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A brief description of some of the key individuals at McGill University and their contributions to the development of crystallography is given. This is followed by examples of recent structure determinations, which include organic heterocycles, natural products, inorganic salts, and organometallic complexes. Specifically, the bispyridinium adduct of protoporphyrin, the piperidinyl adduct of 3,7-dichloroquinine, trisbenzylmethylthiol, sodium methylarsonium (V), potassium hydroxylamine sulfonate, Vaska's complex adduct from the oxidative addition of p-tolylmercaptan, and a bis isocyanoiminotriphenylphosphorane adduct of rutheniumdichloridetristriphenylphosphine are described. Key words: X-ray crystallography, protoporphyrin, methylarsonium, hydroxyaminesulfonate, organometallic. Cet article presente brievement certains chercheurs renommes de l'Universite McGill et decrit leur apport au developpement de la cristallographie. Cette mise en contexte est suivie d'exemples recents d'elucidation de structures, dont des heterocycles organiques, des produits naturels, des sels inorganiques et des complexes organometalliques. En particulier, nous decrivons l'adduit bispyridinium de la protoporphyrine, l'adduit piperidinyle de la 3,7 dichloroquinine, le tribenzylmethanethiol, le methylarseniate(V) de sodium, l'hydroxylaminesulfonate de potassium, l'adduit provenant de l'addition oxydante du p tolylmercaptan au complexe de Vaska et un adduit bis(isocyanoiminotriphenylphosphorane) du dichlorotris(triphenylphosphine)ruthenium. Mots-cles: diffraction des rayons X, protoporphyrine, methylarsenate, hydroxylaminesulfonate, organometallique., Introduction Structural chemistry is a mainstay of our science, and its importance is demonstrated by the exponential growth in the numbers of crystal structure determinations, the continual development of new [...]

Mussel byssus is an important model for bio-inspired design, due to the discovery that byssus proteins enriched in the non-canonical amino acid 3,4-dihydroxyphenylalanine (DOPA) form dynamic, load-bearing metal coordination cross-links. While it was initially assumed that cross-linking was based on DOPA–Fe coordination, recent findings challenge this assumption, suggesting that mussels preferentially utilize vanadium. Yet, the details are still unclear. Here, we performed a cross-disciplinary investigation of vanadium use by mussels for formation and function of the byssus, harnessing Raman and X-ray absorption spectroscopy, DFT modeling, and rheological studies. Our results indicate that Mytilus mussels actively uptake vanadium for the express purpose of incorporating it into the byssus, and that byssus V content is influenced by local seawater vanadium concentration. The vanadium oxidation state in the byssus appears to be a mixture of V(IV) and V(III), while the dominant coordination geometry is octahedral tris–DOPA–V. Rheological studies on model DOPA-enriched polymer hydrogels demonstrated that vanadium-reinforced gels exhibit more solid-like behavior than iron-reinforced gels at seawater pH, which may explain why mussels prefer vanadium for building their byssus. These findings offer new insights for how vanadium is used in biology, but also offer further inspiration for novel mussel-inspired adhesive, coatings, and supramolecular materials. [ABSTRACT FROM AUTHOR]

