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The redox nature of the non-oxido vanadium sulfur center is associated with several biological systems such as vanadium nitrogenase, the reduction of vanadium ion in ascidians, and the function of amavadin, which is a vanadium(IV)...
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The redox nature of the non-oxido vanadium sulfur center is associated with several biological systems such as vanadium nitrogenase, the reduction of vanadium ion in ascidians, and the function of amavadin, which is a vanadium(IV) natural product contained in Amanita mushrooms. But the related chemistry is less explored and understood compared to oxido vanadium species due to the oxophilic character of high valent vanadium ions. Herein, we present a class of non-oxido, vanadium thiolate complexes, [V-III(PS2 '' S-H)(2)](-) (1) (PS2 '' S-H = [P(C6H3-3-Me3Si-2-S)(2)(C6H3-3Me(3)Si-2-SH)](2-)), [V-IV(PS3 '') (PS2 '' S-H)](-) (2) (PS3 '' = [P(C6H3-3Me(3)Si-2-S)(3)](3-)), [V(PS3 '')(2)](-) (3), [V(PS3 '')(PS2 '' S-H)] (4), and [V-IV(PS3*)(2)](2-) (5a) (PS3* = [P(C6H3-3-Ph-2-S)(3)](3-)), and study their interconversion through the redox and acid-base reactions. Complex 1 consists of a six-coordinate octahedral vanadium center; complexes 2 and 4 are seven-coordinate with distorted capped trigonal prismatic geometry. Vanadium centers of 3 and 5a are both eight-coordinate; the former adopts ideal dodecahedral geometry, but the latter is better viewed as a distorted square antiprism. Complex 1 is oxidized to complex 2 and then to complex 3 with dioxygen. Each one-electron oxidation process is accompanied by the deprotonation of unbound thiol to bound thiolate. Complex 3 is also produced from complex 2 through stepwise addition of Fe(Cp)(2)(+)/n-BuLi, or in the reverse order. The formation of 2 from 3 is achieved in the order of adding Co(Cp)(2) and acid or, as with the previous complex, inversely. Notably, the reduction of complex 2 to complex 1 accompanying the protonation of bound thiolate to unbound thiol only occurs with the presence of both Co(Cp)(2) and acid, indicating a cooperative effect between the metal-centered reduction and bound thiolate protonatiori. The conversions among these complexes are observed with ESI-MS and,UV-vis-NIR spectroscopies. The work demonstrat
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Abundant blood proteins adducted by active electrophiles are excellent markers to predict the risk of electrophile-induced toxicity. However, detecting endogenously adducted proteins by bottom-up selective (or parallel) reaction m...
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Abundant blood proteins adducted by active electrophiles are excellent markers to predict the risk of electrophile-induced toxicity. However, detecting endogenously adducted proteins by bottom-up selective (or parallel) reaction monitoring (SRM/PRM) is challenging because of the high variability in sample preparation and detection as well as low adduction levels. Here, we reported a new approach in developing PRM methods by combining intact protein measurement with standard additions to target optimal conditions for detecting catechol estrogens (CEs)-adducted human serum albumin (HSA). Blood serum was added with multiple amounts of CEs to obtain serum standards. Intact protein measurement revealed two linear ranges of adduction levels (adducted-CE/HSA): 0.34-0.42 (R-2 > 0.94) and 0.81-8.54 (R-2 > 0.96) against the amount of added CEs, respectively. Six adduction sites were identified by trypsin (K20, C34, K73, K281, H338, K378) or chymotrypsin (K20, C34, K378) digestion. PRM methods targeting all adducted/nonadducted peptide pairs based on chymotrypsin or trypsin digestion were developed, and the data were compared with those obtained by intact protein measurement. Correlation plots indicated that chymotrypsin-PRM leads to poor sensitivity and largely underestimated protein adduction levels. Trypsin-PRM leads to sensitive and highly correlated (R-2 > 0.91) protein adduction levels with a detection limit below the endogenous level and relative standard deviation <25%. As a proof of concept, clinical serum samples were examined by trypsin-PRM, and a slightly higher adduction level was observed for the obesity group when compared with the healthy group. This is the first report on determining adduction levels of blood proteins for long-term exposure to CEs. The standard addition approach can be generally applied to protein adductomics with resolvable mass increments by intact protein measurement to accelerate the development of bottom-up methods close to the inherent limit.
