br are analyzed via solid‐state NMR to reveal large and anisotropic J(125Te,79/81Br) coupling tensors, providing unequivocal evidence for non‐Fermi contact contributions across ChBs. Along with large 79/81Br quadrupolar couplings for the Br− anions, these data provide new tools to characterize chalcogen bonds and to differentiate between ChB polymorphs. [ABSTRACT FROM AUTHOR]

Cerebral artery aneurysms are present in up to 10% of ischemic stroke patients, often within or adjacent to the occluded vessel. In some cases, the approach to intervention may need to be modified based on the size and location of the aneurysm. We describe a 99-year-old female with a known history of cerebral aneurysm who underwent successfully mechanical thrombectomy of a right middle cerebral artery thrombus; an 8-mm aneurysm involving the right M1 bifurcation was identified only on post-procedural digital subtraction angiography. In addition, we discuss strategies to reduce the risk of iatrogenic aneurysm rupture in the setting of endovascular thrombectomy.

Abstract 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.

This recommendation proposes a definition for the term "pnictogen bond"; the term pnictogen bond designates a subset of the attractive interactions between an electrophilic region on a pnictogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. [ABSTRACT FROM AUTHOR]

Matere bonds (MaB) to rhenium in a set of organic perrhenates are probed via185/187Re solid-state NMR in applied magnetic fields of up to 35.2 T, and via185/187Re NQR. 185/187Re quadrupolar couplings distinguish between MaB samples and control samples, and their precise values are governed by shear strain of the ReO4− anions. [ABSTRACT FROM AUTHOR]

Macrocycle formation that relies upon trans metal coordination of appropriately placed pyridine ligands within an arylene ethynylene construct provides rapid and reliable access to molecular rotators encapsulated within macrocyclic stators. Showing no significant close contacts to the central rotators, X‐ray crystallography of AgI‐coordinated macrocycles provides plausibility for unobstructed rotation or wobbling of rotators within the central cavity. Solid‐state 13C NMR of PdII‐coordinated macrocycles supports the notion of unobstructed movement of simple arenes in the crystal lattice. Solution 1H NMR studies indicate complete and immediate macrocycle formation upon the introduction of PdII to the pyridyl‐based ligand at room temperature. Moreover, the formed macrocycle is stable in solution; a lack of significant changes in the 1H NMR spectrum upon cooling to −50 °C is consistent with the absence of dynamic behavior. The synthetic route to these macrocycles is expedient and modular, providing access to rather complex constructs in four simple steps involving Sonogashira coupling and deprotection reactions. [ABSTRACT FROM AUTHOR]

The first example of a binary cocrystal, comprised of SnPh3Cl and PPh3, whose components are organized via short and directional tetrel bonds (TtB) between tin and phosphorus, is described. DFT elucidates, for the first time, the factors influencing the strength of TtBs involving heavy pnictogens. A CSD survey reveals that such TtBs are also present and determinative in single component molecular systems, highlighting their significant potential as tuneable structure-directing elements. [ABSTRACT FROM AUTHOR]

Phenomena such as anticooperativity and competition among non‐covalent bond donors and acceptors are key considerations when exploring the polymorphic and stoichiomorphic landscapes of binary and higher‐order cocrystalline architectures. We describe the preparation of four cocrystals of 1,3,5‐trifluoro‐2,4,6‐triiodobenzene with N‐heterocyclic compounds, namely acridine, 3‐aminopyridine, 4‐methylaminopyridine, and 1,2‐di(4‐pyridyl)ethane. The cocrystals, which are characterized by single‐crystal and powder X‐ray diffraction experiments, all show moderately strong and directional iodine⋅⋅⋅nitrogen halogen bonds with reduced distance parameters ranging from 0.79 to 0.92 and carbon‐iodine⋅⋅⋅nitrogen bond angles ranging from 165.4(3) to 175.31(7)°. The cocrystal comprising 1,3,5‐trifluoro‐2,4,6‐triiodobenzene and acridine provides a relatively rare example where all three halogen bond donor sites form halogen bonds with three acceptor molecules, overcoming an anticooperative effect. This effect manifests itself through the lengthening of non‐halogen‐bonded C−I bonds, weakening their potential to form halogen bonds. The effect is only observed once two halogen bonds have been formed to 1,3,5‐trifluoro‐2,4,6‐triiodobenzene; one such bond does not appear to be adequate. Among the four cocrystals studied, competition between the pyridyl nitrogen atoms and the amine nitrogen atoms suggests that the former are the preferred halogen bond acceptors. Analysis by Hirshfeld fingerprint plots and 13C and 19F magic‐angle spinning solid‐state nuclear magnetic resonance (NMR) spectroscopy provides additional insights into the prevalence of various short contacts in the crystal structures and into the spectral response to halogen‐bond‐induced cocrystallization. [ABSTRACT FROM AUTHOR]

A measurement of within-particle molecular transport is carried out using confocal Raman microscopy to probe the time-dependent accumulation of pyrene from an aqueous mobile phase into the center of individual C18-chromatographic particles.The linear dependence of the time-constant on particle radius indicates an adsorption barrier near the outer boundary of the particle. Monte Carlo simulations of within-particle pyrene diffusion, with the adsorption efficiency estimated from the planar-surface adsorption rate, predicts a diffusion-to-capture distance within the porous particle which is within 40 of that observed in the radial dependence of the pyrene within-particle accumulation results.

