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The synthesis and characterisation (IR, NMR, HR-MS, and X-ray crystallography) of six oxazoline Zn complexes, containing enolate ligands derived from a series of (Z)-1-R-2-(4',4'-dimethyl-2'-oxazolin-2'-yl)-efh-1-en-1-ols (R=[C.sub.6][H.sub.5], [C.sub.6][H.sub.4]-p-N[O.sub.2], [C.sub.6][H.sub.4]-p-O[CH.sub.3], [CF.sub.3], [CH.sub.3], or [CMe.sub.3]) is detailed. All derivatives are air-stable solids of formula Zn[([L.sup.n]).sub.2] and are formed in the presence of the title ligands and [NEt.sub.3]. Reasonable yields (53%-82%) are obtained with the exception of R= [CMe.sub.3] (9%); in this case, by-product formation and high solubility affected complex isolation. Crystallographic characterisation reveals that in all cases the ligands are bound in a [kappa].sup.2]-N, O-bonding motif. Little structural diversity is noted within the series; these complexes are further placed into structural context with related Zn materials containing oxazoline, phenolate, and (or) Schiff base ligands. Key words: oxazoline, coordination complexes, zinc, enolate, X-ray crystal structure, Introduction The naturally occurring Group 12 elements hold a unique position within coordination chemistry due to the overwhelming predominance of the +2 oxidation state. This is, of course, a result [...]

The photophysical properties of four 1,3,6-trisubstituted pyrazolo[3,4-d][1,2,3]triazoles were studied by a combination of UV--vis and fluorescence spectroscopy as well as density functional theory (DFT) and time-dependent DFT calculations. All four compounds are weakly fluorescent. Upon protonation with trifluoroacetic acid, all compounds display a drastic luminescence turn-on. The addition of excess trifluoroacetic acid further enhances the luminescence intensity, which is tentatively attributed to the formation of extended hydrogen bonding network rather than the formation of doubly protonated 1,3,6-trisubstituted pyrazolo[3,4-d][1,2,3]triazoles. All new compounds were characterized by nuclear magnetic resonance and X-ray crystallography. Key words: luminescence, UV--vis spectroscopy, pyrazole, triazole, fused N-heterocycles, Introduction Nitrogen-rich fused heterocycles are an important class of compounds with wide applications in the rapidly expanding fields of medicinal chemistry, drug discovery, and functional material development. (1-8) Pyrazolo[3,4-d][1,2,3]triazoles are [...]

