10-Ethyl-acridine-2-sulfonyl Chloride: A New Derivatization Agent for Enhancement of Atmospheric Pressure Chemical Ionization of Estrogens in Urine

The extensive metabolism and treatment of low doses of estrone (E1), estradiol (E2) and estriol (E3) in preclinical animal species necessitates a sensitive analytical method to identify or quantify the estrogens in biological matrixes. In this study, a highly sensitive and specific method based on the derivatization of E1, E2 and E3 with 10-ethyl-acridine-2-sulfonyl chloride (EASC) coupled with liquid chromatography-ion-trap mass spectrometry with APCI-MS (MRM) identification of estrogens has been developed. The EASC derivatization of E1, E2 and E3 introduces an acridine functional group into estrogen molecules. The carbonyl group in EASC core results in the formation of a phenoxide negative ion by the intramolecular keto-enol isomerization that can be accepted a [H]⁺ and readily ionized in commonly used LC mobile phases. Derivatives are sufficiently stable to be efficiently analyzed by LC-APCI-MS and show an intense protonated molecular ion at m/z [M+H]⁺ in positive-ion mode. The collision-induced dissociation of molecular ion forms a distinctive product ion at m/z 222.6, corresponding to the protonated 10-ethyl-acridine moiety. The selected reaction monitoring, based on the m/z [M+H]⁺ → m/z 222.6 transitions, is highly specific for estrogen derivatives. Therefore, the facile EASC derivatization coupling with LC-APCI-MS analysis allows the development of a highly sensitive and specific method for the identification of trace levels of estrogens in urine of root vole (Microtus oeconomus Pallas).     

The electronic spectra of 10, 10-dimethylanthracen-9-one crystals: Spin—orbit/vibronic coupling in 3nπ3 states

10, 10-dimethylanthracen-9-one single crystal emission and absorption spectra have been recorded at low temperatures, as well as Raman spectra on the melt. The absorption spectra of both the lowest triplet and lowest excited singlet states clearly show the absorption origins of the three different molecular sites in the triclinic unit cell of the crystal. The emission spectra indicate that substantial spin—orbit/vibronic state mixing occurs, giving rise to transitions between the z sub-level of the lowest ³nπ³ state (T₁) and both totally and non-totally symmetric vibrations of the ground state. The preferred intensity stealing route is from T₁ (z) to S₂(¹ππ³) by spin—orbit coupling with vibronic mixing of S₃ and S₄(¹ππ³, ¹B₂).     

Mechanism of Formation of the Major Estradiol Product Ions Following Collisional Activation of the Molecular Anion in a Tandem Quadrupole Mass Spectrometer

The importance of the mass spectral product ion structure is highlighted in quantitative assays, which typically use multiple reaction monitoring (MRM), and in the discovery of novel metabolites. Estradiol is an important sex steroid whose quantitation and metabolite identification using tandem mass spectrometry has been widely employed in numerous clinical studies. Negative electrospray ionization tandem mass spectrometry of estradiol (E2) results in several product ions, including the abundant m/z 183 and 169. Although m/z 183 is one of the most abundant product ions used in many quantitative assays, the structure of m/z 183 has not been rigorously examined. We suggest a structure for m/z 183 and a mechanism of formation consistent with collision induced dissociation (CID) of E2 and several stable isotopes ([D₄]-E2, [¹³C₆]-E2, and [D₁]-E2). An additional product ion from E2, namely m/z 169, has also been examined. MS³ experiments indicated that both m/z 183 and m/z 169 originate from only E2 [M – H]^– m/z 271. These ions, m/z 183 and m/z 169, were also present in the collision induced decomposition mass spectra of other prominent estrogens, estrone (E1) and estriol (E3), indicating that these two product ions could be used to elucidate the estrogenic origin of novel metabolites. We propose two fragmentation schemes to explain the CID data and suggest a structure of m/z 183 and m/z 169 consistent with several isotopic variants and high resolution mass spectrometric measurements.      

