Identification of conjugation positions of urinary glucuronidated vitamin D3 metabolites by LC/ESI–MS/MS after conversion to MS/MS‐fragmentable derivatives

A liquid chromatography/electrospray ionization–tandem mass spectrometry‐based method was developed for the identification of the conjugation positions of the monoglucuronides of 25‐hydroxyvitamin D₃ [25(OH)D₃] and 24,25‐dihydroxyvitamin D₃ [24,25(OH)₂D₃] in human urine. The method employed derivatization with 4‐(4‐dimethylaminophenyl)‐1,2,4‐triazoline‐3,5‐dione to convert the glucuronides into fragmentable derivatives, which provided useful product ions for identifying the conjugation positions during the MS/MS. The derivatization also enhanced the assay sensitivity and specificity for urine sample analysis. The positional isomeric monoglucuronides, 25(OH)D₃‐3‐ and ‐25‐glucuronides, or 24,25(OH)₂D₃‐3‐, ‐24‐ and ‐25‐glucuronides, were completely separated from each other under the optimized LC conditions. Using this method, the conjugation positions were successfully determined to be the C3 and C24 positions for the glucuronidated 25(OH)D₃ and 24,25(OH)₂D₃, respectively. The 3‐glucuronide was not present for 24,25(OH)₂D₃, unlike 25(OH)D₃, thus we found that selective glucuronidation occurs at the C24‐hydroxy group for 24,25(OH)₂D₃.     

4‐(2‐Hydroxyphenyl)‐2‐phenyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepine and the 2‐(2,3‐dimethoxyphenyl)‐, 2‐(3,4‐dimethoxyphenyl)‐ and 2‐(2,5‐dimethoxyphenyl)‐substituted derivatives

The 1,5‐benzodiazepine ring system exhibits a puckered boat‐like conformation for all four title compounds [4‐(2‐hydroxyphenyl)‐2‐phenyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₁H₁₈N₂O, (I), 2‐(2,3‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (II), 2‐(3,4‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (III), and 2‐(2,5‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (IV)]. The stereochemical correlation of the two C₆ aromatic groups with respect to the benzodiazepine ring system is pseudo‐equatorial–equatorial for compounds (I) (the phenyl group), (II) (the 2,3‐dimethoxyphenyl group) and (III) (the 3,4‐dimethoxyphenyl group), while for (IV) (the 2,5‐dimethoxyphenyl group) the system is pseudo‐axial–equatorial. An intramolecular hydrogen bond between the hydroxyl OH group and a benzodiazepine N atom is present for all four compounds and defines a six‐membered ring, whose geometry is constant across the series. Although the molecular structures are similar, the supramolecular packing is different; compounds (I) and (IV) form chains, while (II) forms dimeric units and (III) displays a layered structure. The packing seems to depend on at least two factors: (i) the nature of the atoms defining the hydrogen bond and (ii) the number of intermolecular interactions of the types O—H...O, N—H...O, N—H...π(arene) or C—H...π(arene).     

Dual Amplified Electrochemical Immunosensor for Hepatitis B Virus Surface Antigen Detection Using Hemin/G‐Quadruplex Immobilized onto Fe3O4‐AuNPs or (Hemin‐Amino‐rGO‐Au) Nanohybrid