[sup.17]O solid-state NMR studies of waters of hydration in crystalline solids are presented. The [sup.17]O quadrupolar coupling and chemical shift (CS) tensors, and their relative orientations, are measured experimentally at room temperature for a-oxalic acid dihydrate, barium chlorate monohydrate, lithium sulfate monohydrate, potassium oxalate monohydrate, and sodium perchlorate monohydrate. The [sup.17]O quadrupolar coupling constants ([C.sub.Q]) 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 [C.sub.Q], 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' [sup.17]O spectral region for water coordinated to metals in solids. Key words: nuclear magnetic resonance, water, quadrupolar coupling, hydrogen bonding, chemical shifts, density functional theory, [sup.17]O solid-state NMR. Nous presentons les resultats d'etudes de RMN de l'[sup.17]O a l'etat solide portant sur les molecules d'eau d'hydratation dans des solides cristallins. Nous avons mesure experimentalement a temperature ambiante le couplage quadripolaire de l'[sup.17]O et les tenseurs de deplacement chimique (DC) ainsi que leurs orientations relatives de l'acide a-oxalique dihydrate, du chlorate de baryum monohydrate, du sulfate de lithium monohydrate, de l'oxalate de potassium monohydrate et du perchlorate de sodium monohydrate. Les constantes de couplage quadripolaires ([C.sub.Q]) de l'[sup.17]O varient de 6,6 a 7,35 MHz et les deplacements chimiques isotropes de -17 a 19,7 ppm. L'envergure du tenseur de DC de l'oxygene varie de 25 a 78 ppm. Ces resultats representent les premieres mesures completes de DC et de tenseur de gradient de champ electrique effectuees sur des molecules d'eau coordonnees a des metaux en phase solide. Nous avons observe que les calculs de la theorie de la fonctionnelle de la densite par la methode<>surestiment les valeurs de [C.sub.Q], probablement a cause de la dynamique de libration des molecules d'eau. Les valeurs calculees des tenseurs de DC correspondent aux valeurs experimentales seulement sur le plan qualitatif. L'absence de fortes correlations entre les donnees experimentales et calculees, et entre ces donnees et toute caracteristique structurale, s'explique par le mouvement des molecules d'eau et la variation globale relativement faible des parametres de RMN par rapport a la precision de mesure de ceux-ci. Quoi qu'il en soit, le deplacement chimique isotrope, la constante de couplage quadripolaire et l'envergure des tenseurs de DC permettent de distinguer clairement les echantillons etudies les uns des autres et d'etablir une <> dans la region spectrale de l'[sup.17]O correspondant aux molecules d'eau coordonnees aux metaux dans les solides. [Traduit par la Redaction] Mots-cles: resonance magnetique nucleaire, eau, couplage quadripolaire, liaison hydrogene, deplacements chimiques, theorie de la fonctionnelle de la densite, [sup.17]O RMN a l'etat solide., Introduction Water is essential to life, innumerable biochemical and inorganic processes, chemical reactions, and the structure and properties of various materials. (1,2) Water molecules play key structural roles in organic, [...]