A Distonic Radical-Ion for Detection of Traces of Adventitious Molecular Oxygen (O2) in Collision Gases Used in Tandem Mass Spectrometers

We describe a diagnostic ion that enables rapid semiquantitative evaluation of the degree of oxygen contamination in the collision gases used in tandem mass spectrometers. Upon collision-induced dissociation (CID), the m/z 359 positive ion generated from the analgesic etoricoxib undergoes a facile loss of a methyl sulfone radical [^?SO₂(CH₃); 79-Da] to produce a distonic radical cation of m/z 280. The product-ion spectrum of this m/z 280 ion, recorded under low-energy activation on tandem-in-space QqQ or QqTof mass spectrometers using nitrogen from a generator as the collision gas, or tandem-in-time ion-trap (LCQ, LTQ) mass spectrometers using purified helium as the buffer gas, showed two unexpected peaks at m/z 312 and 295. This enigmatic m/z 312 ion, which bears a mass-to-charge ratio higher than that of the precursor ion, represented an addition of molecular oxygen (O₂) to the precursor ion. The exceptional affinity of the m/z 280 radical cation towards oxygen was deployed to develop a method to determine the oxygen content in collision gases. Figure

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Determination of Free Fatty Acids in Tibet Folk Medicine Potentilla anserina L. Using a New Labeling Reagent by LC with Fluorescence Detection and Identification with Online Atmospheric Chemical Ionization-MS Identification

A sensitive method for the determination of free fatty acids using 1,2-benzo-carbazole-9-ethyl-p-toluenesulfonate (BCETS) as tagging reagent with fluorescence detection has been developed. BCETS could easily and quickly label fatty acids in the presence of the K₂CO₃ catalyst at 80 °C for 30 min in N,N-dimethylformamide solvent. In this study, fatty acids from the extracted Potentilla anserina L. plant sample were sensitively determined. The corresponding derivatives were separated on a reversed-phase Eclipse XDB-C₈ column by LC in conjunction with gradient elution. The identification was carried out by post-column APCI-MS in positive-ion detection mode. BCETS-fatty acid derivatives gave an intense molecular ion peak at m/z [M+H]⁺, the collision-induced dissociation spectra of m/z [M+H]⁺ produced the specific fragment ions at m/z [M′+CH₂CH₂]⁺, m/z 216.6 and m/z [MH?H₂O]⁺ (here, M′: corresponding molecular mass of the fatty acids). The fluorescence excitation and emission wavelengths of the derivatives were at λ _ex 279 nm and λ _em 380 nm, respectively. Linear correlation coefficients for all fatty acid derivatives are more than 0.9994. Detection limits, at a signal-to-noise ratio of 3:1, are 10.79–34.19 fmol for the labeled fatty acids.     

A comparative study of the antibacterial mechanisms of silver ion and silver nanoparticles by Fourier transform infrared spectroscopy

In this study, we performed the first comparative study of the antibacterial mechanisms of silver ion (Ag⁺) and silver nanoparticles (AgNPs) on Escherichia coli (E. coli) using Fourier transform infrared (FTIR) spectroscopy. Through a thorough analysis of the FTIR spectra of E. coli after silver treatment in the spectral regions corresponding to thiol group, protein, lipopolysaccharide (LPS), and DNA, we were able to reveal a multifaceted antibacterial mechanism of silver at the molecular level for both Ag⁺ and AgNPs. Features of such mechanism include: (1) silver complexes with thiol group; (2) silver induces protein misfolding; (3) silver causes loss of LPS from bacterial membrane; (4) silver changes the overall conformation of DNA. Despite the similarities between Ag⁺ and AgNPs with respect to their antibacterial mechanisms, we further revealed that Ag⁺ and AgNPs display quite different kinetics for silver-thiol complexation and loss of LPS, with Ag⁺ displaying fast kinetics and AgNPs displaying slow kinetics. At last, we proposed a hypothesis to interpret the observed different behaviors between Ag⁺ and AgNPs when interacting with E. coli.     

