Hyperpolarized 13C NMR Spectroscopy of Urine Samples at Natural Abundance by Quantitative Dissolution Dynamic Nuclear Polarization

Hyperpolarized nuclear magnetic resonance (NMR) offers an ensemble of methods that remarkably address the sensitivity issues of conventional NMR. Dissolution Dynamic Nuclear Polarization (d-DNP) provides a unique and general way to detect ¹³C NMR signals with a sensitivity enhanced by several orders of magnitude. The expanding application scope of d-DNP now encompasses the analysis of complex mixtures at natural ¹³C abundance. However, the application of d-DNP in this area has been limited to metabolite extracts. Here, we report the first d-DNP-enhanced ¹³C NMR analysis of a biofluid -urine- at natural abundance, offering unprecedented resolution and sensitivity for this challenging type of sample. We also show that accurate quantitative information on multiple targeted metabolites can be retrieved through a standard addition procedure.     

Effect of pressure on the solubility of naphthalene in water at 25°C

Solubility of naphthalene in water was measured at 25°C and pressures up to 200 MPa. The solubility decreased with increasing pressure. From the pressure coefficient of the solubility, the volume change V accompanying the dissolution was estimated as 13.8±0.4 cm ³ -mol ^–1 . Further we estimated the volume change V _CH accompanying hydrophobic hydration as –0.1±0.6 cm ³ -mol ^–1 using the V value, the molar volume of crystalline naphthalene, and the partial molar volume of naphthalene in n-heptane. This V _CH is much larger (i.e., less negative) than that for hydrophobic hydration of alkyl-chain compounds and suggests that the hydration structure of naphthalene differs from that of alkyl-chain compounds.     

Influences of Broensted Acidic Sites in H[Al] ZSM—5 on Polarization and Electronegativity of Ethene Studied by Molecular Dynamics

Molecular dynamics simulation has been performed for studying the polarization and electronegativity of ethene molecules near Broensted acidic sites in H[Al] ZSM-5.The result shows that the molecules are polarized most at the edges of intersections and least at the segments of channels.On the contrary,the highest global molecular electronegativity is found at the centers of channel segments.Al substitution slightly increases the molecular dipole moment,but hardly affects the molecular electronegativity.Broensted acidic proton decreases the dipolemoment of guest molecule,but increases the molecular electtronegativity.     

Vibrational spectra of tropylium tetrahaloborates [C7H7] [BX4] (X  Br or I)

Raman and i.r. studies of the title compounds, which are salts of the planar D_7h tropylium cation, provide complete sets of vibrational frequencies for the tetrahaloborate anions, including Raman data for [BI₄]⁻ for which ν₁(a₁) = 169, ν₂(e) = 83, ν₃(t₂) = 515 (¹¹B), 543 (¹⁰B) and ν₄(t₂) = 117 cm⁻¹.     

The formation of acenaphthylene on pyrolysis of 8-methyl-1,2-dihydrocyclobuta[α] naphthalene-1,2-dione: A 13C labelling study

Flash vacuum pyrolysis of the 1-¹³C labelled dione (4) at 730°C/0.02 Torr gives acenaphthylene labelled predominantly at C4 and C1, as predicted for the intermediacy of labelled carbene (7).     

Copper complexes with N-allylisoquinolinium halides: Synthesis and crystal structures of [C9H7N(C3H5)]2CuIICl2.86Br1.14, [C9H7N(C3H5)CuIBr2] · H2O, and [C9H7N(C3H5)CuIBr2]