A thorough investigation of solid-state NMR signal enhancement schemes and high-resolution techniques for application to the spin-7/2 [sup.43]Ca 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 [left and right arrow] -1/2), are carried out on four well-characterized [sup.43]Ca isotopically enriched calcium salts: Ca[(N[O.sub.3]).sub.2], Ca[(OD).sub.2], CaS[O.sub.4] x 2[H.sub.2]O, and Ca[(OAc).sub.2] x [H.sub.2]O. These results, in conjunction with numerical simulations of [sup.43]Ca 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 [sup.43]Ca quadrupolar coupling constant, which is the most significant source of resonance broadening in [sup.43]Ca NMR spectra. These samples are further investigated using [sup.43]Ca 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).sub.2] x 0.5[H.sub.2]O, 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 [sup.43]Ca solid-state NMR data for unknown and more complex materials with a higher degree of both sensitivity and resolution. Key words: [sup.43]Ca solid-state NMR spectroscopy, double-rotation NMR, signal enhancement, high-resolution quadrupolar NMR, calcium acetate hemihydrate, crystallography. Nous presentons un examen approfondi des schemas d'amplification du signal RMN a l'etat solide et des techniques de RMN du solide en haute resolution en vue de les appliquer au nucleide [sup.43]Ca, de spin 7/2. Quatre sels de calcium enrichis en isotope [sup.43]Ca et bien caracterises, soit le Ca[(N[O.sub.3]).sub.2], le Ca[(OD).sub.2], le CaS[O.sub.4] x 2[H.sub.2]O et le Ca[(OAc).sub.2] x [H.sub.2]O, ont ete soumis a des experiences d'amplification du signal au moyen de balayages a double frequence, d'impulsions de forme secante hyperbolique et de transfert de population assiste par rotor, qui permettent de manipuler les transitions satellites des noyaux quadripolaires de spin demi-entier afin de polariser la transition centrale (m = +1/2 [left and right arrow] 1/2). Nous avons utilise ces resultats, combines aux simulations numeriques de spectres RMN du [sup.43]Ca en conditions de rotation a l'angle magique, pour determiner la technique produisant l'amplification de polarisation la plus uniforme (ou la plus quantitative) et les facteurs d'amplification du signal les plus importants, et ce, sans egard a la valeur de la constante de couplage quadripolaire du [sup.43]Ca, qui est la principale source d'elargissement du a la resonnance dans les spectres RMN du [sup.43]Ca. Nous avons soumis ces echantillons a des analyses plus poussees au moyen de la spectroscopie RMN a double rotation afin d'obtenir des spectres RMN isotropes (ou semblables a des spectres en solution) d'une resolution exceptionnelle. En outre, par spectroscopie RMN a double rotation, on distingue trois positions uniques des atomes de calcium de Facetate de calcium dans sa forme semi-hydratee (Ca[(OAc).sub.2] x 0.5[H.sub.2]O) (dont la structure est inconnue), tandis que la spectroscopie de correlation multiquanta en rotation a l'angle magique, qui est une technique plus courante que la precedente, mais qui requiert plus de temps, ne permet de distinguer clairement que deux positions des atomes de calcium. Les resultats presentes dans le present article sauront etre utiles a d'autres chercheurs en spectroscopie RMN qui tentent d'accumuler des donnees de RMN du [sup.43]Ca a l'etat solide a partir de materiaux inconnus ou plus complexes, et ce, avec une meilleure sensibilite et une meilleure resolution. [Traduit par la Redaction] Mots-cles: spectroscopie RMN du [sup.43]Ca a l'etat solide, RMN a double rotation, amplification du signal, RMN quadripolaire a haute resolution, acetate de calcium semi-hydrate, cristallographie., Introduction Due to the availability of superconducting magnets with large fields (e.g., ≥ 18.8 T), nuclear magnetic resonance (NMR) studies on nuclides whose observation was thought to be too impractical [...]

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]

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. Key words: NMR, solid-state NMR, materials, biomolecules, non-covalent interactions. Le present article decrit certains points saillants des travaux de recherche menes dans mon laboratoire de l'Universite d'Ottawa au cours de la periode de 2005 a 2014. Mes recherches portent sur les domaines generaux de la RMN biomoleculaire et du solide, etdes applications de lachimie quantique. La forme de cet article est analogue acelle de l'expose quej'aipresente dans le cadre du prix Keith Laidler 2014 de la Societe canadienne de chimie, lors du 97e congres canadien de chimie et exposition qui s'est tenu a Vancouver en juin 2014. Apres une breve introduction, je presenterai quelques-unes de nos recentes avancees les plus interessantes et les plus passionnantes, classees selon les six sujets suivants: 1. Recherche fondamentale en RMN du solide; 2. Caracterisation des materiaux par cristallographie et RMN; 3. Agents pharmaceutiques et polymorphisme; 4. Interactions non covalentes: liaisons halogenes; 5. RMN biomoleculaire; 6. Developpement de logiciels. [Traduit par la Redaction] Mots-cles: RMN, RMN du solide, materiaux, biomolecules, interactions non covalentes., Introduction Canada has a strong research tradition in the field of NMR spectroscopy, (1,2,3,4,5,6,7) and following my doctoral work with Rod Wasylishen at Dalhousie University and at the University of [...]

