bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of the DNA adducts induced by aristolochic acids in oligonucleotides by electrospray ionization tandem mass spectrometry
Authors: Chan Wan , Yue Hao , Wong Ricky N. S. , Cai Zongwei 
Published: November 2008

AbstractMetabolic activation of carcinogenic aristolochic acids (AA) produces reactive aristolactam‐nitrenium ion intermediates. Electrophilic attack of the aristolactam‐nitrenium ion via its C7 position to the exocyclic amino group in the purine bases leads to the formation of DNA adducts. DNA‐binding assays have demonstrated that carcinogens show site‐ and sequence‐specificity and the biological consequence is defined by the nature of binding as well as their position in the genome. In this study, electrospray ionization tandem mass spectrometry was applied for the identification and position mapping of DNA adducts in oligonucleotides (ODNs). The developed method was successfully applied for the analysis of unmodified and AA‐modified ODNs (5′‐TTTATT‐3′, 5′‐TTTGTT‐3′ and 5′‐TACATGTGT‐3′). The observation of the modified bases (modified adenine and guanine) together with the complementary product ions ([an‐B*n]−, w−) from the cleavage of the 3′ CO bond adjacent to the modified base in MS/MS analyses readily enabled the identification of the AA‐binding site in ODNs. Copyright © 2008 John Wiley & Sons, Ltd.
Using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry to rapidly screen for albuminuria
Authors: Shiea Jentaie , Cho Yi‐Tzu , Lin Yen‐Hsiu , Chang Chin‐Wen , Lo Li‐Hua , Lee Yi‐Chern , Ke Hung‐Lung , Wu Wen‐Jeng , Wu Deng‐Chyang 
Published: November 2008

AbstractMatrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) is used as an alternative method for the rapid diagnosis of albuminuria. This technique requires no further sample pretreatment than simply mixing the urine sample with a MALDI matrix and drying under ambient conditions. The resulting MALDI mass spectra reveal albumin ions having charges ranging from +1 to +5. The detection of albumin is possible using any of the three most common MALDI matrices – sinapinic acid (SA), 2,5‐dihydroxybenzoic acid (2,5‐DHB), or 4‐hydroxy‐α‐cyanocinnamic acid (α‐CHC). Using this analytical approach, the limit of detection for albumin in urine is 10−6 M, approximately 5 to 10 times lower than that detectable through conventional chemical testing. Copyright © 2008 John Wiley & Sons, Ltd.
Titanium dioxide anatase as matrix for matrix‐assisted laser desorption/ionization analysis of small molecules
Authors: Castro Ana L. , Madeira Paulo J. Amorim , Nunes Manuel R. , Costa Fernanda M. , Florêncio M. Helena 
Published: November 2008

AbstractThe use of inorganic species as assisting materials in matrix‐assisted laser desorption/ionization (MALDI) analysis is an alternative approach to avoid interfering matrix ions in the low‐mass region of the mass spectra. Reports of the application of inorganic species as matrices in MALDI analysis of small molecules are, however, scarce. Nevertheless, titanium dioxide (TiO2) powder has been reported to be a promising matrix medium. In this study we further explore the use of TiO2 as a matrix for the MALDI analysis of low molecular weight compounds. We present results showing that nanosized TiO2 anatase and TiO2 rutile perform better as MALDI matrices than a commercial TiO2 anatase/rutile mixture. Moreover, when using nanosized TiO2 anatase as a matrix, high‐quality mass spectra can be obtained with strong analyte signals and weak or non‐existing matrix interference ions. Furthermore, our results show that the phase type plays an important role in the application of TiO2 as a MALDI matrix. Copyright © 2008 John Wiley & Sons, Ltd.
On‐line coupling of liquid chromatography at critical conditions with electrospray ionization tandem mass spectrometry for the characterization of a nitroxide‐mediated poly(ethylene oxide)/polystyrene block copolymer
Authors: Girod Marion , Phan Trang N. T. , Charles Laurence 
Published: November 2008