A sensitive electrochemical immunosensor for Hepatitis B virus surface antigen (HBsAg) detection was fabricated based on hemin/G‐quadruplex interlaced onto Fe₃O₄‐AuNPs or hemin ‐amino‐reduced graphene oxide nanocomposite (H‐amino‐rGO‐Au). G‐quadruplex DNAzyme, which is composed of hemin and guanine‐rich nucleic acid, is an effective signal amplified tool for its outstanding peroxidase activity and Fe₃O₄‐AuNPs or (H‐amino‐rGO‐Au) nanocomposites with quasi‐enzyme activity provide appropriate support for the immobilization of hemin/G‐quadruplex. The target protein was sandwiched between the primary antibody immobilized on the GO and secondary antibody immobilized on the Fe₃O₄‐AuNPs or (H‐amino‐rGO‐Au) nanocomposites and glutaraldehyde was used as linking agent for the immobilization of primary antibody on the surface of GO. Both Fe₃O₄‐AuNPs and H‐amino‐rGO‐Au nanocomposite and also hemin/G‐quadruplex can cooperate the electrocatalytic reduction of H₂O₂ in the presence of methylene blue as mediator. The proposed immunosensor has a wide linear dynamic range of 0.1 pg/ml to 300 pg/ml with a detection limit of 60 fg/ml when Fe₃O₄‐AuNPs was used for immobilization of hemin/G‐quadruplex, while the dynamic range and DL were 0. 1–1000 pg/mL and 10 fg/mL, respectively in the presence of H‐amino‐rGO‐ Au nanocomposite as platform for immobilizing of hemin/G‐quadruplex. The proposed immunosensor was also used for analysis of HBsAg in spiked human serum samples with satisfactory results.     

Biphenyl‐ and phenylnaphthalenyl‐substituted 1H‐imidazole‐4,5‐dicarbonitrile catalysts for the coupling reaction of nucleoside methyl phosphonamidites

Crystal structures are reported for three substituted 1H‐imidazole‐4,5‐dicarbonitrile compounds used as catalysts for the coupling reaction of nucleoside methyl phosphonamidites, namely 2‐(3′,5′‐dimethylbiphenyl‐2‐yl)‐1H‐imidazole‐4,5‐dicarbonitrile, C₁₉H₁₄N₄, (I), 2‐(2′,4′,6′‐trimethylbiphenyl‐2‐yl)‐1H‐imidazole‐4,5‐dicarbonitrile, C₂₀H₁₆N₄, (II), and 2‐[8‐(3,5‐dimethylphenyl)naphthalen‐1‐yl]‐1H‐imidazole‐4,5‐dicarbonitrile, C₂₃H₁₆N₄, (III). The asymmetric unit of (I) contains two independent molecules with similar conformations. There is steric repulsion between the imidazole group and the terminal phenyl group in all three compounds, resulting in the nonplanarity of the molecules. The naphthalene group of (III) shows significant deviation from planarity. The C—N bond lengths in the imidazole rings range from 1.325 (2) to 1.377 (2) Å. The molecules are connected into zigzag chains by intermolecular N—H...N_imidazole [for (I)] or N—H...·N_cyano [for (II) and (III)] hydrogen bonds.     

Monitoring structural transformations in crystals. 13. On photocyclization in 2,3,4,5,6‐pentamethylbenzophenone, 1,3‐diphenylbutan‐1‐one and 2,4,6‐triisopropyl‐4′‐methoxybenzophenone

The geometrical parameters governing the potential for the photocyclization reaction occurring in crystals of 2,3,4,5,6‐pentamethylbenzophenone, C₁₈H₂₀O, (I), 1,3‐diphenylbutan‐1‐one, C₁₆H₁₆O, (II), and 2,4,6‐triisopropyl‐4′‐methoxybenzophenone, C₂₃H₃₀O₂, (IV), have been evaluated. Compound (IV) undergoes photocyclization but (I) and (II) do not, despite the fact that their geometrical parameters appear equally favourable for reaction. The structure of the partially reacted crystal of the photoactive compound, i.e. 2,4,6‐triisopropyl‐4′‐methoxybenzophenone–3,5‐diisopropyl‐7‐(4‐methoxyphenyl)‐8,8‐dimethylbicyclo[4.2.0]octa‐1,3,5‐trien‐7‐ol (9/1), 0.90C₂₃H₃₀O₂·0.10C₂₃H₃₀O₂, (III), was also determined, providing structural evidence for the reactivity of the compound. It has been found that the carbonyl group of the photoactive compound reacts with one of the two o‐isopropyl groups. The study has shown that the intramolecular geometrical parameters are not the only factors influencing the reactivity of compounds in crystals.     