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]

Double-rotation (DOR) solid-state NMR spectroscopy is a high-resolution technique developed in the late 1980s. Although multiple-quantum magic-angle spinning (MQMAS) became the most widely used high-resolution method for half-integer spin quadrupoles after 1995, development and application of DOR NMR to a variety of chemical and materials science problems has endured. This Trend article recapitulates the development of DOR NMR, discusses various applications, and describes possible future directions. The main technical limitations specific to DOR NMR are simply related to the size of the double rotor system. The relatively large outer rotor (and thus coil) used for most applications over the past 35 years translates into relatively low rotor spinning frequencies, a low filling factor, and weak radiofrequency powers available for excitation and for proton decoupling. Ongoing developments in NMR instrumentation, including ever-shrinking MAS rotors and spherical NMR rotors, could solve many of these problems and may augur a renaissance for DOR NMR. [Display omitted] • Advances in double-rotation solid-state NMR spectroscopy are reviewed. • DOR NMR provides high-resolution spectra of quadrupolar nuclei in one dimension. • Limitations include a poor filling factor, low spinning rates, and low rf powers. • New developments in magic angle spinning technology could reinvigorate DOR NMR. [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 [sup.13]C and [sup.23]Na 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. [sup.23]Na magic-angle spinning (MAS), double-rotation (DOR), and multiple-quantum magic-angle spinning (MQJMAS) 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 [sup.23]Na NMR data. The utility of carrying out both DOR and MQJMAS NMR experiments to identify all crystallographically unique sites is demonstrated. [sup.13]C cross-polarization MAS NMR spectra also provide complementary information on the number of molecules in the asymmetric unit and the crystallinity of the sample. Key words: nuclear magnetic resonance, solid-state NMR, sodium-23, polymorphism, hydrates, pharmaceuticals, DFT, X-ray diffraction, carbon-13. Le valproate de sodium est un compose pharmaceutique ayant des applications dans le traitement de l'epilepsie, les troubles bipolaires ainsi que d'autres maladies. Le valproate de sodium peut aussi exister dans de nombreuses phases solides hydratees ainsi que diverses formes stabilisees par acide conjugue pour lesquelles il est difficile d'obtenir de l'information structurelle. Dans cet article nous presentons une etude de RMN a l'etat solide du [sup.13]Cet [sup.23]Na de plusieurs formes du valproate de sodium pour lesquelles seulement une structure cristalline est connue. Nous montrons que les spectres de RMN de rotation a l'angle magique (MAS), double-rotation (DOR) et de quantum multiples en rotation a l'angle magique (MQJMAS) du [sup.23]Na peuvent etre utilises pour determiner le nombre de molecules dans l'unite asymetrique et les polyedres de coordination du sodium, ainsi que pour identifier la presence de formes amorphes. Nos donnees de RMN du [sup.23]Na indiquent que deux des formes du valproate de sodium ayant precedemment ete identifiees sont en fait identiques ou tres semblables. L'utilite d'accomplir des experiences DOR ainsi que MQJMAS pour identifier les sites cristallographiquement differents est demontree. Les spectres MAS avec polarisation croisee du [sup.13]C fournissent aussi de l'information complementaire concernant le nombre de molecules dans l'unite asymetrique ainsi que la cristallinite de l'echantillon. Mots-cles : resonance magnetique nucleaire, RMN a l'etat solide, sodium-23, polymorphisme, hydrates, produits pharmaceutiques, DFT, diffractrometrie de rayons X, carbone-13., Introduction The sodium salt of 2-propylvaleric (valproic) acid (see Fig. 1)is used as an anticonvulsant in the treatment of epilepsy, (1,2) as a mood stabilizer in the treatment of bipolar [...]

Halogen bonding to phosphorus atoms remains uncommon, with relatively few examples reported in the literature. Here, the preparation and investigation of the cocrystal bis(dicyclohexylphenylphosphine)(1,6-diiodoperfluorohexane) by X-ray crystallography and solid-state multinuclear magnetic resonance spectroscopy is described. The crystal structure features two crystallographically unique C--I...P halogen bonds [dI...P = 3.090 (5) A, 3.264 (5) A ] and crystallographic disorder of one of the 1,6-diiodoperfluorohexane molecules. The first of these is the shortest and most linear I...P halogen bond reported to date. 13C, 19F, and 31P magic angle spinning solid-state NMR spectra are reported. A 31P chemical shift change of -7.0 p.p.m. in the cocrystal relative to pure dicyclohexylphenylphosphine, consistent with halogen bond formation, is noted. This work establishes iodoperfluoroalkanes as viable halogen bond donors when paired with phosphorus acceptors, and also shows that dicyclohexylphenylphosphine can act as a practical halogen bond acceptor. [ABSTRACT FROM AUTHOR]