AbstractCoupling of liquid chromatography at critical conditions (LCCC) with on‐line mass spectrometry (MS) detection was implemented via an electrospray ionization (ESI) interface, using a mobile phase containing the cationizing agent. Critical conditions established for poly(ethylene oxide) were used to characterize a poly(ethylene oxide)/polystyrene block copolymer (PEO‐b‐PS) in both MS and MS/MS modes. As co‐oligomer molecules were successfully separated according to the PS block size, structural information could be reached from simplified MS spectra. The microstructure of this copolymer, synthesized by nitroxide‐mediated polymerization, could further be unambiguously characterized in LCCC/ESI‐MS/MS experiments since the PS block size could be reached by both the co‐oligomer chromatographic behavior and its MS/MS pattern. Copyright © 2008 John Wiley & Sons, Ltd.
Precursor ion scan profiles of acylcarnitines by atmospheric pressure thermal desorption chemical ionization tandem mass spectrometry
Authors: Paglia Giuseppe , D'Apolito Oceania , Corso Gaetano 
Published: November 2008

AbstractThe fatty acyl esters of L‐carnitine (acylcarnitines) are useful biomarkers for the diagnosis of some inborn errors of metabolism analyzed by liquid chromatography/tandem mass spectrometry. In this study the acylcarnitines were analyzed by atmospheric pressure thermal desorption chemical ionization using a commercial tandem mass spectrometer (APTDCI‐MS/MS). The method is based on the precursor ion scan mode determination of underivatized acylcarnitines desorbed from samples by a hot desolvation gas flow and ionized by a corona pin discharge. During desorption/ionization step the temperature induces the degradation of acylcarnitines; nevertheless, the common fragment to all acylcarnitines [MH–59]+ is useful for analyzing their profile. APTDCI parameters, including angle of collection and incidence, gas flows and temperatures, were optimized for acylcarnitines. The experiments were performed drying 2 µL of an equimolar mixture of acylcarnitine standards on a glass slide. The specificity was evaluated by comparing product ion spectra and the precursor ion spectra of 85 m/z of acylcarnitines obtained by the APTDCI method and by electrospray ionization flow injection analysis (ESI‐FIA). The method was also employed to analyze acylcarnitines extracted from a pathological dried blood spot and a control. The method enables analysis of biological samples and recognition of some acylcarnitines that are diagnostic markers of inherited metabolic diseases. The intrinsic high‐throughput analysis of the ambient desorption ionization methods offers a new opportunity either for its potential application in clinical chemistry and for the expanded screening of some inborn errors of metabolism. Copyright © 2008 John Wiley & Sons, Ltd.
Application of gas chromatography/tandem quadrupole mass spectrometry to the multi‐residue analysis of pesticides in green leafy vegetables
Authors: Walorczyk Stanisław 
Published: November 2008

AbstractA new, sensitive and specific method has been developed for the simultaneous determination of 129 pesticides in lettuce and other green leafy vegetables. The samples were extracted with acetonitrile and co‐extractives such as fatty acids and pigments were removed using dispersive solid‐phase extraction (dispersive‐SPE) with primary secondary amine (PSA) and graphitized carbon black (GCB). All pesticides were analyzed in a single injection gas chromatography/tandem quadrupole mass spectrometry (GC/MS/MS) acquisition method. Two multiple reaction monitoring (MRM) transitions of precursor ions fragmenting into product ions were recorded for the targeted pesticides, thus fulfilling the EU identification points system criteria for the identification of contaminants (2002/657/EC). Calibration curves were determined using matrix‐matched standards, and exhibited excellent linearity at two orders of magnitude from 0.005 to 0.5 mg/kg for almost all the pesticides studied (R2 ≥ 0.99). The analytical performance was demonstrated by the analysis of lettuce samples spiked at five concentration levels ranging from 0.005 to 0.5 mg/kg for each pesticide. The recovery and repeatability results satisfied SANCO/2007/3131 criteria (i.e. average recoveries were in the range 70–120% with RSDs ≤20%) for 114 of the 129 pesticides at the 0.005 mg/kg spiking level, and for almost all pesticides at the higher spiking levels. The methodology was applied successfully to identify and quantify pesticide residues in leafy vegetable samples such as lettuce, cabbage and leek. Copyright © 2008 John Wiley & Sons, Ltd.
Silver complexation and tandem mass spectrometry for differentiation of triterpenoid saponins from the roots of Pulsatilla chinensis (Bunge) Regel
Authors: Cheng Lin , Zhang Min , Zhang Peng , Song Zhihang , Ma Zhongjun , Qu Haibin 
Published: November 2008