Crystals of the copper bromide complexes with N-allylisoquinolinium halides of the composition [C₉H₇N(C₃H₅)]₂Cu^IICl_2.86Br_1.14 (I), [C₉H₇N(C₃H₅)]Cu^IBr₂ · H₂O (II), and [C₉H₇N(C₃H₅)]Cu^IBr₂ (III) are prepared by ac electrochemical synthesis, and their structures are studied by X-ray diffraction analysis (DARCh-1 (for I) and KUMA/CCD (for II and III) diffractometers). The crystals of compound I are monoclinic: space group P2₁/n, a = 15.053(5) Å, b = 10.486(4) Å, c = 17.179(10) Å, γ = 109.77(3)°, V = 2552(4) ų, Z = 4. The crystals of complex II are triclinic: space group P $\overline 1 $ , a = 7.040(1) Å, b = 7.610(2) Å, c = 12.460(2) Å, α = 79.54(3)°, β = 86.73(3)°, γ = 89.51(1)°, V = 655.4(2) ų, Z = 2. The crystals of complex III are monoclinic: space group P2₁/n, a = 12.799(1) Å, b = 7.692(1) Å, c = 13.491(1) Å, β = 111.08(1)°, V = 1239.3(2) ų, Z = 4. The structure of compound I is built of the Cu^IIX ₄ ^2? tetrahedra and N-allylisoquinolinium cations united by the C-H···X contacts into corrugated layers. The crystal structure of π-complex II is formed of dimers of the composition [C₉H₇(C₃H₅)]₂ Cu ₂ ^I Br₄ forming layers in the direction of the z axis due to the C-H···X contacts. An important role in structure formation belongs to water molecules that cross-link the organometallic layers through the O-H···X contacts into a three-dimensional framework. When kept in the mother liquor for 6 months, the crystals of compound II transformed into crystals of compound III, whose structure consists of {[C₉H₇(C₃H₅)]₂Cu ₂ ^I Br₄} _n columns united through the C-H···Br contacts (H···Br 2.84(3)?2.92(4) Å) into a three-dimensional framework.     

Quantitative evaluation of the biosynthetic pathways leading to δ-aminolevulinic acid from the Shemin precursor glycine via the C5 pathway in Arthrobacter hyalinus by analysis of 13C-labeled coproporphyrinogen III biosynthesized from [2-13C]glycine, [1-13C]acetate, and [2-13C]acetate using 13C NMR spectroscopy

The biosynthetic pathways leading to δ-aminolevulinic acid (ALA) from the Shemin precursor glycine via the C5 pathway in Arthrobacter hyalinus were quantitatively evaluated by means of feeding experiments with [2-¹³C]glycine, sodium [1-¹³C]acetate, and sodium [2-¹³C]acetate, followed by analysis of the labeling patterns of coproporphyrinogen III (Copro’gen III) (biosynthesized from ALA) using ¹³C NMR spectroscopy. Two biosynthetic pathways leading to ALA from glycine via the C5 pathway were identified: i.e., transformation of glycine to l-serine catalyzed by glycine hydroxymethyltransferase, and glycine synthase-catalyzed catabolism of glycine to N ⁵,N ¹⁰-methylene-tetrahydrofolic acid (THF), which reacts with another molecule of glycine to afford l-serine. l-Serine is transformed to acetyl-CoA via pyruvic acid. Acetyl-CoA enters the tricarboxylic acid cycle, affording 2-oxoglutaric acid, which in turn is transformed to l-glutamic acid. The l-glutamic acid enters the C5 pathway, affording ALA in A. hyalinus. A ¹³C NMR spectroscopic comparison of the labeling patterns of Copro’gen III obtained after feeding of [2-¹³C]glycine, sodium [1-¹³C]acetate, and sodium [2-¹³C]acetate showed that [2-¹³C]glycine transformation and [2-¹³C]glycine catabolism in A. hyalinus proceed in the ratio of 52 and 48 %. The reaction of [2-¹³C]glycine and N ⁵,N ¹⁰-methylene-THF, that of glycine and N ⁵,N ¹⁰-[methylene-¹³C]methylene-THF generated from the [2-¹³C]glycine catabolism, and that of [2-¹³C]glycine and N ⁵,N ¹⁰-[methylene-¹³C]methylene-THF transformed the fed [2-¹³C]glycine to [1-¹³C]acetyl-CoA, [2-¹³C]acetyl-CoA, and [1,2-¹³C₂]acetyl-CoA in the ratios of 42, 37, and 21 %, respectively. These labeled acetyl-CoAs were then incorporated into ALA. Our results provide a quantitative picture of the pathways of biosynthetic transformation to ALA from glycine in A. hyalinus.     

