Separation and identification of trinucleotide–melphalan adducts from enzymatically digested DNA using HPLC–ESI–MS

Melphalan is a bifunctional alkylating agent that covalently binds to the nucleophilic sites present in DNA. In this study we investigated oligonucleotides prepared enzymatically from DNA modified with melphalan. Calf thymus DNA was incubated in-vitro with melphalan and the resulting modifications were enzymatically cleaved by means of benzonase and nuclease S1. Efficient sample preconcentration was achieved by solid-phase extraction, in which phenyl phase cartridges resulted in better recovery of the modified species than C₁₈. The applied enzymatic digestion time resulted in production of trinucleotide adducts which were efficiently separated and detected by use of reversed-phase HPLC coupled to an ion-trap mass spectrometer with electrospray ionization. It was assumed that melphalan could act as both a monofunctional and bifunctional alkylating agent. Mono-alkylated adducts were much more abundant, however, and the alkylation site was located on the nucleobases. On the other hand, we unequivocally identified cross-link formation in DNA, even though at low abundance and only a few adduct types were detected. Figure Different Alkylation reactions of Melphalan with DNA     

Preliminary Characterization of the Composition and Phenolic Fragmentation of Olive Byproducts by Gas Chromatography–Mass Spectrometry and High-Performance Liquid Chromatography–Tandem Mass Spectrometry

Olive waste is a potential resource due to its rich variety of biologically active compounds. To investigate chemical components of olive waste, the selected samples were extracted using ultrasound assisted enzyme hydrolysis and petroleum ether, ethyl acetate and n-butyl alcohol were used to obtain a series of solvent extracts. Gas chromatography–mass spectrometry analysis showed hydrocarbons, esters, acids, alcohols, and ketones present in the extracts. Some fatty acids were considered to be predominant; it is noteworthy that phenolic compounds were detected in the ethyl acetate extract fraction. Furthermore, the primary phenolic compounds were also determined by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry. The possible fragmentation patterns have been proposed in positive and negative ion modes; the main fragment ions were observed from the loss of methyl, hydroxyl, or carboxyl groups. The compounds showed different fragmentation ions types in both positive and negative ionization modes and gave structural information on the main phenolic compounds in olive waste. The results of this study may be used to identify valuable active compounds and guide commercial applications of olive waste.     

Untersuchungen zur Synthese des Nodusmicin,I: Darstellung von (±)-(1R*,5R*,6R*,7S*8R*,9R*,10R*)-5-Acetyl-7,9-dibenzyloxy-10-hydroxy-8-methylbicyclo[4.4.0]decan-3-on

Summary Our first target on the way towards the synthesis of nodusmicin is the preparation of the title compound. Meso diol1 is partially etherified, then oxidized to the enone. The sterically compressed structure of this compound is the rationale of the highly stereoselective introduction of the substituents. (CH₃)₂CuLi introduces the methyl group and the enolate is captured as silylenol ether, which in turn is transformed to the -hydroxyketone by OsO₄. Reduction leads to the vicinaltrans diol. Protection of theexo-hydroxy group is followed by treatment with sodium in ethanol. Via intramolecular nucleophilic addition, substitution and dechlorination the tetracyclic diketal8 is formed. After exchange of the protective groups and partial hydrolysis of the ketals the tertiary alkohol is obtained with methyl Grignard reagent. Acidic fragmentation yields the desired title compound.

     

基于密度泛函理论的橘霉素衍生物质谱裂解行为研究

采用电喷雾离子阱质谱(ESI-IT-MSn),研究了橘霉素衍生物正离子模式下的裂解行为,并结合密度泛函理论(DFT)证明裂解途径的可靠性,为同类化合物的准确鉴定提供实验和理论基础。核磁共振仪对海莲内生真菌代谢产物分离得到的橘霉素衍生物结构进行确认,电喷雾离子阱质谱正离子模式扫描,测定化合物氢氘交换产物多级裂解质谱图,并结合键断裂能和Mulliken电荷分布,进一步验证裂解规律。实验结果表明,分子结构中-COOH和CH3COO-在一级裂解过程中易脱除CO2和COCH2,CID-MS2观测到丢失H2O/HDO、H2O和-CH3或CHCO/CDCO的碎片离子峰,且丰度依次降低,理论计算也证明,这些碎片离子的总能量依次增大,稳定性降低,键断裂能逐渐增大。该结果丰富了橘霉素衍生物的电喷雾质谱裂解规律,有助于橘霉素衍生物结构的准确鉴定,为该类化合物的检测和痕量分析提供了更多支持。     