AbstractFor detection and differentiation of two types of triterpenoid saponins based on different aglycons of the lupane and oleanane skeleton from the roots of Pulsatilla chinensis (Bunge) Regel, the silver ion was introduced and electrospray ionization multi‐stage tandem mass spectrometry was applied to analyze eleven triterpenoid saponin silver complexes. The quasi‐molecular ion [M+Ag]+ was observed in the full‐scan MS spectra of all the silver complexes. The MS2 data of the [M+Ag]+ ion provided structural information on the sugar sequence of the oligosaccharide chains and the aglycon of the saponins. There are two patterns in the cleavage pathway of oleanane‐type saponins. One is elimination of the sugar chain and subsequent loss of the carboxylic group which is the same as the cleavage of lupine‐type saponins. The other is loss of the distinguishing ions at m/z 72 and 28 (C2H4) followed by loss of the carboxylic group. Diagnostic fragmentation pathways of the silver complexes of the saponins allow successful identification of the two types of saponins from the roots of Pulsatilla chinensis (Bunge) Regel. Copyright © 2008 John Wiley & Sons, Ltd.
Negative ion ‘chip‐based’ nanospray tandem mass spectrometry for the analysis of flavonoids in glandular trichomes of Lychnophora ericoides Mart. (Asteraceae)
Authors: Gobbo‐Neto Leonardo , Gates Paul J. , Lopes Norberto P. 
Published: November 2008

AbstractThis paper reports a method for the analysis of secondary metabolites stored in glandular trichomes, employing negative ion ‘chip‐based’ nanospray tandem mass spectrometry. The analyses of glandular trichomes from Lychnophora ericoides, a plant endemic to the Brazilian ‘cerrado’ and used in traditional medicine as an anti‐inflammatory and analgesic agent, led to the identification of five flavonoids (chrysin, pinocembrin, pinostrobin, pinobanksin and 3‐O‐acetylpinobanksin) by direct infusion of the extracts of glandular trichomes into the nanospray ionisation source. All the flavonoids have no oxidation at ring B, which resulted in a modification of the fragmentation pathways compared with that of the oxidised 3,4‐dihydroflavonoids already described in the literature. The absence of the anti‐inflammatory and antioxidant di‐C‐glucosylflavone vicenin‐2, or any other flavonoid glycosides, in the glandular trichomes was also demonstrated. The use of the ‘chip‐based’ nanospray QqTOF apparatus is a new fast and useful tool for the identification of secondary metabolites stored in the glandular trichomes, which can be useful for chemotaxonomic studies based on metabolites from glandular trichomes. Copyright © 2008 John Wiley & Sons, Ltd.
Characterization of metabolites of meisoindigo in male and female rat kidney microsomes by high‐performance liquid chromatography coupled with positive electrospray ionization tandem mass spectrometry
Authors: Huang Meng , Choo Lip‐Wee , Ho Paul C. 
Published: November 2008