Effect of Cortisol on Caspases in the Co-cultured C2C12 and 3 T3-L1 Cells

The present study was carried out to understand the effect of cortisol on caspase expression in the C2C12 and 3 T3-L1 cells under co-culture system. Cells were co-cultured by using transwell inserts with a 0.4-μm porous membrane to separate C2C12 and 3 T3-L1 preadipocyte cells. Each cell type was grown independently on the transwell plates. Following cell differentiation, inserts containing 3 T3-L1 cells were transferred to C2C12 plates and inserts containing C2C12 cells were transferred to 3 T3-L1 plates. A total of 10 μg/μl of cortisol was added to the medium. Following treatment of cortisol for 3 days, the cells in the lower well were harvested for analysis. Caspases such as caspase 3, caspase 7, and caspase 9 were selected for the analysis. qRT-PCR results indicated the significant increase in the mRNA expression of caspase 3, caspase 7, and caspase 9. Caspase 3, 7, and 9 activities were also increased in the mono- and co-cultured C2C12 and 3 T3-L1 cells. In addition, confocal microscopical investigation indicated that cortisol increases caspase expressions in the mono- and co-cultured C2C12 and 3 T3-L1 cells. Taking all these together, we concluded that the co-culture system reflects the exact effect of cortisol on caspase expression, which is quite distinct from one dimensional mono-cultured experiments.     

A Thermodynamic Study of 1-Propanol–Glycerol–H2O at 25°C: Effect of Glycerol on Molecular Organization of H2O

The excess chemical potential, partial molar enthalpy, and volume of 1-propanol were determined in ternary mixtures of 1-propanol–glycerol–H₂O at 25°C. The mole fraction dependence of all these thermodynamic functions was used to elucidate the effect of glycerol on the molecular organization of H₂O. The glycerol molecules do not exert a hydrophobic effect on H₂O. Rather, the hydroxyl groups of glycerol, perhaps by forming clusters via its alkyl backbone with hydroxyl groups pointing outward, interact with H₂O so as to reduce the characteristics of liquid H₂O. The global hydrogen bond probability and, hence, the percolation nature of the hydrogen bond network is reduced. In addition, the degree of fluctuation inherent in liquid H₂O is reduced by glycerol perhaps by participating in the hydrogen bond network via OH groups. At infinite dilution, the pair interaction coefficients in enthalpy were evaluated and these data suggest a possibility that the interaction is mediated through H₂O.     

Synthesis and Crystal Structure of [VO2（C17H11N3O2） ] [VO （C4H13N3）（C6H5N3O） ]（C2H5OH）

The reaction of VO（acac）2 with 2-hydroxyl-1-naphthaldehyde isonicotinyl hydrazone and amines （ethylenediamine or diethylenetriamine） in CH3OH yields crystals of novel vanadium compounds characterized by IR, NMR spectroscopic methods and X-ray single-crystal structure determination. Two different vanadium units exist in the crystal cell of [VO2（C17H11N3O2）][VO- （C4H13N3）（C6H5N3O）]（C2H5OH） which crystallizes in the triclinic system, space group P1 with a = 8.0104（17）, b = 13.898（3）, c = 14.955（3）A, α = 89.103（4）, β = 79.551（4）, γ = 78.352（4）°, V = 1603.3（6）A^3, Mr = 723.54, Dc = 1.499 g/cm^3, Z = 2, λ（MoKα） = 0.71073 ]A,μ= 0.644 mm^-1, F（000） = 748, the final R = 0.0547 and wR = 0.0997 for 8920 observed reflections with I 〉 2σ（I）. According to structure analysis, two different molecules are arranged in the lattice and the two vanadium atoms adopt octahedral and square pyramidal coordination geometries, respectively. The interactions between DNA and vanadium complexes have been investigated by UV-Vis absorption spectro- photometry.     