In Vitro and In Silico Evaluation of Cholinesterase Inhibition by Alkaloids Obtained from Branches of Abuta panurensis Eichler

Alkaloids are natural products known as ethnobotanicals that have attracted increasing attention due to a wide range of their pharmacological properties. In this study, cholinesterase inhibitors were obtained from branches of Abuta panurensis Eichler (Menispermaceae), an endemic species from the Amazonian rainforest. Five alkaloids were isolated, and their structure was elucidated by a combination of 1D and 2D ¹H and ¹³C NMR spectroscopy, HPLC-MS, and high-resolution MS: Lindoldhamine isomer m/z 569.2674 (1), stepharine m/z 298.1461 (2), palmatine m/z 352.1616 (3), 5-N-methylmaytenine m/z 420.2669 (4) and the N-trans-feruloyltyramine m/z 314.1404 (5). The compounds 1, 3, and 5 were isolated from A. panurensis for the first time. Interaction of the above-mentioned alkaloids with acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes was investigated in silico by molecular docking and molecular dynamics. The molecules under investigation were able to bind effectively with the active sites of the AChE and BChE enzymes. The compounds 1–4 demonstrated in vitro an inhibitory effect on acetylcholinesterase with IC₅₀ values in the range of 19.55 µM to 61.24 µM. The data obtained in silico corroborate the results of AChE enzyme inhibition.     

Substitution of Co in YBa2Fe3O8

The accommodation of Co in the oxygen-saturated solid-solution phase YBa₂(Fe_1−zCo_z)₃O_8+w has been investigated by powder X-ray and neutron diffraction techniques, as well as by Mössbauer spectroscopy. Of the nominal composition range 0.00?z?1.00 tested, the solid-solution limit under syntheses at 950°C in is z=0.47(5). No symmetry change in the nuclear and magnetic structures is seen as a consequence of the Co substitution, and the Co atoms are distributed evenly over the two sites that are square-pyramidally and octahedrally coordinated for w=0. The oxygen-saturated samples maintain their oxygen content roughly constant throughout the homogeneity range, showing that Co³⁺ replaces Fe³⁺. Despite the nearly constant value of w, Mössbauer spectroscopy shows that the amount of tetravalent Fe slightly increases with increasing z, and this allows Co to adopt valence close to 3.00 to a good approximation. The magnitude of the antiferromagnetic moment (located in the a,b plane) decreases with z in accordance with the high-spin states of the majority Fe³⁺ and Co³⁺ ions. Bond-valence analyses are performed to illustrate how the structural network becomes increasingly frustrated as a result of the substitution of Fe³⁺ by the smaller Co³⁺ ion. A contrast is pointed out with the substitution of cobalt in YBa₂Cu₃O₇ where it is a larger Co²⁺ ion that replaces smaller Cu²⁺.     

Effect of ion-molecule collisions in the vacuum chamber of an electrospray time-of-flight mass spectrometer on mass spectra of proteins

Electrospray ionization spectra of positive multiply charged ions of several proteins with molecular weight from 8565 to 339,100 u were recorded at different pressures of residual gas in the vacuum chamber of an electrospray time-of-flight mass spectrometer. The pressure was varied in the range (0.2 to 5) × 10^?6 torr. The effect of pressure was found to be significant even for the lightest protein investigated (ubiquitin), which resulted in a decrease of both sensitivity and resolution. Investigations of the arrival-time distributions and the energy distributions of ions showed that collision-induced dissociation (CID) of the protein ions in the drift region is the main process responsible for the effect. Several CID cross sections of proteins were estimated from a series of mass spectra recorded at different pressures in the reflecting mode: 1150 Ų for cytochrome c (averaged over charge states z = 14–18), 800 Ų for lysozyme (z = 8–10), 1840 Ų for apomyoglobin (z = 12–25), 800 Ų for holomyoglobin (z = 8), and 2500 Ų for carbonic anhydrase II (z = 22–35). Several experiments with large proteins in their native conformations and low charge states (m/z 0,000) demonstrate that these ions are less sensitive to high residual gas pressure.     

Diffusion coefficients of ions through ion excange membrane in Donnan dialysis using ions of different valence