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Background: Epidemiologic studies indicate that early life arsenic exposures are linked to an increased risk of cardiovascular diseases. Different oxidation and methylation states of arsenic exist in the environment and are formed in vivo via the action of arsenic (+3 oxidation state) methyltransferase (As3MT). Methylated arsenicals are pro-atherogenic postnatally, but pre- and perinatal effects are unclear. This is particularly important because methylated arsenicals are known to cross the placenta. Objectives: We tested the effects of early life exposure to inorganic and methylated arsenicals on atherosclerotic plaque formation and its composition in apolipoprotein E knock-out ([apoE.sup.-/-]) mice and evaluated whether [apoE.sup.-/-] mice lacking As3MT expression were susceptible to this effect. Methods: We exposed [apoE.sup.-/-] or [apoE.sup.-/-] /[As3MT.sup.-/-] mice to 200 ppb inorganic or methylated arsenic in the drinking water from conception to weaning and assessed atherosclerotic plaques in the offspring at 18 wk of age. Mixed regression models were used to estimate the mean difference in each outcome relative to controls, adjusting for sex and including a random effects term to account for within-litter clustering. Results: Early life exposure to inorganic arsenic, and more profoundly methylated arsenicals, resulted in significantly larger plaques in the aortic arch and sinus in both sexes. Lipid levels in these plaques were higher without a substantial difference in macrophage numbers. Smooth muscle cell content was not altered, but collagen content was lower. Importantly, there were sex-specific differences in these observations, where males had higher lipids and lower collagen in the plaque, but females did not. In mice lacking As3MT, arsenic did not alter the plaque size, although the size was highly variable. In addition, control [apoE.sup.-/-] /[As3MT.sup.-/-] mice had significantly larger plaque size compared with control [apoE.sup.-/-]. Conclusion: This study shows that early life exposure to inorganic and methylated arsenicals is pro-atherogenic with sex-specific differences in plaque composition and a potential role for As3MT in mice. https://doi.org/10.1289/EHP8171, Introduction Arsenic is a toxicant naturally found in soil, water, and air. (Mandal and Suzuki 2002; Nordstrom 2002). The World Health Organization (WHO) has set a maximum contaminant level of [...]

1-(2-Nitrophenyl)-1-phenylamine and methyl 4-((2-nitrophenyl)amino)benzoate have been transformed into their corresponding urea derivatives through the action of chlorosulfonyl isocyanate. The initial sulfimidate product from the former reaction has sufficient stability so that it can be isolated and characterized as its disodium salt, and this, as well as three other subsequent products, have been characterized by X-ray diffraction. The corresponding intermediary urea was converted into its hydrazine derivative via a Hofmann rearrangement under oxidative conditions. Density functional theory has been used to examine the nature of the intermediates and transition states for the Hofmann rearrangement. There is little theoretical indication for a cyclic aziridinonium intermediate and the transition state between the urea and the isocyanate corresponds to a reactant-like rotation of the planar singlet nitrene before migration and formation of the new N-N bond. Key words: hydrazines, Hofmann rearrangement, sulfimate salt. La 1-(2-nitrophenyle)-1-phenylamine et la 4-((2-nitrophenyle)amino)benzoate de methyle ont ete transforme par leur reaction avec l'isocyanate de chlorosulfonyle en leurs urees correspondantes. Dans le premier cas, le produit initial de cette reaction, un sulfimide, demontre une stabilite qui permet son isolement comme sel de sodium. Celui-ci ainsi que trois produits ulterieurs ont ete caracterises par diffraction de rayons X. L'uree de 1-(2-nitrophenyle)-1-phenylamine a ete transforme en hydrazine par rearrangement de Hofmann sous conditions oxydatives. La theorie de la fonctionnelle de la densite a ete utilise afin d'examiner les intermediates et les etats de transition de ce rearrangement. Les calculs indiquent qu'un intermediate aziridononium cyclique est peu probable et que l'etat de transition qui mene de l'uree a l'isocyanate et finalement a l'hydrazine correspond a une rotation de la nitrene planaire de forme singulet avant sa migration et la formation d'une nouvelle liaison entre les deux atomes d'azote. Mots-cles: hydrazines, Hofmann rearrangement, sel sulfimate., Introduction Although 1,1-diarylhydrazines have proven useful in medicinal chemistry (1) and in the catalysis of hydrohydrazination reactions, (2, 3) their syntheses (4) often require a two-step nitrosation/reduction of a diaryl [...]