Unconventional Pathway in the Gas-Phase Synthesis of 9H-Fluorene (C13H10) via the Radical–Radical Reaction of Benzyl (C7H7) with Phenyl (C6H5)

The simplest polycyclic aromatic hydrocarbon (PAH) carrying a five-membered ring—9H-fluorene (C₁₃H₁₀)—is produced isomer-specifically in the gas phase by reacting benzyl (C₇H₇⋅) with phenyl (C₆H₅⋅) radicals in a pyrolytic reactor coupled with single photon ionization mass spectrometry. The unconventional mechanism of reaction is supported by theoretical calculations, which first produces diphenylmethane and unexpected 1-(6-methylenecyclohexa-2,4-dienyl)benzene intermediates (C₁₃H₁₂) accessed via addition of the phenyl radical to the ortho position of the benzyl radical. These findings offer convincing evidence for molecular mass growth processes defying conventional wisdom that radical-radical reactions are initiated through recombination at their radical centers. The structure of 9H-fluorene acts as a molecular building block for complex curved nanostructures like fullerenes and nanobowls providing fundamental insights into the hydrocarbon evolution in high temperature settings.     

The synthesis and crystal structure of heteronuclear complex of lanthanide with sulfo-salicylic acid [Na3YLa2(C7H3SO6)4.26H2O]n

The titled complex has been synthesized by the reaction of sodium sulfo-salicylate with lanthanum and yttrium perchlorate. The crystal structure has been determined by single crystal X-ray diffractometry. The crystal is monoclinic with space group C2/c. The unit cell parameters are as follows: a=16.289(8), b=18.323(8), c=22.044(8) A, β=106.34(2)°, V=6314(6) A3, Z=4 and Dc=1.764 g/cm3. The structure was solved by direct method. The least-square refinement based on 3776 observed reflections [F > 6σ(F)] converged to a final R=8.6% and F(000) is 3548. Yttrium ion with eight-coordinate is located in central of the molecule, the two lanthanum ions with ten-coordinate are located at the two sides of yttrium ion. There are two positions for Na in the molecule, one is in the C2 axis with six coordinate, the other one is in a general position with five-coordinate.     

Effect of oxidation of nitride coatings on corrosion properties of Ti-6Al-4V alloy in 0.9% NaCl at 40°C

The corrosion properties of Ti-6Al-4V alloy with oxidized thermodiffusion nitride coatings were investigated in isotonic 0.9% solution of NaCl at temperature of 40°C. It was shown that modification of nitride coatings by oxygen leads to a deterioration of the protective properties of nitrided surface of Ti-6Al-4V alloy. The protective properties of the alloy with nitride coatings modified by oxygen are determined by the composition of formed surface oxynitride film.      

Thermokinetics on the Reaction of Formation of the Ternary Complex Nd[（C5H8NS2）3（C12H8N2）]

Introduction The chemistry of the complexes containing lantha-nide-sulfur bond has been of substantial interest because of high performance in biological properties1 and fric-tion properties.2 In addition, they have been largely used because of their chemical and physical properties, e.g. as vulcanization accelerator.2,3 The vast investigations have been reported on preparations, characterizations and structures of these compounds,5-17 which are of great importance for illuminating the bonding…     

C–H Arylation using acyl thiourea ligands: Applications in the synthesis of 3,6-diaryl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles

Synthesis of a series of new 3,6-diaryl-[1,2,4]triazolo[3,4-b] [1,3,4]thiadiazoles(5a–o) was achieved by phophine free, C–H arylative cross-coupling of 6-aryl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles(4a–o)with suitably substituted iodoanilines using 1-(2-naphthoyl)-3-(4-bromophenyl)thiourea as a ligand.The requisite triazolothiadiazoles(4a–o) were obtained by the condensation of 4-amino-1,2,4-triazole-3-thiol(3) with suitably substituted aromatic acids in the presence of phosphoryl chloride.     

Crystal structure of [Ph4As]2[Re7C(CO)21Au(PPh3)]. Comparison of H+ and Au(PPh3)+ coordination to [Re7C(CO)21]3−

The structure of [Ph₄As]₂[Re₇C(CO)₂₁Au(PPh₃)] has been determined by X-ray crystallography. The mixed-metal cluster anion adopts a 1,4- (i.e. trans-) bicapped octahedral geometry. Solution ¹³C NMR spectra reveal that this Au(PPh₃)⁺ adduct of [Re₇C(CO)₂₁]³⁻ maintains the (1,4)-bicapped structure in solution whereas the corresponding H⁺ adduct, [HRe₇C(CO)₂₁]²⁻, displays two isomers.