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101.
Inoue K Ikemura A Tsuruta Y Tsutsumiuchi K Hino T Oka H 《Biomedical chromatography : BMC》2012,26(2):137-141
We developed a high-throughput method based on on-line solid-phase extraction liquid chromatography tandem mass spectrometry (SPE-LC-MS/MS) to determine N-terminal thymosin-β fragment peptide (N-acetyl-seryl-aspartyl-lysyl-proline, Ac-SDKP) in human plasma samples. Quantification of Ac-SDKP was performed using direct injection for on-line SPE based on C(18), reversed-phase LC separation and stable isotope dilution electrospray ionization-MS/MS in multiple reaction-monitoring (MRM) mode. The Ac-SDKP-(13)C(6), (15)N(2) (m/z 496 → 137) was synthesized for the internal standard. The MRM ion for Ac-SDKP was m/z 488 → 129 (quantitative ion)/226. The limit of detection and lower limit of quantitation were 0.05 and 0.1 ng/mL in standard solution, respectively. Recovery values were 98.3-100.4% with inter-day (relative standard deviation, RSD, 0.4-14.1%) and intra-day (RSD, 0.8-19.7%) assays. This method was applied to the measurement of Ac-SDKP levels in plasma from hemodialyzed subjects. Concentrations were 0.59 ± 0.23 ng/mL (pre-hemodialyzed subjects, n = 9) and 0.44 ± 0.19 ng/mL (post-hemodialyzed subjects, n = 9). All plasma Ac-SDKP levels were decreased by dialysis. Thus, plasma Ac-SDKP was decreased through dialysis in chronic kidney disease. The findings in this study will be useful for the treatment of anemia in chronic kidney disease with dialysis. 相似文献
102.
A convenient method has been developed for the synthesis of diphenyl α-（dipropoxyphosphoramido）alkyl- phosphonates under mild conditions, namely the reaction of dipropyl phosphoramidate （1） with a para（un）substituted benzaldehyde or cyclicketone （2） and triphenyl phosphite （3） by a one-pot procedure with the aid of acetyl chloride. 相似文献
103.
Hansen PE Kamounah FS Hansen BK Spanget-Larsen J 《Magnetic resonance in chemistry : MRC》2007,45(2):106-117
Tautomerism in aromatic systems with oxygen substitutents is rare. This is investigated in 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene (1) and in 2,7-diacetyl-1,8-dihydroxy-3,6-dimethylnaphthalene (2). The tautomeric nature of 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene is supported by long-range hydrogen-hydrogen coupling between the OH-1 and the OH-8 and by the isotope effects on 13C caused by deuteration at the CH3C==O methyl group. Compound 2 participates in a degenerate equilibrium between two equivalent nonsymmetrical rotamers (2A and 2B), each having two intramolecular O...HO hydrogen bonds: one involving an acetyl oxygen and the neighboring hydroxyl group, and the other between the oxygen centers at positions 1 and 8. In addition, each rotamer is involved in a tautomeric equilibrium, with a structure having an OH-substituted exocyclic double bond (2AT or 2BT).DFT calculations for a large set of compounds highlight the factors controlling the unusual rotational and tautomeric behaviors. A very important factor seems to be the repulsive interaction between the O-1 and O-8 centers, which is modulated by formation of an OH-1...O-8 or OH-8...O1 hydrogen bond. Steric interactions, mesomeric release of electrons from the oxygen at position 8, and a strong OH...O...C hydrogen bond are other factors.Solid-state 13C NMR spectra of 2,7-diacetyl-1,8-dihydroxy-3,6-dimethylnaphthalene at different temperatures demonstrated no averaging in the solid, whereas partially deuterated 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene showed an isotope effect at C-1 of 1.5 ppm, indicating tautomerism in the solid state. 相似文献
104.
An expedient concise total synthesis of (+)‐7‐epigoniodiol, (?)‐8‐epigoniodiol, and (+)‐9‐deoxygoniopypyrone is accomplished. The key transformations include a catalytic hydroxylation and base‐mediated N‐(acetyl)oxazolidinone addition reactions, which could set the consecutive OH motif that is either syn,syn or syn,anti with high diastereoselectivity. Moreover, this approach envisioned to facilitate the synthesis of other representatives of the family with structural and stereochemical variation. 相似文献
105.