A water soluble macromolecular nanobox having porphyrinic walls as a large host for giant guests

Cyclic tetra{5,15‐di‐[p(ω‐methoxypolyethyleneoxy)phenyl]‐10,20‐[p‐oxyphenyl] methylen porphyrin}, cy‐[O‐(H₂‐PTPEG₂)‐O‐CH₂‐]₄ , a water soluble macromolecule consisting of four porphyrin units [each with two long ω‐methoxypolyethyleneoxy (PEG) branches bound on its peripheral positions] linked by means of four methylenoxy bridges, was prepared by an interfacial etherification reaction. Structural and spectroscopic characterization of cy‐[O‐(H₂‐PTPEG₂)‐O‐CH₂‐]₄ and of its cobalt‐derivative {cy‐[O‐(Co‐PTPEG₂)‐O‐CH₂‐]₄} was performed by means of MALDI‐TOF mass spectrometry, NMR, UV–vis, and circular dichroism spectroscopy. The data obtained from the cy‐[O‐(Co‐PTPEG₂)‐O‐CH₂‐]₄/Gramicidin‐S mixture showed that some evident spectral changes were compatible with the formation of a supramolecular structure between the porphyrinic nanobox and the Gramicidin S (a polypeptide having a relevant pharmacological importance). These preliminary data highlight how cy‐[O‐(H₂‐PTPEG₂)‐O‐CH₂‐]₄ and/or its metalled derivatives, for their both chemical composition and structural arrangement, have promising properties for applications as a drug carrier in aqueous media. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Surface-modified TiO(2) nanoparticles as affinity probes and as matrices for the rapid analysis of phosphopeptides and proteins in MALDI-TOF-MS

We utilized three different types of TiO₂ nanoparticles (NPs) namely TiO₂‐dopamine, TiO₂‐CdS and bare TiO₂ NPs as multifunctional nanoprobes for the rapid enrichment of phosphopeptides from tryptic digests of α‐ and β‐casein, milk and egg white using a simplified procedure in MALDI‐TOF‐MS. Surface‐modified TiO₂ NPs serve as effective matrices for the analysis of peptides (gramicidin D, HW6, leucine‐enkephalin and methionine‐enkephalin) and proteins (cytochrome c and myoglobin) in MALDI‐TOF‐MS. In the surface‐modified TiO₂ NPs‐based MALDI mass spectra of these analytes (phosphopetides, peptides and proteins), we found that TiO₂‐dopamine and bare TiO₂ NPs provided an efficient platform for the selective and rapid enrichment of phosphopeptides and TiO₂‐CdS NPs efficiently acted as the matrix for background‐free detection of peptides and proteins with improved resolution in MALDI‐MS. We found that the upper detectable mass range is 17 000 Da using TiO₂‐CdS NPs as the matrix. The approach is simple and straightforward for the rapid analysis of phosphopeptides, peptides and proteins by MALDI‐MS in proteome research.     

Two succinic acid derivatives of 2‐ethyl‐6‐methylpyridin‐3‐ol

Crystals of bis(2‐ethyl‐3‐hydroxy‐6‐methylpyridinium) succinate–succinic acid (1/1), C₈H₁₂NO⁺·0.5C₄H₄O₄²⁻·0.5C₄H₆O₄, (I), and 2‐ethyl‐3‐hydroxy‐6‐methylpyridinium hydrogen succinate, C₈H₁₂NO⁺·C₄H₅O₄⁻, (II), were obtained by reaction of 2‐ethyl‐6‐methylpyridin‐3‐ol with succinic acid. The succinate anion and succinic acid molecule in (I) are located about centres of inversion. Intermolecular O—H...O, N—H...O and C—H...O hydrogen bonds are responsible for the formation of a three‐dimensional network in the crystal structure of (I) and a two‐dimensional network in the crystal structure of (II). Both structures are additionally stabilized by π–π interactions between symmetry‐related pyridine rings, forming a rod‐like cationic arrangement for (I) and cationic dimers for (II).     