Photoelectrochemical reduction of chlorinated nitrobenzenes: heavy atom versus radical ion lifetime effects

The photoelectrochemical behaviour of several chlorinated nitrobenzenes has been investigated using steady state channel flow cell methods. It has been shown that, in acetonitrile+0.1 M TBAHFP, 4-chloronitrobenzene (p-CNB), 2-chloronitrobenzene (o-CNB), 2,4-dichloronitrobenzene (2,4-DCNB), 2,6-dichloronitrobenzene (2,6-DCNB) and 1,3,5-trichloro-2-nitrobenzene (TCNB) can undergo reversible one-electron reductions to form radical anions that are stable on the timescale of at least tens of seconds under dark conditions. When the electrode surface is irradiated with light of intensity 2 mW cm⁻², the electrochemically formed radical anions can absorb light to form an excited state from which dechlorination is favoured. Reactivity orders of o-CNB>p-CNB>2,4-DCNB>2,6-DCNB>TCNB at 330 nm, and o-CNB>2,4-DCNB>2,6-DCNB>p-CNBTCNB at 470 nm have been determined. The relative order is rationalised in terms of radical anion lifetime effects and the role of heavy atom subsituents in reducing the excited state lifetime.     

Modelling the length distribution of etched tracks taking into account fragmentation due to partial annealing

Fission track length measurements on apatite minerals are of great interest in thermo-chronology studies. RBS analyses on Durango apatites irradiated by Krypton ions have previously shown the progressive fragmentation of tracks by annealing. This study made for different irradiation energies corresponding to those of uranium fission fragments has been completed by TEM and AFM on etched tracks. In all cases, segmentation figures have been observed, that clearly necessitates to introduce fragmentation of latent tracks to model the length distribution of uranium etched fission tracks. This presentation concerns the case of a homogeneous population of tracks with partial amorphization. The next step will consist in considering multiple sub-populations with different segmentation rates. This algorithm is a new aspect to be included in our model, which already takes into account diffusion and crystallography in the track etching process.     

5-乙氧羰基-4-取代-6-甲基-3,4-二氢嘧啶-2(1H)-酮的电子轰击飞行时间质谱表征

The electron ionization time-of-flight (TOF) mass spectra of a series of 5-ethoxycarbonyl-4-substituted-6-methyl-3,4-dihydropyrimidin-2(1H)-ones were studied to establish their fragmentation processes. Using the high resolution capabilities of the TOF instrument, exact masses for each fragment were determined. These data were used to infer molecular formulas and elemental compositions for all molecular ions and fragments through software interpretation and according to the established fragmentation rules the majority of ions were fully assigned. Two main fragmentation routes can be found in this work. First of them, for all the title compounds, includes the formation of three cations, by loss of R1 from the position 4, C2H4 (via a McLafferty rearrangement) from the ester group and H2O via a cyclic-six-membered transition state. The second route, for 4-aromatic compounds, consists of the formation of a cation by loss of EtCO2. Several additional fragmentations for individual compounds are proposed.     

Double hadron lepto-production in the current and target fragmentation regions

We study the inclusive production of two hadrons in deep inelastic processes, ?N→?h₁h₂X, with h₁ in the current fragmentation region (CFR) and h₂ in the target fragmentation region (TFR). Assuming a factorized scheme, the recently introduced polarized and transverse momentum dependent fracture functions couple to the transverse momentum dependent fragmentation functions. This allows the full exploration of the fracture functions for transversely polarized quarks. Some particular cases are considered.