A poly(vinylpyrrolidone) end-functionalized with a carboxylic acid group (PVP-[CO.sub.2]H) was synthesized by reversible addition-fragmentation chain transfer (RAFT)/macromolecular design via the interchange of xanthates (MADIX) polymerization mediated by 4-(O-ethylxanthyl)methyl benzoic acid. The molecular weight of the as-synthesized PVP-[CO.sub.2]H was estimated through UV-vis spectroscopy ([M.sub.n(UV-vis)] = 7322 g/mol), gel permeation chromatography (GPC) ([M.sub.n(GPC)] = 8670 g/mol), and [.sup.1]H NMR, ([M.sub.n(NMR)] = 8207 g/mol). The values obtained were close with the theoretical molecular weight ([M.sub.n(th)] = 7925 g/mol). Subsequently, the preformed PVP-[CO.sub.2]H was activated to produce N-succinimidyl poly(vinylpyrrolidone) (PVP-NHS). This precursor was covalently coupled to papain to produce bioconjugate PVP-papain. The functional group modifications in the PVP chain-end were observed by the variations in the chemical shift values by [.sup.1]H and [.sup.13]C NMR and FTIR analysis at each step of the synthesis. The molecular weight of the PVP-papain was obtained by SEC-HPLC and suggests that, on average, four or five chains of PVP-[CO.sub.2]H were attached to one papain molecule. Compared with papain, the PVP-papain exhibited significantly improved catalytic activity, pH, and thermal stability. Additionally, the storage studies showed that the catalytic activity of PVP-papain was about 79% versus the native enzyme (29%), and this activity was maintained even when it was stored for 25 days. Key words: RAFT/MADIX N-vinylpyrrolidone, papain bioconjugation, enzymatic activity, NMR characterization. Nous avons synthetise une poly(vinylpyrrolidone) dont le groupe terminal est une fonction acide carboxylique (PVP-[CO.sub.2]H) par la technique RAFT (polymerisation radicalaire controlee par transfert de chaine reversible par addition-fragmentation)/MADIX (design macromoleculaire par echange de xanthates) facilitee par l'acide 4-(O-ethylxanthyl)methylbenzoique. Le poids moleculaire de la PVP-[CO.sub.2]H synthetisee telle quelle a ete estime par spectroscopie UV-vis ([M.sub.n(UV-vis)] = 7322 g/mol), chromatographie sur gel permeable (GPC) ([M.sub.n(GPC)] = 8670 g/mol) et RMN [.sup.1]H ([M.sub.n(RMN)] = 8207 g/mol). Les valeurs obtenues etaient proches du poids moleculaire theorique ([M.sub.n(th)] = 7925 g/mol). Par la suite, la PVP-[CO.sub.2]H prealablement formee a ete activee pour produire la N-succinimidylpoly(vinylpyrrolidone) (PVP-NHS). Nous avons ensuite fixe ce precurseur a la papaine par couplage covalent pour produire le bioconjugue PVP-papaine. Les variations des valeurs de deplacement chimique en RMN [.sup.1]H et [.sup.13]C et l'analyse des spectres FTIR ont permis de constater les modifications du groupe fonctionnel a l'extremite de chaine de la PVP a chaque etape de la synthese. Nous avons pu estimer le poids moleculaire du bioconjugue PVP-papaine par chromatographie d'exclusion sterique en phase liquide a haute performance (SEC-HPLC), et les resultats semblent indiquer que quatre ou cinq chaines de PVP-[CO.sub.2]H, en moyenne, sont fixees a une molecule de papaine. Comparativement a la papaine, le bioconjugue PVP-papaine a montre une amelioration significative de l'activite catalytique, de la stabilite au pH et de la stabilite thermique. Les etudes de conservation ont egalement revele que l'activite catalytique du bioconjugue PVP-papaine etait d'environ 79%, par rapport a celle de l'enzyme native, qui etait de 29%, et que cette activite etait maintenue meme lorsque le bioconjugue etait entrepose pendant 25 jours. [Traduit par la Redaction] Mots-cles : polymerisation RAFT/MADIX de la N-vinylpyrrolidone, bioconjugaison de la papaine, activite enzymatique, caracterisation par RMN., Introduction The chemical modification of enzymes through bioconjugation with biological or synthetic polymers is an excellent strategy for enhancement of enzymatic activity and stability, and in some cases, it can [...]

As one of mature enhanced oil recovery (EOR) technologies, polymer flooding has been extensively applied in oilfield. In this study, new hydrophobically associative copolymers were synthesized by free-radical polymerization of acrylamide (AM), acrylic acid (AA), vinyl-modified p-cyclodextrins, and a water-soluble hydrophobic macromonomer (AA-APE-20). Fourier transform infrared, protonnuclear magnetic resonance, and scanning electron microscopy verified the structure of hydrophobically associative polymers (HDAPAMs). Compared with partially hydrolyzed polyacrylamide (HPAM), multiple intermolecular forces including chelation between ethoxyl (EO) group and [Ca.sup.2+]/[Mg.sup.2+], electrostatic bridges between EO groups and carboxyl groups (--COO-), hydrogen bonding between EO groups and AM groups (--CO[NH.sub.2]), hydrophobic association among nonyl phenol groups, and host-guest inclusion interaction endowed HDAPAMs favorable temperature-resistance, salt-resistance, and displacement efficiency. It was found that HDAPAMs showed evident temperature-response, salt thickening effect, favorable thixotropy, and viscoelasticity. Compared with HPAM, the core flooding experiments demonstrated that HDAPAMs could further enhance 6.97% to 8.43% oil recovery, even after HPAM flooding used. All the results revealed the EOR potential in HDAPAMs flooding. KEYWORDS EOR, flow behavior, hydrophobically associative copolymers, multiple intermolecular forces, rheological properties, 1 | INTRODUCTION As one of enhanced oil recovery (EOR) techniques in oilfields, polymer flooding has been extensively used for several decades for its obvious effect on increasing oil production [...]

Background Cryptosporidium is an important gut microbe whose contributions towards infant and immunocompromise patient mortality rates are steadily increasing. Over the last decade, we have seen the development of various tools and methods for studying Cryptosporidium infection and its interactions with their hosts. One area that is sorely overlooked is the effect infection has on host metabolic processes. Results Using a .sup.1H nuclear magnetic resonance approach to metabolomics, we have explored the nature of the mouse gut metabolome as well as providing the first insight into the metabolome of an infected cell line. Statistical analysis and predictive modelling demonstrated new understandings of the effects of a Cryptosporidium infection, while verifying the presence of known metabolic changes. Of note is the potential contribution of host derived taurine to the diarrhoeal aspects of the disease previously attributed to a solely parasite-based alteration of the gut environment, in addition to other metabolites involved with host cell catabolism. Conclusion This approach will spearhead our understanding of the Cryptosporidium-host metabolic exchange and provide novel targets for tackling this deadly parasite. Keywords: Cryptosporidiosis, NMR, Metabolomics, COLO-680N, Taurine, Author(s): Christopher N. Miller[sup.1] , Charalampos G. Panagos[sup.2,5] , William R. T. Mosedale[sup.1] , Martin Kvác[sup.3,4] , Mark J. Howard[sup.2,6] and Anastasios D. Tsaousis[sup.1] Background Cryptosporidiosis is a disease characterised [...]