The influence of sulfur substituents on the molecular geometry and packing of thio derivatives of N‐methylphenobarbital

The room‐temperature crystal structures of four new thio derivatives of N‐methylphenobarbital [systematic name: 5‐ethyl‐1‐methyl‐5‐phenylpyrimidine‐2,4,6(1H,3H,5H)‐trione], C₁₃H₁₄N₂O₃, are compared with the structure of the parent compound. The sulfur substituents in N‐methyl‐2‐thiophenobarbital [5‐ethyl‐1‐methyl‐5‐phenyl‐2‐thioxo‐1,2‐dihydropyrimidine‐4,6(3H,5H)‐dione], C₁₃H₁₄N₂O₂S, N‐methyl‐4‐thiophenobarbital [5‐ethyl‐1‐methyl‐5‐phenyl‐4‐thioxo‐3,4‐dihydropyrimidine‐2,6(1H,5H)‐dione], C₁₃H₁₄N₂O₂S, and N‐methyl‐2,4,6‐trithiophenobarbital [5‐ethyl‐1‐methyl‐5‐phenylpyrimidine‐2,4,6(1H,3H,5H)‐trithione], C₁₃H₁₄N₂S₃, preserve the heterocyclic ring puckering observed for N‐methylphenobarbital (a half‐chair conformation), whereas in N‐methyl‐2,4‐dithiophenobarbital [5‐ethyl‐1‐methyl‐5‐phenyl‐2,4‐dithioxo‐1,2,3,4‐tetrahydropyrimidine‐6(5H)‐one], C₁₃H₁₄N₂OS₂, significant flattening of the ring was detected. The number and positions of the sulfur substituents influence the packing and hydrogen‐bonding patterns of the derivatives. In the cases of the 2‐thio, 4‐thio and 2,4,6‐trithio derivatives, there is a preference for the formation of a ring motif of the R₂²(8) type, which is also a characteristic of N‐methylphenobarbital, whereas a C(6) chain forms in the 2,4‐dithio derivative. The preferences for hydrogen‐bond formation, which follow the sequence of acceptor position 4 > 2 > 6, confirm the differences in the nucleophilic properties of the C atoms of the heterocyclic ring and are consistent with the course of N‐methylphenobarbital thionation reactions.     

Interaction identification of Zif268 and TATAZF proteins with GC‐/AT‐rich DNA sequence: A theoretical study

Molecular dynamics (MD) simulations for Zif268 (a zinc‐finger‐protein binding specifically to the GC‐rich DNA)‐d(A₁G₂C₃G₄T₅G₆G₇G₈C₉A₁₀C₁₁)₂ and TATA_ZF (a zinc‐finger‐protein recognizing the AT‐rich DNA)‐d(A₁C₂G₃C₄T₅A₆T₇A₈A₉A₁₀A₁₁G₁₂G₁₃)₂ complexes have been performed for investigating the DNA binding affinities and specific recognitions of zinc fingers to GC‐rich and AT‐rich DNA sequences. The binding free energies for the two systems have been further analyzed by using the molecular mechanics Poisson‐Boltzmann surface area (MM‐PBSA) method. The calculations of the binding free energies reveal that the affinity energy of Zif268‐DNA complex is larger than that of TATA_ZF‐DNA one. The affinity between the zinc‐finger‐protein and DNA is mainly driven by more favorable van‐der‐Waals and nonpolar/solvation interactions in both complexes. However, the affinity energy difference of the two binding systems is mainly caused by the difference of van‐der‐Waals interactions and entropy components. The decomposition analysis of MM‐PBSA free energies on each residue of the proteins predicts that the interactions between the residues with the positive charges and DNA favor the binding process; while the interactions between the residues with the negative charges and DNA behave in the opposite way. The interhydrogen‐bonds at the protein‐DNA interface and the induced intrafinger hydrogen bonds between the residues of protein for the Zif268‐DNA complex have been identified at some key contact sites. However, only the interhydrogen‐bonds between the residues of protein and DNA for TATA_ZF‐DNA complex have been found. The interactions of hydrogen‐bonds, electrostatistics and van‐der‐Waals type at some new contact sites have been identified. Moreover, the recognition characteristics of the two studied zinc‐finger‐proteins have also been discussed. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011     

Similar sulfonamides with different crystal structures: sulfasymazine and sulfatriazine