Sulfur K-edge X-ray absorption spectroscopy (S K-edge XAS) was applied to investigate the electronic structure of primary and tertiary S-nitrosothiols. Our experimental data, supported by density functional calculations, indicate that changes at Ca affect the S-nitroso group through both inductive and direct orbital effects. Furthermore, our data are consistent with a weakening of the S-N bond in tertiary S-nitrosothiols as compared to their primary S-nitroso analogues. These results support existing computational models and suggest that the reactivity of S-nitrosothiols is not dominated by the electronics of the S-N bond. Key words: S-nitrosothiols, X-ray absorption spectroscopy (XAS), S-nitroso-N-acetylpenicillamine (SNAP), nitrosoglutathione. On a fait appel a la spectroscopie d'absorption des rayons-X pres du seuil K du soufre (SAX pres du seuil K du soufre) pour etudier la structure electronique de S-nitrothiols primaires et tertiaires. Les donnees experimentales et les calculs de la fonctionnelle de la densite indiquent que les changements au niveau du Ca affectent le groupe S-nitroso par des effets inductifs ainsi que par des effets directs d'orbitales. De plus, les donnees sont en accord avec un affaiblissement de la liaison S-N dans les S-nitrosothiols primaires par rapport a leurs analogues S-nitroso primaires. Ces resultats supportent les modeles existants derives de calculs theoriques et ils suggerent que la reactivite des S-nitrosothiols n'est pas dominee par les effets electroniques de la liaison S-N. Mots-cles: S-nitrosothiols, spectroscopie d'absorption des rayons X (SAX), S-nitroso-N-acetylpenicillamine (SNAP), nitrosoglutathion. [Traduit par la Redaction], Introduction S-Nitrosothiols are important nitric oxide (NO) derivatives with potential therapeutic applications. (1) Nitric oxide has been implicated in various physiological processes, including neurotransmission, (2) induction of smooth muscle relaxation, [...]

Three β-galactosidase-specific nitric-oxide-releasing diazeniumdiolate conjugated probes were prepared as a prelude to studies of new potential molecular MRI imaging agents. A glycosylated derivative, 2e, designed to be trafficked across cell membranes, was also prepared. We report, in detail, the synthesis and characterization of these probes. In addition, the release of diazeniumdiolate from the probes by β-galactosidase-catalyzed hydrolysis was used to estimate their efficacy as serum-stable, specific NO donors. Key words: nitric oxide, diazeniumdiolate, glycosylated, galactosidase. Comme prelude a des etudes de nouveaux produits pouvant eeventuellement etre utilises comme agents moleculaires en imagerie de resonance magnetique (IRM), on a prepare; trois nouvelles sondes speecifiques pour les β-galactosidase et conjuguees a un diazeniumdiolate qui libere de l'oxyde nitrique. On a aussi prepare un derive glycosyle, 2e, qui devrait pouvoir penetrer a l'interieur des membranes des cellules. On rapporte, en detail, la synthese et la caracterisation de ces sondes. De plus, on utilise le fait que l'hydrolyse catalyseee par le β-galoactosidase libere le diazeniumdiolate des sondes pour evaluer leur efficacite comme donneurs speecifiques de NO, stables dans le serum. Mots-cles: oxyde nitrique, diazeniumdiolate, glycosyle, galactosidase., Introduction With the numerous biological roles of nitric oxide (NO), there is now great interest in developing NO-releasing compounds capable of providing required quantities of NO to specific biological tissues [...]