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Adsorption and reactions of 3-bromopyridine and 2-bromopyridine on Cu(100) and O/Cu(100) have been investigated, attempting to explore the chemical processes by identifying a variety of possible reaction intermediates and products...
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Adsorption and reactions of 3-bromopyridine and 2-bromopyridine on Cu(100) and O/Cu(100) have been investigated, attempting to explore the chemical processes by identifying a variety of possible reaction intermediates and products, such as bipyridine, pyridyne, pyridine, pyridine oxide, hydroxypyridine, pyridone, and so forth. They can be generated from the Ullmann reaction, dehydrogenation, hydrogenation, hydroxylation, and oxidation of pyridyl groups on the surfaces. Temperature-programmed reaction/desorption, reflection-absorption infrared spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations have been employed for this research. At a monolayer coverage of 3-bromopyridine on Cu(100), a perpendicular 3-pyridyl is generated on the surface below 300 K because of the C-Br bond scission. This surface species undergoes loss of hydrogen, hydrogenation, and ring rupture at similar to 450 K. The first two processes result in the pyridine formation. The dissociated fragments continue to react to form H-2, HCN, and (CN)(2) at higher temperatures. The relative amounts of the products of pyridine, H-2, HCN, and (CN)(2) are dependent on the coverage of 3-pyridyl. In the presence of surface oxygen atoms (O-(ad)), dissociation of 3-bromopyridine also generates 3-pyridyl first. However, the pyridine formation from this intermediate is terminated, with decreased H2, HCN, and (CN)(2). Additional products of H2O, CO, CO2, and HNCO are generated. For 2- bromopyridine (1.0 L) on Cu(100), at a coverage slightly higher than a monolayer, a perpendicular 2-pyridyl is generated below 300 K, and its decomposition generates pyridine (similar to 525 K), together with H-2, HCN, and (CN)(2) at higher temperatures. At a large exposure of 10.0 L of 2-bromopyridine, additional pyridine is generated at 650 K, which is suggested to be originated from an electronically/structurally strongly perturbed CsNH4 intermediate. On O/Cu(100), no 2-pyridyl intermediate is measured from the primary 2-bromopyridine decomposition; however, 2-oxypyridine is formed instead. This intermediate can be produced from nucleophilic attack on the C-2 atom of 2-bromopyridine by O-(ad) and/or from recombination of 2-pyridyl and O-(ad). The 2-oxypyridine further reacts to form H2O, HCN, CO, CO2, HCNO, and (CN)(2).
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Catechol estrogens (CEs) are metabolic electrophiles that actively undergo covalent interaction with cellular proteins, influencing molecular function. There is no feasible method to identify their binders in a living system. Here...
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Catechol estrogens (CEs) are metabolic electrophiles that actively undergo covalent interaction with cellular proteins, influencing molecular function. There is no feasible method to identify their binders in a living system. Herein, we developed a click chemistry-based approach using ethinylestradiol (EE2) as the precursor probe coupled with quantitative proteomics to identify protein targets of CEs and classify their binding strengths. Using in situ metabolic conversion and click reaction in liver microsomes, CEs-protein complex was captured by the probe, digested by trypsin, stable isotope labeled via reductive amination, and analyzed by liquid chromatography mass spectrometry (LC MS). A total of 334 liver proteins were repeatedly identified (n >= 2); 274 identified proteins were classified as strong binders based on precursor mass mapping. The binding strength was further scaled by D/H ratio (activity probe/solvent): 259 strong binders had D/H > 5.25; 46 weak binders had 5.25 > D/H > 1; 5 nonspecific binders (keratins) had D/H < 1. These results were confirmed using spiked covalent control (strong binder) and noncovalent control (weak binder), as well as in vitro testing of cytochrome c (D/H = 5.9), which showed covalent conjugation with CEs. Many identified strong binders, such as glutathione transferase, catechol-O-methyl transferase, superoxide dismutase, catalase, glutathione peroxidase, and cytochrome c, are involved in cellular redox processes or detoxification activities. CE conjugation was shown to suppress the superoxide oxidase activity of cytochrome c, suggesting that CEs modification may alter the redox action of cellular proteins. Due to structural similarity and inert alkyne group, EE2 probe is very likely to capture protein targets of CEs in general. Thus, this strategy can be adopted to explore the biological impact of CEs modification in living systems.