Halogen bonding to phosphorus atoms remains uncommon, with relatively few examples reported in the literature. Here, the preparation and investigation of the cocrystal bis(dicyclohexylphenylphosphine)(1,6‐diiodoperfluorohexane) by X‐ray crystallography and solid‐state multinuclear magnetic resonance spectroscopy is described. The crystal structure features two crystallographically unique C—I…P halogen bonds [dI…P = 3.090 (5) Å, 3.264 (5) Å] and crystallographic disorder of one of the 1,6‐diiodoperfluorohexane molecules. The first of these is the shortest and most linear I…P halogen bond reported to date. 13C, 19F, and 31P magic angle spinning solid‐state NMR spectra are reported. A 31P chemical shift change of −7.0 p.p.m. in the cocrystal relative to pure dicyclohexylphenylphosphine, consistent with halogen bond formation, is noted. This work establishes iodoperfluoroalkanes as viable halogen bond donors when paired with phosphorus acceptors, and also shows that dicyclohexylphenylphosphine can act as a practical halogen bond acceptor.The halogen‐bonded cocrystal bis(dicyclohexylphenylphosphine)(1,6‐diiodoperfluorohexane) is prepared mechanochemically and investigated by X‐ray crystallography and solid‐state NMR spectroscopy, revealing the presence of a rare C—I…P halogen bond. [ABSTRACT FROM AUTHOR]

The article presents evidence that supported-lipid bilayers can be deposited by vesicle fusion onto the interior surfaces throughout the wide-pore network of chromatographic silica particles.The thickness of a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) film and headgroup spacing are consistent with a single bilayer of DMPC deposited onto the pore surfaces.The porous-silica-supported model membranes could share benefits that planar-supported lipid bilayers bring to biosensing applications, but in a material which overcomes the limited surface area of a planar support.

The results of a [sup.35/37]Cl 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 [sup.35/37]Cl 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, [C.sub.Q]([sup.35]Cl) = 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 [sup.35]Cl 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. Key words: solid-state NMR, octamethylcalix[4]pyrrole, quadrupolar coupling, chemical shift tensor, halogen NMR, solvates, ion binding, receptors. On rapporte les resultats d'une etude RMN a l'etat solide (RMN-ES) du [sup.35/37]Cl du complexe du chlorure de 1-butyl- 3-methylimidazolium avec le meso-octamethylcalix[4]pyrrole (1). On a analyse les formes des raies obtenues pour des echantillons de poudre a l'etat stationnaire et a l'angle de rotation magique, a 9,4 et 21,1 T, pour en extraire le tenseur quadripolaire et le tenseur du deplacement chimique (DC) du [sup.35/37]Cl ainsi que leur orientation relative. La symetrie relativement elevee de l' environnement de coordination de l' ion chlorure se manifeste par la faible valeur de la constante de couplage quadripolaire, [C.sub.Q]([sup.35]Cl) = 1,0 MHz. Le deplacement chimique isotrope de 120 ppm (par rapport au NaCl) se trouve a la limite superieure de la plage typique observee pour les chlorhydrates organiques. Une consideration de l'anisotropie du deplacement chimique (portee, Ω = 50 ppm) et de la non coincidence des tenseurs quadripolaires et du deplacement chimique sont essentiels pour simuler correctement les spectres experimentaux. L'utilite des calculs des tenseurs quadripolaires et du deplacement chimique du chlore, par la theorie de la fonctionnelle de la densite en utilisant une onde amelioree par un operateur de projection et comportant une jauge (<< GIPAW-DFT >>), est verifie en comparant avec les donnees experimentales disponibles pour des chlorhydrates solides d'acides amines. Il est demontre que les calculs surevaluent systematiquement la valeur de la constante de couplage quadripolaire du [sup.35]Cl. Des calculs supplementaires sur divers modeles hydrates et solvates du compose 1 sont en accord avec une structure dans laquelle le solvant et l'eau d'hydratation sont absents. Mots-cles : RMN a l'etat solide, octamethylcalix[4]pyrrole, couplage quadripolaire, tenseur du deplacement chimique, RMN des halogenes, produits solvates, fixation d'ion, recepteurs. [Traduit par la Redaction], Introduction Calix[n]arene rings are metacyclophanes made up of aromatic units bridged with methylene links. These units have a hydrophobic wide rim and a hydrophilic narrow rim that encompass a cavity, [...]