Donnan dialysis with an ion exchange membrane was investigated for ions of different valence. The effective diffusion coefficients (D_e) of various kinds of ions in the membrane were obtained by fitting of the equation derived from the Nernst–Planck equation to three or more sets of experimental data for Donnan dialysis. It became apparent that the value of D_e/D_s of monovalent ions (e.g., K⁺ or Na⁺ ions) at z_A=1 and z_B=2 (feed ions are monovalent ones and driving ions are bivalent ones) remained constant at ca. 1/210 and that of bivalent ions (e.g., Ca²⁺, Cu²⁺, or Mg²⁺ ions) remained constant at ca. 1/526 where D_s denotes the diffusion coefficient of ions at infinite dilution in water calculated from the Nernst–Einstein equation, and z_A and z_B represent the valences of the feed and driving ions, respectively. D_e/D_s of monovalent ions (e.g., H⁺, K⁺, or Na⁺ ions) at z_A=2 and z_B=1 (feed ions are bivalent ones and driving ions are monovalent ones) was constant at ca. 1/23.3 and that of bivalent ions remained constant at ca. 1/58.4. It was proved that D_e/D using D_e at z_A=1 and z_B=2 was constant at 1/3.0 and that at z_A=2 and z_B=1 remained constant at 3.0 where D represents the diffusion coefficient of ions in the membrane at z_A=z_B (the valences of both feed and driving ions are equal). Therefore, it was found that a large flux of ions could be obtained using the monovalent driving ions in Donnan dialysis. On the other hand, the small flux can be obtained using bi- or higher-valent driving ions.     

Spin-orbit perturbation of the anion states by a heavy cation in NaNO2:Ag+

Optical and ODMR studies of NaNO₂: Ag⁺ crystals at T < 4.2 K have shown very selective spin-orbit perturbations on the properties of the nitrite triplet state T₁, by the heavy cation dopant. The perturbed T₁ — S₀ transition shows mainly z-axis polarization associated with the τ_y spin state (z- and y-axes in-plane with the z-axis bisecting the ONO angle). The fine structure splitting constants for the perturbed T₁ state are D = -3Y/2 = ± 15.508 GHz and E = (Z - X)/2 = 3 .643 GHz.     

Zur Elektronenstruktur metallorganischer Komplexe der φ-Elemente—XXVI. Einkristall-optische und magnetooptische Untersuchungen am Essigsäure-n-butylester Addukt des Grundkörpers Tris-(η5-cyclopentadienyl)—praseodym(III)

By comparing the absorption spectrum of an oriented single crystal of the n-butylacetate adduct derived from tris (η⁵-cyclopentadienyl)-praseodymium(III) with the corresponding absorption spectrum run as pellet or solution, the excited terminal crystal field states of A₁ and E symmetry, respectively, could be assigned. Additionally, the magnetic circular dichroism spectrum of this complex was recorded in the range 430–2070 nm. From the selection rules for magnetic circular dichroism spectroscopy the dominant 1 ± J_z > values in the eigenvectors of some excited E states could be determined. The experimental results agree with the predictions of a previous crystal field calculation.     

Parametric investigation of the isotope shift in odd configurations of Ne i

Isotope shift measurements were performed on 33 transitions of Ne i by means of optogalvanic and intermodulated optogalvanic spectroscopy as well as saturation absorption spectroscopy. Using a large number of line isotope shift values obtained from both literature and our measurements, the level isotope shifts were calculated with improved concistency. Fine structure calculations were performed in odd configurations in order to obtain isotope shift parameters by means of the parametric method, 2p ⁵ 3s: g1 = -1077.5(7), z _2p = 15.3(3), 2p⁵5 s: g ₁ = -104(26), z _2p = 14(6), 2p ²4d: g ₁ = -42(6), z _2p = 17(3).     

Mass spectrometry of metal compounds. III. Electron-impact-induced mass spectrometric studies of bis(acetylacetonato)dioxomolybdenum(VI), MoO2(C5H7O2)2, and tetrakis(acetylacetonato)dioxo-μ-oxodimolybdenum(V), Mo2O3(C5H7O2)4