The crystal structures of 4‐amino‐N‐(4,6‐diethyl‐1,3,5‐triazin‐2‐yl)benzenesulfonamide, C₁₃H₁₇N₅O₂S, and 4‐amino‐N‐(4,6‐dimethoxy‐1,3,5‐triazin‐2‐yl)benzenesulfonamide, C₁₁H₁₃N₅O₄S, also known as sulfasymazine and sulfatriazine, respectively, are dominated by hydrogen‐bond interactions. All three potential hydrogen‐bond donors are employed in each case, resulting in a three‐dimensional network for sulfasymazine, while an entirely different hydrogen‐bonded layer structure is obtained for sulfatriazine. This study demonstrates the versatile nature of the hydrogen‐bonding capabilities in sulfonamides, even in structurally very similar molecules.     

Magnetic iron(III)‐based framework composites for the magnetic solid‐phase extraction of fungicides from environmental water samples

We adopted a facile hydrofluoric acid‐free hydro‐/solvothermal method for the preparation of four magnetic iron(III)‐based framework composites (MIL‐101@Fe₃O₄‐COOH, MIL‐101‐NH₂@Fe₃O₄‐COOH, MIL‐53@Fe₃O₄‐COOH, and MIL‐53‐NH₂@Fe₃O₄‐COOH). The obtained four magnetic iron(III)‐based framework composites were applied to magnetic separation and enrichment of the fungicides (prochloraz, myclobutanil, tebuconazole, and iprodione) from environmental samples before high‐performance liquid chromatographic analysis. MIL‐101‐NH₂@Fe₃O₄‐COOH showed more remarkable pre‐concentration ability for the fungicides as compared to the other three magnetic iron(III)‐based framework composites. The extraction parameters affecting enrichment efficiency including extraction time, sample pH, elution time, and the desorption solvent were investigated and optimized. Under the optimized conditions, the standard curve of correlation coefficients were all above 0.991, the limits of detection were 0.04–0.4 μg/L, and the relative standard deviations were below 10.2%. The recoveries of two real water samples ranged from 71.1–99.1% at the low spiking level (30 μg/L). Therefore, the MIL‐101‐NH₂@Fe₃O₄‐COOH composites are attractive for the rapid and efficient extraction of fungicides from environmental water samples.     

A Ga‐MIL‐53‐type Framework based on 1,4‐Phenylenediacetate Showing Subtle Flexibility

The new MOF Ga‐MIL‐53‐PDA [Ga(OH)(O₂C‐C₈H₈‐CO₂)] · H₂O ( 1 ) was synthesized by a hydrothermal reaction of gallium nitrate, 1,4‐phenylenediacetic acid (H₂PDA) and sodium hydroxide at 100 °C for 24 h. The product is a structural analogue of the archetypical MIL‐53 framework. Its crystal structure was determined by Rietveld refinement of powder X‐ray diffraction (PXRD) data. Furthermore 1,4‐phenylenedipropionic acid (H₂PDP) was employed for further synthesis, which resulted in the dense layered coordination polymers [Ga₂(OH)₄(O₂C‐C₁₀H₁₂‐CO₂)] ( 2 ) and [Ga(OH)(O₂C‐C₁₀H₁₂‐CO₂)] ( 3 ), for which accurate structural models could be established. All compounds were fully characterized and tested regarding potential breathing behavior. Most remarkably, Ga‐MIL‐53‐PDA showed a subtle flexibility upon de/‐rehydration also confirming its porosity, but no drastic structural changes were observed.     

Bis(hinokitiolato)copper(II): modification (III)