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 [sup.35/37]Cl and [sup.43]Ca solid-state nuclear magnetic resonance (SSNMR) study of Ca[Cl.sub.2]. The [sup.35]Cl 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 Ca[Cl.sub.2] x 2[H.sub.2]O. Chlorine-35 SSNMR spectra are also presented for Ca[Cl.sub.2] x 6[H.sub.2]O, and when taken in concert, the SSNMR observations for Ca[Cl.sub.2], Ca[Cl.sub.2] x 2[H.sub.2]O, and Ca[Cl.sub.2] x 6[H.sub.2]O 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 [δ.sub.iso] 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 Ca[Cl.sub.2] x 2[H.sub.2]O, and to explore the isostructural relationship between Ca[Cl.sub.2] and Ca[Br.sub.2]. Finally, the [sup.43]Ca CS tensor span is measured to be 31(5) ppm for anhydrous Ca[Cl.sub.2], which represents only the fifth CS tensor span measurement for calcium. Key words: solid-state NMR, chlorine, [sup.35]Cl, [sup.37]Cl, [sup.43]Ca, Ca[Cl.sub.2], polymorphism, hydrates, [C.sub.Q], chemical shift anisotropy (CSA), electric field gradient. Les halogenures des metaux du groupe 2 et les hydrates d'halogenures metalliques sont des systemes modeles qui permettent comprendre la relation entre le gradient du champ electrique (GCE) et les tenseurs du deplacement chimique (DC) au niveau du noyau d' halogene et la structure electronique et moleculaire locale. Dans ce travail, on presente les resultats d'une etude de resonance magnetique nucleaire a l'etat solide (RMN-ES) du [sup.35/37]Cl et [sup.43]Ca du Ca[Cl.sub.2]. Les valeurs de la constante de couplage quadripolaire nucleaire du [sup.35]Cl, 8,82(8) MHz, et le DC isotrope du chlore, 105(8) ppm [par rapport au NaCl(aq) dilue], sont differentes de celles rapportees pour ce compose ainsi que les valeurs rapportes pour le Ca[Cl.sub.2] x 2[H.sub.2]O. Les spectres RMN-ES du [sup.35]Cl sont aussi presentes pour le Ca[Cl.sub.2] x 6[H.sub.2]O et, lorsqu'on les compare, les observations relatives aux spectres RMN-ES du Ca[Cl.sub.2], du Ca[Cl.sub.2] x 2[H.sub.2]O et du Ca[Cl.sub.2] x 6[H.sub.2]O demontrent clairement la sensibilite du GCE du chlore et des tenseurs du DC sur la symetrie locale et aux changements dans l'etat d'hydratation. Par exemple, les valeurs de [δ.sub.iso] diminuent avec une augmentation de l'hydratation. On a fait appel a des calculs selon la theorie de la fonctionnelle de la densite en utilisant une onde amelioree par un operateur de projection comportant une jauge (<< GIPAWDFT >>) pour corroborer les observations faites par RMN-ES, pour eliminer la presence d'autres hydrates dans nos echantillons, pour affiner les positions des atomes d'hydrogene dans le Ca[Cl.sub.2] x 2[H.sub.2]O et pour explorer la relation isostructurale entre le Ca[Cl.sub.2] et Ca[Br.sub.2]. Enfin, on a etabli que la portee du tenseur de DC du [sup.43]Ca est de 31(5) ppm pour le Ca[Cl.sub.2] anhydre, ce qui represente seulement la cinquieme valeur mesuree pour l'anisotropie du tenseur du DC du calcium. Mots-cles: RMN a l'etat solide, chlore, [sup.35]Cl, [sup.37]Cl, [sup.43]Ca, Ca[Cl.sub.2], polymorphie, hydrates, [C.sub.Q], anisotropie du deplacement chimique (ADC), gradient du champ electrique. [Traduit par la Redaction], Introduction Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is an important tool that is used to characterize structure and dynamics within a range of chemical systems. Recent developments in SSNMR (1,2) [...]

Zeroth-order regular approximation (ZORA) density functional theory (DFT) calculations of one-bond X--[sup.19]F 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. Key words: nuclear magnetic resonance, J coupling, ZORA-DFT calculations, natural localized molecular orbitals. Des calculs de theorie de la fonctionnelle de la densite (DFT) de couplage spin-spin nucleaire indirect (J)X--[sup.19]F d'une liaison employant l'approximation reguliere d'ordre zero (ZORA) ont ete effectues sur une serie de composes du fluore couvrant plusieurs geometries de la theorie de la repulsion des paires electroniques de la couche de valence (RPECV) ayant une symetrie pour laquelle J n' est pas forcement axialement symetrique. Les calculs demontrent que les composants antisymetriques de J sont seulement du meme ordre de magnitude que les composants du tenseur de couplage J symetrique pour tres peu de geometries et que dans les situations de symetrie approximativement axiale le long de la liaison, J est axialement symetrique. En general, differentes especes ayant la meme geometrie ont des orientations de tenseur similaires, des anisotropies de J du meme ordre de grandeur, par rapport a la constante de couplage isotropique, ainsi que les memes mecanismes de couplage dominants. Les structures ont par la suite ete modifiees afin de determiner la dependance des composants principaux de J par rapport a la geometrie. Ces donnees sont ensuite reliees aux orbitales moleculaires en employant une approche d' orbitales moleculaires localisees naturelles (NLMO) pour investiguer les constantes de couplage isotropiques. Nos resultats pourraient etre utiles dans la caracterisation complete de tenseurs J pour des systemes ayant des symetries qui ne necessite pas que J soit axialement symetrique ou coincident avec le tenseur de couplage dipolaire. Mots-cles: resonance magnetique nucleaire, calculs ZORA-DFT, couplage J, orbitales moleculaires localisees naturelles. [Traduit par la Redaction], Introduction Solid-state nuclear magnetic resonance (SSNMR) spectroscopy has become one of the prime methods for the characterization of solid materials. A wealth of information can be extracted from NMR spectra [...]