Background: Arsenic is metabolized through a series of oxidative methylation reactions by arsenic (3) methyltransferase (As3MT) to yield methylated intermediates. Although arsenic exposure is known to increase the risk of atherosclerosis, the contribution of arsenic methylation and As3MT remains undefined. Objectives: Our objective was to define whether methylated arsenic intermediates were proatherogenic and whether arsenic biotransformation by As3MT was required for arsenic-enhanced atherosclerosis. Methods: We utilized the [apoE.sup.-/-] mouse model to compare atherosclerotic plaque size and composition after inorganic arsenic, methylated arsenical, or arsenobetaine exposure in drinking water. We also generated [apoE.sup.-/-] /[As3mt.sup.-/-] double knockout mice to test whether As3MT-mediated biotransformation was required for the proatherogenic effects of inorganic arsenite. Furthermore, As3MT expression and function were assessed in in vitro cultures of plaque-resident cells. Finally, bone marrow transplantation studies were performed to define the contribution of As3MT-mediated methylation in different cell types to the development of atherosclerosis after inorganic arsenic exposure. Results: We found that methylated arsenicals, but not arsenobetaine, are proatherogenic and that As3MT is required for arsenic to induce reactive oxygen species and promote atherosclerosis. Importantly, As3MT was expressed and functional in multiple plaque-resident cell types, and transplant studies indicated that As3MT is required in extrahepatic tissues to promote atherosclerosis. Conclusion: Taken together, our findings indicate that As3MT acts to promote cardiovascular toxicity of arsenic and suggest that human AS3MT SNPs that correlate with enzyme function could predict those most at risk to develop atherosclerosis among the millions that are exposed to arsenic. https://doi.org/10.1289/EHP806, Introduction Arsenic exposure in humans is recognized as a major public health issue [Agency for Toxic Substances and Disease Registry (ATSDR) 2013; World Health Organization (WHO) 2001), where tens of [...]

The article illustrates the methylation of the remarkable new sydnone N-oxide derivatives, which normally occurs either at the disubstituted ring nitrogen or the oxygen of the N-oxide. The kinetic and the thermodynamic control in the alkylation site of an electron-rich heterocycle, which leads to such an N-alkylation for a diazenium diolate, are also explained.

Abstract: Traube's dianion, 4-methylcarboxysydnone-3-hydroxylate (2), and its monomethyl ester (1) are readily isolated as their di- and mono-potassium salts from the reaction of nitric oxide with dimethylmalonate and potassium methoxide [...]

Study is conducted to examine O(super 2)-methyl-1-(N,N-dimethylamino)diazen-1-ium-1,2-diolate [Me(sub 2)NN(O)=NOMe], a simple nitrogen-bound diazeniumdiolate to obtain evidence of the presence of elusive trans isomer or ascertain upper limit of low concentration. An analysis suggests that, down to a detection limit of about 1/1000, only a small amount of trans(E) diazeniumdiolate, < 0.05% is present at room temperature.

The isomers of thiazate ([NSO.sup.-]) have a rich chemistry that is examined theoretically and experimentally for their thermal and coordination characteristics. The intramolecular isomerization of [NSO.sup.-] to monothionitrite ([ONS.sup.-]) is predicted (B3LYP/6-311+G*) to have a substantial barrier, greater than 418 kJ [mol.sup.-1]. Thus, thiazates are expected to be relatively thermally stable towards isomerization, and DSC indicates that KNSO undergoes a two stage irreversible thermolytic decomposition only beginning at 132 °C with ΔH = -116.3 kJ [mol.sup.-]. As a ligand, the thiazate can adopt a range of geometries in response to the metal's oxidation state and ligand sphere. For example, in Ru(TTP)(NO)(NSO) the ligand has a markedly bent Ru-N-S geometry, and when contrasted with other structurally characterized thiazate coordination compounds, it is concluded that in addition to σ donation the thiazate binds to metals in an amphoteric manner because of either a forward or reverse OSN → M π donation similar to transition metal nitrosyl, amido, and imido complexes. Key words: thiazate, isomerization, thermolysis, amphoteric ligand, coordination chemistry. Les isomeres du thiazate ([NSO.sup.-]) offrent une chimie riche qu'on a examinee d'un point de vue experimental et theorique dans le but de determiner leurs caracteristiques thermiques et de coordination. Selon des calculs theoriques (B3LYP/6-311+G*) l'isomerisation intramoleculaire du [NSO.sup.-] en monothionitrite ([ONS.sup.-]) doit presenter une barriere importante, superieure a 418 kJ [mo1.sup.-1]. On s'attend doric a ce que les thiazates soient thermiquement relativement stables vis-a-vis l'isomerisation et la calorimetrie a balayage differentiel indique que le KNSO subit une decomposition thermolytique irreversible en deux etapes qui ne commence qu'a 132 °C, avec un ΔH = 116,3 kJ [mol.sup.-1]. Comme ligand, le thiazate peut adopter une grande variete de geometries en reponse a l'etat d'oxydation du metal et a la sphere du ligand. Par exemple, dans le Ru(TTP)(NO)(NSO), le ligand adopte une geometrie Ru-N-S tres tendue et, quand on le met en opposition a d'autres composes de coordination du thiazate dont la structure a ete caracterisee, on en conclut que, en plus d'une donation σ, le thiazate se lie aux metaux d'une facon amphotere qui est due une donation π OSN → M (ou l'inverse) semblable celle des complexes nitrosyles, amido et imido des metaux de transition. Mots cles : thiazate, isomerisation, thermolyse, ligand amphotere, chimie de coordination. [Traduit par la Redaction], The remarkably complex family of thiazyl anions, collectively described by the formula [[[N.sub.x][S.sub.y][O.sub.z]].sup.-n], include two comparatively simple isomeric species with x = y = z = 1, the thiazate anion [...]