Heating of o-acetoxybenzoyl azides 6–10 in toluene leads to the Curtius reaction, which, when followed by closure of oxazolone ring with concomitant migration of acetyl group from oxygen to nitrogen, produces 3-acetoxybenz[d]oxazol-2(3H)-ones 11–15, which undergo hydrolysis with hot dilute hydrochloric acid to furnish benz[d]oxazol-2(3H)-ones 17–21. Thermal reaction of 2-hydroxy-5-nitrobenzoyl azide (22) in toluene finally yields a mixture of 5-nitrobenz[d]oxazol-2(3H)-one (20) and 5-nitrobenz[d]isoxazol-3(2H)-one (23). 相似文献
106.
The formation of acetyl phosphate (AcP), an energy‐rich phosphate compound, was studied through the reaction of 2,4‐dinitrophenyl acetate with H2PO solubilized with Kryptofix® 222 or as a tetra‐n‐butylammonium ((n‐C4H9)4N+) salt in organic media. The results indicated that the rate of the reaction in acetonitrile is strongly inhibited by the addition of water, suggesting that the water added to the medium preferentially solvates the H2PO anion, inhibiting its action as a nucleophile and allowing it to act as a general base catalyst, which leads to the hydrolysis of the ester. The utilization of various organic solvents in the acetyl transfer process demonstrated that the specific interaction of the solvent with water accelerates the process, by desolvation of H2PO, which can act as a nucleophile. Finally, a formation/transformation cycle of AcP was studied in a biphasic system (water/CH2Cl2) using Kryptofix® 222 and (n‐C4H9)4N+BF as both the carrier and solubilizing agent for KH2PO4. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
107.
Nighat Kausar Bruce D. Alexander Trevor J. Dines Robert Withnall Babur Z. Chowdhry 《Journal of Raman spectroscopy : JRS》2009,40(6):661-669
Experimental vibrational spectroscopic studies and density functional theory (DFT) calculations of the di‐amino acid peptide derivatives α‐ and β‐N‐acetyl‐L‐Asp‐L‐Glu have been undertaken. Raman and infrared spectra have been recorded for samples in the solid state. DFT simulations were conducted using the B3‐LYP correlation functional and the cc‐pVDZ basis set to determine energy minimized/geometry optimized structures (based on a single isolated molecule in the gaseous state). Normal coordinate calculations have provided vibrational assignments for fundamental modes, including their potential energy distributions. Significant differences are observed between α‐ and β‐N‐acetyl‐L‐Asp‐L‐Glu both in the computed structures and in the vibrational spectra. The combination of experimental and calculated spectra provide an insight into the structural and vibrational spectroscopic properties of di‐amino acid peptide derivatives. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
108.
Introduction Taxol exhibits a unique mode of action on microtuble proteins which is responsible for the spindle formation during cell division.In contrast to other spindle forma-tion inhibitors such as vinblastine or colchicine,both of which prevent the t… 相似文献
109.
《化学分析计量》2020,(5)
Abstract：A gas chromatography-mass spectrometry (GC-MS) method was developed for the determination of cyclohexanone and acetyl tributyl citrate migration from disposal syringes and accessories. Two contrast agents were selected and infused through disposal syringes and accessories by simulating clinical use, and then extracted with n-hexane. GC-MS method was adopted for the quantitative analysis of cyclohexanone and acetyl tributyl citrate. The results showed that the linearity of cyclohexanone and acetyl tributyl citrate was good respectively in the range of 0.151-0.906 μg/mL and 0.047 5-0.475 0 μg/mL with the corelation coefficient not less than 0.999 4. The relative standard deviations of the detection results were 1.0%-3.6%(n=6), and the recoveries were 92.3%-103.9% and 67.6%-89.7%. The method is simple, rapid, sensitive, reliable and it is suitable for the determination of cyclohexanone and acetyl tributyl citrate released from disposal syringes and accessories. 相似文献
110.
用密度泛函方法的B3LYP在6-31＋g（d，p）基组水平上，研究了底物对-氨基苯甲酸与芳基胺-N-乙酰基转移酶之间的乙酰化反应．该反应共有两种可能的反应机理：协同反应和分步反应．计算结果表明，协同反应机制在竞争中占优势，是势能面上的最低能量反应通道． 相似文献