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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 [sup.13]C 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. Key words: imines, synthesis, microporous polymers, postsynthetic modification. On a prepare un reseau organique microporeux tres reticule a l'aide de coupleurs imines par condensation du tetrakis( 4-aminophenyl)methane avec du terephtaldehyde. Des etudes d'adsorption de gaz indiquent que le materiau comporte une microporosite permanente alors que des experiences d'echange de molecule invitee demontrent que les petites molecules peuvent diffuser dans le reseau. On a realise des modifications postsynthetiques de ce reseau microporeux par un traitement avec du borane dans le THF qui a permis de reduire les groupes imines en amines correspondantes, tel que demontre par la spectroscopie infrarouge et la RMN du [sup.13]C a l'etat solide dans le mode de la rotation a l'angle magique avec polarisation croisee (RAM-PC). Le materiau qui en resulte presente une resistance accrue a l'hydrolyse acide par comparaison avec le precurseur imine et il conserve sa facilite a absorber des molecules invitees. Le reseau amine peut etre amene a d'autres modifications postsynthetiques. On a demontre, en particulier, la possibilite d'acyler ce reseau a l'aide d'anhydride acetique. Mots-cles: imines, synthese, polymeres microporeux, modification postsynthetique. [Traduit par la Redaction], Introduction Microporous solids are an important class of materials because their small pore sizes and high surface area make them potentially useful for chemical separation, catalysis, or gas storage. (1) [...]

NMR parameters such as indirect nuclear spin-spin coupling (J), nuclear magnetic shielding (s), 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 ([J.sup.anti]) holds the distinction of remaining the only nonzero part of these fundamental NMR interaction tensors which has never been observed experimentally. Accordingly, effects from [J.sup.anti] are usually ignored, but it is important to consider when this is valid. An experimental strategy for observing [J.sup.anti] 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, [J.sup.anti] 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 [J.sup.anti.] Furthermore, [J.sup.anti] will only have an observable effect on the NMR spectra when its magnitude is comparable with that of [J.sub.iso] and with the difference in chemical shifts (in Hz) between the two sites. Finally, the first experimental attempts to measure [J.sup.anti] are reported, and experimental proof that no elements of [J.sup.anti]([sup.119.Sn],[sup.119.Sn]) 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 [J.sub.anti] are also illustrated. Key words: J coupling, solid-state NMR spectroscopy, indirect nuclear spin-spin coupling, [sup.119.Sn] NMR, symmetry, NMR relaxation, antisymmetric tensor. Les interactions de RMN, tel le couplage spin-spin nucleaire indirect (J), le blindage magnetique nucleaire (s), le couplage dipolaire direct (D) et le gradient du champ electrique (V) peuvent etre decrits correctement par des tenseurs de deuxieme rang. Chacune peut etre decomposee en composants isotropes, symetriques et antisymetriques; le nombre de ces trois composants qui peut etre differente de zero est un attribut caracteristique de chaque tenseur d'interaction. La portion antisyme trique de rang 1 de J ([J.sup.anti]) se distingue par le fait qu'il s'agit de la seule partie de ces tenseurs fondamentaux d'interaction RMN dont la valeur est differente de zero qui n'a pas encore ete observee experimentalement. Il en decoule qu'on ignore generalement les effets attribuables a [J.sup.anti], mais il est important de considerer quand cela est valide. On decrit une strategie experimentale basee sur les idees proposees originalement par Andrew et Farnell (Mol. Phys. 1968, 15, 157) pour observer [J.sup.anti] dans des echantillons en poudre de paires de spin homonucleaires fortement couples. La theorie de Andrew et Farnell a ete etendue aux echantillons en poudre et on presente des methodes qui permettent d'analyser les spectres RMN des echantillons en poudre. On a trouve que dans certains rares cas, le couplage [J.sup.anti] a le pouvoir d'affecter les formes des raies RMN des systemes de spin AB, mais que meme avec ces systemes, les caracteristiques les plus intenses des spectres ne sont pas affectees et elles peuvent etre analysees independamment de [J.sup.anti]. De plus, [J.sup.anti] n'aura un effet observable sur les spectres RMN que lorsque son amplitude sera comparable a celle de [J.sub.iso] et a la difference dans les deplacements chimiques (en Hz) entre les deux sites. Finalement, on rapporte les premiers efforts experimentaux a mesurer [J.sup.anti], et on demontre experimentallement qu'il n'y a pas d'elements de [J.sup.anti]([sup.119.Sn], [sup.119.Sn]) plus grand que 2900 Hz dans l'hexa(p-tolyl)di-etain. On illustre aussi les benefices des sequences modernes d'impulsions RMN avec filtrage a double quantum pour isoler les effets de [J.sup.anti]. Mots-cles : couplage J, spectroscopie RMN a l'etat solide, couplage spin-spin nucleaire indirect, RMN du [sup.119.Sn], relaxation RMN, tenseur antisymmetrique. [Traduit par la Redaction], Introduction One of the most useful aspects of NMR spectroscopy for relating spectroscopic observables to molecular structure and dynamics is the inherent orientation dependence of the fundamental NMR interactions. (1) [...]