Monomethylation of the potentially ambident RNH[N(O)NO](super -) ion (R=isoprophyl or cyclohexyl) is shown to occur at the terminal oxygen to yield the novel diazeniumdiolate structural unit, RNHN-(O)=NOMe. The evidence for extensive delocalization and associated changes in bond order on ionizing RNHN(O)-NOR' are found in density functional theory calculation using Gaussian 03 with B2LYP/6-311++G** basis sets.

[beta]-Hematin, the crystalline heme detoxification product of red blood cell digestion by the malaria, parasite, can reversibly absorb up to 14% of its mass in water. Heating hydrated [beta]-hematin to temperatures greater than 150 [degrees]C results in loss of the hydrated water, which is readily reabsorbed on standing in air at room temperature. The amount of water absorbed is source dependent with highly crystalline samples produced by the anhydrous-base-mediated dehydrohalogenation being twice as absorptive as more amorphous samples produced by the aqueous acid precipitation method. Infrared spectroscopy and thermal gravimetric analysis have been used to measure the amount of water lost and gained during these experiments. X-ray powder diffraction has been used to characterize the effect of hydration state on the lattice parameters. Taken together these experiments resolve literature discrepancies concerning the elemental composition of synthetic and extracted natural [beta]-hematin. Key words: malaria pigment, hemozoin, [beta]-hematin, hydration, thermal gravimetric analysis, powder diffraction.

Results show that conformational changes in the antimicrobial peptide pediocin AcH, upon membrane vesicle binding, lead to a betaalpha domain structure. Data indicate that secondary structure of pediocin in detergents is comparable to that observed in vesicles, suggesting the role of hydrocarbon-water interface in pediocin AcH structure.

The density functional calculations (B3YLP/6-311++G(super **) are used to evaluate the bonding, ground-state structures and energy landscape for the different conformers of methanetris(diazene-N-oxide-N'-hydroxylate)(super 3-) trianion, a new type of a molecular propeller, and its corresponding triprotonated acid. Theoretically, it was found to be most consistent with a correlated or geared rotation of the different blades.

Research has been conducted on the metal-substituted forms of 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase. The metal binding properties of the series of these forms have been investigated via UV-vis and EPR spectroscopy.

The synthesis of four double-chain surfactant cobalt(III)complex pairs is described. Results show that the compounds are mostly insoluble in water and their use as surfactants is very limited. However, the ratio of diastereomer increases from ethanol-water to water due to hydrophobic effect of N-alkylethylenediamine ligand aggregation in water.