Bis(hinokitiolato)copper(II), Cu(hino)₂, exhibits both antibacterial and antiviral properties, and has been previously shown to exist in two modifications. A third modification has now been confirmed, namely tetrakis(μ₂‐3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olato)bis(3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olato)tricopper(II)–bis(μ₂‐3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olato)bis[(3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olato)copper(II)] (1/1), [Cu(C₁₀H₁₁O₂)₂]₃·[Cu(C₁₀H₁₁O₂)₂]₂, where 3‐isopropyl‐7‐oxocyclohepta‐1,3,5‐trien‐1‐olate is the systematic name for the hinokitiolate anion. This new modification is composed of discrete [cis‐Cu(hino)₂]₂[trans‐Cu(hino)₂] trimers and [cis‐Cu(hino)₂]₂ dimers. The Cu atoms are bridged by μ₂‐O atoms from the hinokitiolate ligands to give distorted square‐pyramidal and distorted octahedral Cu^II coordination environments. Hence, the Cu^II environments are CuO₅/CuO₆/CuO₅ for the trimer and CuO₅/CuO₅ for the dimer. Each trimer and dimer has crystallographically imposed inversion symmetry. The trimer has never been observed before, the dimer has been seen only once before, and the combination of the two together in the same lattice is unprecedented. The CuO₅ cores exhibit four strong basal Cu—O bonds [1.915 (2)–1.931 (2) Å] and one weak apical Cu—O bond [2.652 (2)–2.658 (2) Å]. The CuO₆ core exhibits four strong equatorial Cu—O bonds [1.922 (2)–1.929 (2) Å] and two very weak axial Cu—O bonds [2.911 (3) Å]. The bite angles for the chelating hinokitiolate ligands range from 83.13 (11) to 83.90 (10)°.     

Highly active copolymerization of ethylene with 10‐undecen‐1‐ol using phenoxy‐based zirconium/methylaluminoxane catalysts

Activated with methylaluminoxane (MAO), phenoxy‐based zirconium complexes bis[(3‐^tBu‐C₆H₃‐2‐O)‐CH?NC₆H₅]ZrCl₂, bis[(3,5‐di‐^tBu‐C₆H₂‐2‐O)‐PhC?NC₆H₅] ZrCl₂, and bis[(3,5‐di‐^tBu‐C₆H₂‐2‐O)‐PhC?N(2‐F‐C₆H₄)]ZrCl₂ for the first time have been used for the copolymerization of ethylene with 10‐undecen‐1‐ol. In comparison with the conventional metallocene, the phenoxy‐based zirconium complexes exhibit much higher catalytic activities [>10⁷ g of polymer (mol of catalyst)^?1 h^?1]. The incorporation of 10‐undecen‐1‐ol into the copolymers and the properties of the copolymers are strongly affected by the catalyst structure. Among the three catalysts, complex c is the most favorable for preparing higher molecular weight functionalized polyethylene containing a higher content of hydroxyl groups. Studies on the polymerization conditions indicate that the incorporated commoner content in the copolymers mainly depends on the comonomer concentration in the feed. The catalytic activity is slightly affected by the Al_(MAO)/Zr molar ratio but decreases greatly with an increase in the polymerization temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5944–5952, 2005     

Three monoalkoxy‐substituted nido‐platinaboranes: [(PPh3)2PtB10H11‐8‐(OCH3)], [(PPh3)2PtB10H11‐8‐{OCH(CH3)2}] and [(PPh3)2PtB10H10‐9‐{OCH(CH3)2}]

Each of the title compounds, 8‐methoxy‐7,7‐bis­(tri­phenyl­phosphine‐P)‐8,9:10,11‐di‐μH‐7‐platina‐nido‐undecaborane di­chloro­methane hemisolvate, [Pt(CH₁₄B₁₀O)(C₁₈H₁₅P)₂]·0.5CH₂Cl₂, (I), 8‐isopropoxy‐7,7‐bis­(tri­phenyl­phosphine‐P)‐8,9:10,11‐di‐μH‐7‐platina‐nido‐undecaborane di­chloro­methane solvate, [Pt(C₃H₁₈B₁₀O)(C₁₈H₁₅P)₂]·CH₂Cl₂, (II), and 9‐isopropoxy‐7,7‐bis­(tri­phenyl­phosphine‐P)‐8,9:10,11‐di‐μH‐7‐platina‐nido‐undecaborane di­chloro­methane solvate, [Pt(C₃H₁₈B₁₀O)(C₁₈H₁₅P)₂]·CH₂Cl₂, (III), has an 11‐vertex nido polyhedral skeleton, with the 7‐platinum centre ligating to two exo‐polyhedral PPh₃ groups and an alkoxy‐substituted polyhedral borane ligand. Compounds (II) and (III) are isomers. The Pt—B distances are in the range 2.214 (7)–2.303 (7) Å for (I), 2.178 (16)–2.326 (16) Å for (II) and 2.205 (6)–2.327 (6) Å for (III).     