A central feature of quantum mechanics is that a measurement result is intrinsically probabilistic. Consequently, continuously monitoring a quantum system will randomly perturb its natural unitary evolution. The ability to control a quantum system in the presence of these fluctuations is of increasing importance in quantum information processing and finds application in fields ranging from nuclear magnetic resonance (1) to chemical synthesis (2). A detailed understanding of this stochastic evolution is essential for the development of optimized control methods. Here we reconstruct the individual quantum trajectories (3-5) of a superconducting circuit that evolves under the competing influences of continuous weak measurement and Rabi drive. By tracking individual trajectories that evolve between any chosen initial and final states, we can deduce the most probable path through quantum state space. These pre- and post-selected quantum trajectories also reveal the optimal detector signal in the form of a smooth, time-continuous function that connects the desired boundary conditions. Our investigation reveals the rich interplay between measurement dynamics, typically associated with wavefunction collapse, and unitary evolution of the quantum state as described by the Schrodinger equation. These results and the underlying theory (6), based on a principle of least action, reveal the optimal route from initial to final states, and may inform new quantum control methods for state steering and information processing., Our experiment focuses on the dynamics of two quantum levels of a superconducting circuit (a quantum bit, or qubit), which can be continuously measured and excited by microwave pulses. To [...]

Quantum chemical calculations are performed to study cooperativity and substituent effects between halogen bond and sodium bond interactions in NCX ... NCNa ... NCY complexes, where X = F, Cl, Br, I and Y = H, F, OH. These effects are studied in terms of equilibrium geometry, interaction energy, [sup.15]N nuclear magnetic resonance (NMR) parameters, and electron density analysis of the complexes at the MP2/aug-cc-pVTZ level. The X ... N and Na ... N bond lengths in the ternary systems are always shorter than those in the corresponding dyads. In each triad, the decrease in the halogen bond length is far greater than that of the sodium bond. In all triads studied, a favorable cooperativity is found with values that range between -0.30 and - 1.72 kcal/mol. It is revealed that NMR parameters at the site of the nitrogen atom of the NCNa molecule can be regarded as a good description to quantify the degree of cooperative effects in the NCX ... NCNa ... NCY systems. The nature of halogen bond and sodium bond interactions of the complexes is analyzed using parameters derived from the quantum theory of atoms in molecules methodology and energy decomposition analysis. Key words: cooperativity, halogen bond, sodium bond, NMR, ab initio. Des calculs de chimie quantique sont effectues pour etudier la cooperativite et les effets de substituent au niveau des interactions des liaisons halogene et sodium dans les complexes NCX ... NCNa ... NCY, ou X = F, Cl, Br, I et Y = H, F, OH. Ces effets sont analyses du point de vue de la geometrie d'equilibre, de l'energie d'interaction, des parametres de resonance magnetique nucleaire (RMN) [sup.15]N et de l'analyse de la densite electronique des complexes au niveau MP2/aug-cc-pVTZ. Les longueurs des liaisons X ... N et Na ... N dans les systemes ternaires sont toujours inferieures a celles des dyades correpondantes. Dans chaque triade, la longueur de la liaison halogene diminue beaucoup plus que celle de la liaison sodium. Dans toutes les triades etudiees, une cooperativite favorable est observee, les valeurs se situant entre -,3 et -1,72 kcal/mol. Il semble que les parametres de RMN a l'emplacement de l'atome d'azote de la molecule de NCNa puissent etre consideres comme une bonne description permettant de quantifier le degre des effets cooperatifs dans les systemes NCX ... NCNa ... NCY. La nature des interactions des liaisons halogenes et sodium des complexes est analysee a l'aide des parametres decoulant de la methodologie de la theorie quantique des atomes dans les molecules et de l'analyse de la decomposition energetique. [Traduit par la Redaction] Mots-cles: cooperativite, liaison halogene, liaison sodium, RMN, ab initio., Introduction There is now a growing awareness of the importance of noncovalent interactions, due to their extensive potential applications in many fields of chemistry and biochemistry. (1,2) Among the various [...]