The accurate calculation of the isotropic ([J.sub.iso]) 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 [J.sub.iso] 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 [J.sub.iso] 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. Key words: density functional theory, relativistic effects, spin-spin coupling constant, dipolar coupling, rovibrational averaging, alkali metal halides, group-17 fluorides, xenon fluorides. Le calcul precis des parties isotropes ([J.sub.iso]) et anisotropes (ΔJ) des tenseurs de couplage spin-spin nucleaire indirect est un test rigoureux pour la chimie quantique, en particulier pour les couplages impliquant des isotopes lourds pour lesquels on peut s'attendre a ce qu'il y ait un role important de jouer par les effets relativistes et les effets dus aux termes croises de la relativite et la correlation electronique. Des mesures experimentales sur des molecules diatomiques, en phase gazeuse, fournissent les donnees ideales pour verifier les resultats des approches theoriques puisque les donnees ne comportent pratiquement aucun effet intermoleculaire et que dans les cas favorables il est possible d'en extraire des anisotropies de couplage fiables. Sur la base des parametres de tenseur de couplage obtenus a partir d'une experience faisceau moleculaire pour des halogenures diatomiques de metaux alcalins, on a prepare un tableau des valeurs connues de [J.sub.iso] et, prenant en compte les corrections rotationnelles-vibrationnelles pour la constante de couplage dipolaire directe, on a determine des valeurs precises de ΔJ pour l'etat vibrationel fondamental. On a aussi effectue des calculs a base de principes premiers des tenseurs de couplage en faisant appel a un programme developpe recemment et base sur une theorie hybride de la fonctionnelle de la densite utilisant une approximation reguliere d'ordre zero relativiste a deux composantes << ZORA >>. Les valeurs experimentales de [J.sub.iso] et de ΔJ sont ainsi reproduites avec des coefficients de correlation respectifs de 0,993 et 0,977. On discute des tendances periodiques des constantes de couplage et de leur correlation avec le produit des numeros atomiques de noyaux participants au couplage. Enfin, la methode fonctionnelle hybride a aussi ete testee avec succes avec des donnees experimentales pour une serie de fluorures de xenon polyatomiques et un groupe de fluorures du groupe 17. Mots-cles : theorie de la fonctionnelle de la densite, effets relativistes, constante de couplage spin-spin, couplage dipolaire, moyenne rovibrationnelle, halogenures de metaux alcalins, fluorures du groupe 17, fluorures de xenon. [Traduit par la Redaction], Introduction Indirect nuclear spin-spin coupling (J-coupling) tensors are widely used, in the form of their isotropic average ([J.sub.iso]), for structural elucidation in diverse areas of the chemical, (3-7) materials, (8,9) [...]

The interaction of cytochrome c with cardiolipin-containing phospholipid vesicles, serving as models of the outer mitochondrial membrane (OMM), is investigated to probe cytochrome c-induced permeability. Structural changes observed in the Raman spectra during permeabilization indicate acyl chain disordering along with decreased intensity of the cardiolipin cis-double-bond stretching modes. The results suggest that cytochrome-induced permeabilization proceeds through selective interaction of cytochrome c with cardiolipin, resulting in protein unfolding, where the unfolded form interacts with cardiolipin acyl chains within the bilayer to induce permeability.

Abstract: 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 [...]

Three basic strategies for market entry are establishing niches, reconfiguring value chains, and leveraging existing assets. Key combinations of these strategies are described.

Solid-state chlorine-35/37 NMR for L-tryptophan hydrochloride and DL-arginine hydrochloride monohydrate have helped in understanding the trends in the spans of the chlorine chemical shift tensors in amino acid hydrochlorides. The inference indicates the application of chlorine NMR interaction tensors in the refinement of proton positions in structurally similar compounds like chlorine ion channels, for which neutron diffraction data is not available.

A 23Na solid-state NMR (SSNMR) study of two sodium lariat ether complexes, in which a sodium cation interacts with an indolyl group that models the side chain of tryptophan is described. It is seen that the observed shielded isotropic chemical shifts are associated with the presence of cation-[pi] interaction.