Luminescent properties of three structures built from 3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olate and cadmium

Yellow–orange tetraaquabis(3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olato‐κN³)cadmium(II) dihydrate, [Cd(C₈HN₄O₂)₂(H₂O)₄]·2H₂O, (I), and yellow tetraaquabis(3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olato‐κN³)cadmium(II) 1,4‐dioxane solvate, [Cd(C₈HN₄O₂)₂(H₂O)₄]·C₄H₈O₂, (II), contain centrosymmetric mononuclear Cd²⁺ coordination complex molecules in different conformations. Dark‐red poly[[decaaquabis(μ₂‐3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olato‐κ²N:N′)bis(μ₂‐3‐cyano‐4‐dicyanomethylene‐1H‐pyrrole‐2,5‐diolato‐κ²N:N′)tricadmium] hemihydrate], [Cd₃(C₈HN₄O₂)₂(C₈N₄O₂)₂(H₂O)₁₀]·0.5H₂O, (III), has a polymeric two‐dimensional structure, the building block of which includes two cadmium cations (one of them located on an inversion centre), and both singly and doubly charged anions. The cathodoluminescence spectra of the crystals are different and cover the wavelength range from UV to red, with emission peaks at 377 and 620 nm for (III), and at 583 and 580 nm for (I) and (II), respectively.     

Rational Design of Specific Recognition Molecules for Simultaneously Monitoring of Endogenous Polysulfide and Hydrogen Sulfide in the Mouse Brain

A biosensor was created for the simultaneous monitoring of endogenous H₂S_n and H₂S in mouse brains and exploring their roles in activation of the TRPA1 channel under two types of brain disease models: ischemia and Alzheimer's disease (AD). Based on DFT calculations and electrochemical measurements, two probes, 3,4‐bis((2‐fluoro‐5‐nitrobenzoyl)oxy)‐benzoic acid (M_PS‐1) and N‐(4‐(2,5‐dinitrophenoxy) phenyl)‐5‐(1, 2‐dithiolan‐3‐yl)pentanamide (M_HS‐1), were synthesized for specific recognition of H₂S_n and H₂S. Through co‐assembly of the two probes at the mesoporous gold film with good anti‐biofouling ability and electrocatalytic activity, this microsensor showed high selectivity for H₂S_n and H₂S against potential biological interferences. The biosensor can simultaneously determine the concentration of H₂S_n from 0.2 to 50 μm , as well as that of H₂S from 0.2 to 40 μm . The expression of TRPA1 protein positively correlated with levels of H₂S_n under both ischemia and AD.     

6‐Propyl‐2‐thiouracil versus 6‐methoxymethyl‐2‐thiouracil: enhancing the hydrogen‐bonded synthon motif by replacement of a methylene group with an O atom