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1,3-Thiazole is found to be nearly perpendicularly adsorbed on Cu(100), with the N atom attaching to an atop site and an adsorption energy of similar to 19.5 kcal.mol(-1). The N-C-S moiety of the adsorbed 1,3-thiazole has a larger...
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1,3-Thiazole is found to be nearly perpendicularly adsorbed on Cu(100), with the N atom attaching to an atop site and an adsorption energy of similar to 19.5 kcal.mol(-1). The N-C-S moiety of the adsorbed 1,3-thiazole has a larger change in bond length as compared to a free 1,3-thiazole molecule. The adsorbed 1,3-thiazole can decompose below 200 K, forming atomic S and -CHCHNCH-. A small amount of R-S- (R: CHCHNCH) is detected on the surface at 200 K. Complete desulfurization of the 1,3-thiazole occurs at 400 K. Further reaction of the -CHCHNCH- produces H-2 and HCN at higher temperatures. In the presence of adsorbed oxygen atoms(O/Cu(100)), new disulfide intermediates (R-S-S-R, R: CHCHNCH) from the thiazole reaction are measured at 300 K and can further decompose into atomic S and -CHCHNCH- at 400 K. In addition, other surface species of -NCO and >C=C=O are also observed at 500 K. These species eventually react to generate H2O, CO, CO2, and N-2. Further calculations indicate that the S-CHN bond of 1,3-thiazole would break preferentially, as compared to the S-CHCH bond, in the decomposition process on Cu(100).
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S-doped rutile has been prepared for the first time by hydrothermal reaction of TiS2 in hydrochloric acid at a low temperature (180 degrees C), with the S atoms in three states of Ti S Ti, Ti S-O and SO4. TiS2 in nitric acid can a...
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S-doped rutile has been prepared for the first time by hydrothermal reaction of TiS2 in hydrochloric acid at a low temperature (180 degrees C), with the S atoms in three states of Ti S Ti, Ti S-O and SO4. TiS2 in nitric acid can also be transformed into TiO2, but with mixed phases of anatase and rutile, containing nitrogen atoms at interstitial sites in the form of Ti-O-N or Ti-N-O. The S-TiO2 catalyst shows a better visible-light reactivity toward adsorbed methylene blue (MB) photodegradation and hydroxylation of terephthalic acid with respect to the N-TiO2. The possible reasons leading to the high photoactivity of the S TiO2 are discussed in terms of the incorporated sulfur states. (C) 2015 Elsevier B.V. All rights reserved.
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Stimulated emission pumping with fluorescence depletion spectroscopy is used to determine the NaD X-1 Sigma(+) ground-state dissociation energy and its isotopic shift. A total of 230 rovibrational levels in the range 9 展开
Stimulated emission pumping with fluorescence depletion spectroscopy is used to determine the NaD X-1 Sigma(+) ground-state dissociation energy and its isotopic shift. A total of 230 rovibrational levels in the range 9 收起
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The 2(1)Pi state of NaH has been observed up to the last bound vibrational level using pulsed optical-optical double resonance fluorescence depletion spectroscopy. A total of 20 rovibrational energy levels (upsilon = 2-4 and J = 1...
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The 2(1)Pi state of NaH has been observed up to the last bound vibrational level using pulsed optical-optical double resonance fluorescence depletion spectroscopy. A total of 20 rovibrational energy levels (upsilon = 2-4 and J = 1-9) were assigned to this electronic state by means of comparing the successive rovibrational spectra to the eigenvalues of the ab initio potential energy curve. The decrease of background fluorescence near the atomic asymptotic limit Na(3d) + H(1s) is an indication of reaching the dissociation limit of the NaH 2(1)Pi state. Unobserved rovibrational levels (v = 0 and 1) are due to poor Franck-Condon overlap of 2(1)Pi <- A(1)Sigma(+) transition within the accessible rovibrational levels of intermediate A(1)Sigma(+) state of this work.