Electron-impact-induced mass spectra of MoO₂(C₅H₇O₂)₂, 1, and Mo₂O₃(C₅H₇O₂)₄, 2, recorded at an ion-source temperature of 100°C show the molecular ion signals at m/z 328 and at m/z 636, respectively, indicating that they do not undergo association in the vapour state. The parent ion of 1, unlike bis(acetylacetonato)metalates of the first-row transition metals, loses (CH₂CO followed by C₃H₅O to produce [MoO₂(C₅H₇O₂)]⁺ at m/z 229, the base peak, which ultimately fragments to [MoO₂]⁺. The molecular ion of 2, [Mo₂O₃(C₅H₇O₂)₄]⁺, undergoes fragmentation following two different, but equally probable, pathways with one involving the loss of C₅H₇O₂ and C₅H₇O groups producing the ion [Mo₂O₄(C₅H₇O₂)₂]⁺, and the other involving the formation of the ion [MoO(acac)₂]⁺ directly from the parent ion. The signal at m/z 312 owing to the ion [MoO(C₅H₇O₂)₂]⁺ constitutes the base peak in the spectrum of 2. Metastable transitions were studied, and the most probable fragmentation schemes for the compounds 1 and 2 are suggested. There is evidence for CH₃ shift from the ligand to the oxygen atoms bound to the metal centres or to form metal-carbon bonds.     

Synthesis, structural characterization and Li ion conductivity of a new vanado-molybdate phase, LiMg3VMo2O12

A new vanado-molybdate LiMg₃VMo₂O₁₂ has been synthesized, the crystal structure determined an ionic conductivity measured. The solid solution Li_2−zMg_2+zV_zMo_3−zO₁₂ was investigated and the structures of the z=0.5 and 1.0 compositions were refined by Rietveld analysis of powder X-ray (XRD) and powder neutron diffraction (ND) data. The structures were refined in the orthorhombic space group Pnma with a∼5.10, b∼10.4 and c∼17.6 Å, and are isostructural with the previously reported double molybdates Li₂M₂(MoO₄)₃ (M=M²⁺, z=0). The structures comprise of two unique (Li/Mg)O₆ octahedra, (Li/Mg)O₆ trigonal prisms and two unique (Mo/V)O₄ tetrahedra. A well-defined 1:3 ratio of Li⁺:Mg²⁺ is observed in octahedral chains for LiMg₃VMo₂O₁₂. Li⁺ preferentially occupies trigonal prisms and Mg²⁺ favours octahedral sheets. Excess V⁵⁺ adjacent to the octahedral sheets may indicate short-range order. Ionic conductivity measured by impedance spectroscopy (IS) and differential scanning calorimetry (DSC) measurements show the presence of a phase transition, at 500-600 °C, depending on x. A decrease in activation energy for Li⁺ ion conductivity occurs at the phase transition and the high temperature structure is a good Li⁺ ion conductor, with σ=1×10⁻³-4×10⁻² S cm⁻¹ and E_a=0.6 to 0.8 eV.     

Unimolecular decomposition of energy-selected anisole ions. Breakdown graph and metastable decay rates

The fragmentation behavior of the anisole ion (C₆H₅OCH^+·₃) was examined using threshold photoelectron-photoion coincident (TPEPICO) mass spectrometry. Four major fragments are observed in the ion time-of-flight spectra at photon energies less than 14 eV: C₆H₅O⁺ (m/z 93), C₆H⁺₇ (m/z 79), C₆H⁺₆ (m/z 78), and C₅H⁺₅ (m/z 65). Rate constants for the production of the ion m/z 78 near threshold were found to agree well with those calculated on the basis of RRKM theory. Most of the excess energy at threshold for this process is a result of the kinetic shift.     

NMR evidence of LiF coating rather than fluorine substitution in Li(Ni0.425Mn0.425Co0.15)O2

A series of “Li_1+z/2(Ni_0.425Mn_0.425Co_0.15)_1−z/2O_2−zF_z” materials was prepared by a coprecipitation route and their structure was characterized using X-ray diffraction (XRD), as well as ⁷Li and ¹⁹F Magic Angle Spinning (MAS) NMR spectroscopy. Two hypotheses were considered: (i) formation of layered oxyfluoride materials and (ii) formation of a mixture between the layered material and LiF. Structural parameters were refined by the Rietveld method, using XRD diffraction data. The refinement results did not allow us to choose between these two hypotheses: no significant change in crystallinity and structural parameters was observed irrespective of the fluorine ratio. ⁷Li and ¹⁹F MAS NMR analyses showed signals with isotropic positions characteristic of LiF, but envelopes characteristic of very strong dipolar interactions with the electron spins of the material, demonstrating that LiF was not incorporated into the layered oxide structure but was instead present as a coating.     