The understanding of intermolecular interactions is a key objective of crystal engineering in order to exploit the derived knowledge for the rational design of new molecular solids with tailored physical and chemical properties. The tools and theories of crystal engineering are indispensable for the rational design of (pharmaceutical) cocrystals. The results of cocrystallization experiments of the antithyroid drug 6‐propyl‐2‐thiouracil (PTU) with 2,4‐diaminopyrimidine (DAPY), and of 6‐methoxymethyl‐2‐thiouracil (MOMTU) with DAPY and 2,4,6‐triaminopyrimidine (TAPY), respectively, are reported. PTU and MOMTU show a high structural similarity and differ only in the replacement of a methylene group (–CH₂–) with an O atom in the side chain, thus introducing an additional hydrogen‐bond acceptor in MOMTU. Both molecules contain an ADA hydrogen‐bonding site (A = acceptor and D = donor), while the coformers DAPY and TAPY both show complementary DAD sites and therefore should be capable of forming a mixed ADA/DAD synthon with each other, i.e. N—H…O, N—H…N and N—H…S hydrogen bonds. The experiments yielded one solvated cocrystal salt of PTU with DAPY, four different solvates of MOMTU, one ionic cocrystal of MOMTU with DAPY and one cocrystal salt of MOMTU with TAPY, namely 2,4‐diaminopyrimidinium 6‐propyl‐2‐thiouracilate–2,4‐diaminopyrimidine–N,N‐dimethylacetamide–water (1/1/1/1) (the systematic name for 6‐propyl‐2‐thiouracilate is 6‐oxo‐4‐propyl‐2‐sulfanylidene‐1,2,3,6‐tetrahydropyrimidin‐1‐ide), C₄H₇N₄⁺·C₇H₉N₂OS⁻·C₄H₆N₄·C₄H₉NO·H₂O, (I), 6‐methoxymethyl‐2‐thiouracil–N,N‐dimethylformamide (1/1), C₆H₈N₂O₂S·C₃H₇NO, (II), 6‐methoxymethyl‐2‐thiouracil–N,N‐dimethylacetamide (1/1), C₆H₈N₂O₂S·C₄H₉NO, (III), 6‐methoxymethyl‐2‐thiouracil–dimethyl sulfoxide (1/1), C₆H₈N₂O₂S·C₂H₆OS, (IV), 6‐methoxymethyl‐2‐thiouracil–1‐methylpyrrolidin‐2‐one (1/1), C₆H₈N₂O₂S·C₅H₉NO, (V), 2,4‐diaminopyrimidinium 6‐methoxymethyl‐2‐thiouracilate (the systematic name for 6‐methoxymethyl‐2‐thiouracilate is 4‐methoxymethyl‐6‐oxo‐2‐sulfanylidene‐1,2,3,6‐tetrahydropyrimidin‐1‐ide), C₄H₇N₄⁺·C₆H₇N₂O₂S⁻, (VI), and 2,4,6‐triaminopyrimidinium 6‐methoxymethyl‐2‐thiouracilate–6‐methoxymethyl‐2‐thiouracil (1/1), C₄H₈N₅⁺·C₆H₇N₂O₂S⁻·C₆H₈N₂O₂S, (VII). Whereas in (I) only an AA/DD hydrogen‐bonding interaction was formed, the structures of (VI) and (VII) both display the desired ADA/DAD synthon. Conformational studies on the side chains of PTU and MOMTU also revealed a significant deviation for cocrystals (VI) and (VII), leading to the desired enhancement of the hydrogen‐bond pattern within the crystal.     

Excess Molar Volumes and Viscosities for Binary Mixtures of 1-Alkoxypropan-2-ols with 1-Butanol, and 2-Butanol at 298.15 K and Atmospheric Pressure

Excess molar volumes Vm^E and kinematic viscosities v have been measured as a function of composition for binary mixtures of propylene glycol monomethyl ether （1-methoxy-2-propanol）, MeOCH2CH（OH）Me, propylene glycol monoethyl ether （1-ethoxy-2-propanol）, EtOCH2CH（OH）Me, propylene glycol monopropyl ether （1-propoxy-2-propanol）, PrOCH2CH（OH）Me, propylene glycol monobutyl ether （1-butoxy-2-propanol）, BuOCH2CH（OH）Me, and propylene glycol tert-butyl ether （1-tert-butoxy-2-propanol）, t-BuOCH2CH（OH）Me with 1-butanol, and 2-butanol, at 298.15 K and atmospheric pressure. The excess molar volumes are negative across the entire range of composition for all the systems with 1-butanol, and positive for the systems 2-butanol＋ 1-methoxy-2-propanol, and ＋1-propoxy-2-propanol, negative for the systems 2-butanol＋1-butoxy-2-propanol, and change sign for the systems 2-butanol＋ 1-ethoxy-2-propanol, and ＋ 1-tert-butoxy-2-propanol. From the experimental data, the deviation in dynamic viscosity η from ∑χiηi has been calculated. Both excess molar volumes and viscosity deviations have been correlated using a Redlich-Kister type polynomial equation by the method of least-squares for the estimation of the binary coefficients and the standard errors.