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X ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, temperature-programmed reaction/desorption, and density functional theory calculations have been performed to investigate the reaction mechanisms and b...
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X ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, temperature-programmed reaction/desorption, and density functional theory calculations have been performed to investigate the reaction mechanisms and bonding structures of 3- and 2-bromopropanoic acids on Cu(100) and oxygen-precovered Cu(100). On Cu(100), the bond dissociation of C-Br and O-H in BrCH2CH2COOH is accelerated, occurring at 110 K, as compared to the monofunctional molecules. CH2CH2COOH, CH2CH2COO, and CH3CH2COO from the BrCH2CH2COOH reaction coexist on Cu(100) at 180 K. The CH2CH2COOH is not detected at 250 K, and CH3CH2COO predominates at 320 K. The CH2CH2COO is strongly bonded to the surface via the COO and terminal CH2 groups. In the presence of oxygen atoms on Cu(100), the C-Br scission is suppressed and BrCH2CH2COO is found to be predominant at 150 K. CH2CH2COO begins to form at 200 K and further reacts to produce CH3CH2COO and CH2=CHCOO at 320 K through disproportionation or sequential H loss at (CH2)-C-2 and hydrogenation at (CH2)-C-3. The reaction of CH3CHBrCOOH on Cu(100) also generates CH3CH2COO at 300 K via CH3CHCOOH and CH3CHCOO. The latter species could attach to the surface via the CHCOO or COO group. On 0/Cu(100), dissociation of CH3CHBrCOOH forms CH3CHCOO between 200 and 400 K. CH3CHCOO on O/Cu(100) dehydrogenates, at 450 K, into CH2=CHCOO. A halogen (Cl and Br) effect is observed in the adsorption structure and reaction path of CH3CHCOO on O/Cu(100).
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We have synthesized a series of lanthanide-based metal-organic solids and characterized them through structural, magnetic and luminescence analyses. The nine compounds in the series NH4[Ln(SO4)(H2O)(C2O4)] [Ln = Ce, Nd, Eu, Gd (x2...
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We have synthesized a series of lanthanide-based metal-organic solids and characterized them through structural, magnetic and luminescence analyses. The nine compounds in the series NH4[Ln(SO4)(H2O)(C2O4)] [Ln = Ce, Nd, Eu, Gd (x2), Tb, Dy, Er, Yb] belong to four new three-dimensional (3D) structural groups, which we label CKMOF-4a, -4b, -5a, and -5b. The CKMOF-4a (Ce center dot 1) and -4b (Gd center dot 5, Tb center dot 6, Dy center dot 7, Er center dot 8, Yb center dot 9) structures feature [Ln(2)(SO4)(2)(H2O)(2)](2+) units and C2O42- ligands having the same symmetry operations, but their SO42- anions feature different connective modes. These units are extended into one-dimensional ribbons fused together by oxalate ligands to form the two 3D open frameworks. The structures of CKMOF-5a (Nd center dot 2) and -5b (Eu center dot 3, Gd center dot 4) comprise networks of c-glide-arranged [Ln(2)(SO4)(2)(H2O)(2)](2+) units, in which the oxalate ligands are encapsulated within eight-membered rings. The networks are supported by distinct sites of oxalate ligands to form the two types of 3D open frameworks, the structural topologies of which are distinguished by the versatile connective modes of the SO42- anions. The polymeric phases CKMOF-4b and -5b exist in the Gd analogues. For the Dy analogues, varying the size of the cation used as the template led to the selective precipitation of each of these two phases. The layer structure of [Gd(SO4)(H2O)(2)(CH3CO2)] (Gd center dot 10), labelled CKMOF-6, assembled from [Gd-2(SO4)(2)(H2O)(4)](2+) units and acetate ligands; the geometries of the [Gd2O2] rhombic units may induce ferromagnetic coupling at low temperature. Eu center dot 3 and Tb center dot 6 were luminescent, displaying red and green emissions, respectively.
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