Zero-point average structures of acetyl chloride and acetyl bromide

The zero-point average structures of acetyl chloride and acetyl bromide have been determined by the combined use of their moments of inertia and average distances, obtained by means of microwave spectroscopy and electron diffraction. The r_z parameters determined are as follows: r_z(CO) = 1.185 ± 0.003 Å, r_z(C-Cl) = 1.796 ± 0.002 Å, r_z(C-C) = 1.505 ± 0.003 Å, r_z(C-H) = 1.092 ± 0.005 Å, φ_z(OCCl) = 121.2 ± 0.6°, φ_z(CCCl) = 111.6 ± 0.6°, φ_z(HCH) = 108.8 ± 0.8° and tilt(CH3) = 1.3 ± 1.0°, for chloride; r_z(CO) = 1.181 ± 0.003 Å, r_z(C-Br) = 1.974 ± 0.003 Å, r_z(C-C) = 1.516 ± 0.003 Å, φ_z(OCBr) = 122.3 ± 1.5°, φ_z(CCBr) = 111.0 ± 1.5°, φ_z(HCH) = 109.9 ± 1.1°, tilt(CH₃) = 1.9 ± 1.0°, for bromide. The barriers V₃ to internal rotation have been revised to 1260 and 1256 cal mol⁻¹ for the chloride and bromide, respectively.     

A sensitive fluorescence reagent for the determination of aldehydes from alcoholic beverage using high-performance liquid chromatography with fluorescence detection and mass spectrometric identification

A pre-column derivatization method for the sensitive determination of aldehydes using the tagging reagent 2-[2-(7H-dibenzo[a,g] carbazol-7-yl)-ethoxy] ethyl carbonylhydrazine (DBCEEC) followed by high-performance liquid chromatography with fluorescence detection and APCI-MS identification has been developed. The chromophore of fluoren-9-methoxy-carbonylhydrazine (Fmoc-hydrazine) reagent was replaced by 2-[2-(7H-dibenzo[a,g] carbazol-7-yl)-ethoxy] ethyl functional group, which resulted in a sensitive fluorescence tagging reagent DBCEEC. DBCEEC could easily and quickly labeled aldehydes. The maximum excitation (300 nm) and emission (400 nm) wavelengths did not essentially change for all the aldehyde derivatives. Derivatives were sufficiently stable to be efficiently analyzed by high-performance liquid chromatography. The derivatives showed an intense protonated molecular ion corresponding m/z [M + (CH₂)_n]⁺ in positive-ion mode (M: molecular weight of DBCEEC, n: corresponding aldehyde carbon atom numbers). The collision-induced dissociation of protonated molecular ion formed fragment ions at m/z 294.6, m/z 338.6 and m/z 356.5. Studies on derivatization demonstrated excellent derivative yields in the presence of trichloroacetic acid (TCA) catalyst. Maximal yields close to 100% were observed with a 10 to 15-fold molar reagent excess. Separation of the derivatized aldehydes had been optimized on ZORBAX Eclipse XDB-C₈ column with aqueous acetonitrile as mobile phase in conjunction with a binary gradient elution. Excellent linear responses were observed at the concentration range of 0.01-10 nmol mL⁻¹ with coefficients of >0.9991. Detection limits obtained by the analysis of a derivatized standard containing 0.01 nmol mL⁻¹ of each aldehyde, were from 0.2 to 1.78 nmol L⁻¹ (at a signal-to-noise ratio of 3).     

Hyperfine structure of the resonance lines of53Cr and lifetimes of some excited states of the Cr I spectrum

The hyperfine structure of the⁵³Cr resonance linesa ⁷ S ₃ ?z ⁷ P _2,3,4 has been investigated by means of laser saturation spectroscopy. By comparison of the experimental signal curves with theoretically computed spectra the hitherto unknown sign of the magnetic hyperfine coupling constant in thea ⁷ S ₃ ground state of⁵³Cr could be determined unambigiously to be negative. Further the signs of the hfs coupling constants in thez ⁷ P states — so far only evaluated by theoretical reasoning — could be confirmed. Additionally the lifetimes of the statesz ⁷ P,z ⁵ P,f ⁷ D,z ⁵ F,e ⁷ D ₅ andy ⁵ P ₃ in the Cr I spectrum have been determined from the fluorescence decay after pulsed laser excitation.