AbstractMeisoindigo has been effectively applied for the treatment of chronic myelogenous leukemia (CML). Although the metabolic profile of meisoindigo has been studied in liver, information relevant to extrahepatic metabolism of meisoindigo is absent in kidney so far. In this study, the metabolism of meisoindigo in rat kidney microsomes was qualitatively and quantitatively investigated by liquid chromatography/tandem mass spectrometry (LC/MS/MS), in terms of metabolite identification, metabolic stability, metabolite formation and gender effect. The metabolic profiling was accomplished by integration of multiple reaction monitoring (MRM) with conventional full MS scan followed by MS/MS methodology. The majorin vitrometabolites of meisoindigo in rat kidney microsomes were identified as stereoselective 3,3′ double‐bond reduced meisoindigo, whereas the minor metabolites were regioselective phenyl monohydroxylmeisoindigo. An LC/MS/MS method for quantification of meisoindigo in rat kidney microsomes was also developed and validated. The calculatedin vitrohalf‐life (t1/2) values of meisoindigo in male and female rat kidney microsomes were 107.8 ± 17.0 min and 130.0 ± 12.9 min, respectively. There were no statistically significant differences between different genders in the metabolic stability profiles of meisoindigo. The reductive metabolite‐formation profiles of meisoindigo in male and female rat kidney microsomes were plotted semi‐quantitatively as well. The information regardingin vitrorenal metabolism of meisoindigo provided a better understanding of the role of the kidney in the disposition of meisoindigo. Copyright © 2008 John Wiley & Sons, Ltd.
A possible ethanol‐catalyzed rearrangement of vitamin K1 detected by gas chromatography/mass spectrometry
Authors: Osman Abdimajid , Hannestad Ulf 
Published: November 2008

AbstractWe studied vitamin K1(20), vitamin K1(25), and vitamin K1 epoxide in n‐hexane and ethanol solutions by gas chromatography/mass spectrometry (GC/MS) utilizing a DB‐5 MS fused‐silica capillary column. In ethanol solutions of K1, we observed an extra peak eluting from the GC column with somewhat longer retention time than K1(20). A similar peak following K1(25) was also found. These peaks were not found in n‐hexane solutions of K1. A close examination of the mass spectra of these peaks indicated that they were vitamin K1 variants containing a base peak at m/z 225 characteristic of the methylnaphthoquinone ring with a four‐carbon side chain. In addition, they contained the molecular ions of K1(20) and K1(25), respectively. We conclude that K1(20) and K1(25), but not K1 epoxide, might undergo rearrangements in ethanol involving an intramolecular proton transfer and a shift of the β,γ‐double bond on the phytyl side chain toward the ring. The conjugation of the phytyl double bond with the quinone ring is probably the driving force of the rearrangement. We emphasize, however, that our conclusion is based only on mass spectral analysis and would require further investigation by other spectroscopic methods. Copyright © 2008 John Wiley & Sons, Ltd.
Accelerator mass spectrometry of small biological samples
Authors: Salehpour Mehran , Forsgard Niklas , Possnert Göran 
Published: November 2008

AbstractAccelerator mass spectrometry (AMS) is an ultra‐sensitive technique for isotopic ratio measurements. In the biomedical field, AMS can be used to measure femtomolar concentrations of labeled drugs in body fluids, with direct applications in early drug development such as Microdosing. Likewise, the regenerative properties of cells which are of fundamental significance in stem‐cell research can be determined with an accuracy of a few years by AMS analysis of human DNA. However, AMS nominally requires about 1 mg of carbon per sample which is not always available when dealing with specific body substances such as localized, organ‐specific DNA samples. Consequently, it is of analytical interest to develop methods for the routine analysis of small samples in the range of a few tens of µg. We have used a 5 MV Pelletron tandem accelerator to study small biological samples using AMS. Different methods are presented and compared. A 12C‐carrier sample preparation method is described which is potentially more sensitive and less susceptible to contamination than the standard procedures. Copyright © 2008 John Wiley & Sons, Ltd.
Evaluation method for linking methamphetamine seizures using stable carbon and nitrogen isotopic compositions: a complementary study with impurity profiling
Authors: Iwata Yuko T. , Kuwayama Kenji , Tsujikawa Kenji , Miyaguchi Hajime , Kanamori Tatsuyuki , Inoue Hiroyuki 
Published: November 2008

AbstractDrug profiling, extraction of physical and/or chemical profiles from abused drug samples, is useful for inferring and characterizing links between samples originating from the same and different seizures, and supports drug crime investigations. We describe an evaluation method for linking methamphetamine (MA) seizures using stable carbon and nitrogen isotopic compositions concurrently with gas chromatographic impurity profiling, which is one of the major methods of drug profiling. Several sets of MA seized in Japan, whose investigative information indicated linkages, were analyzed. The impurity profile of each set of seizures was quite similar and hierarchical cluster analysis showed a sample classification that was relatively consistent with the investigative information. The stable carbon and nitrogen isotopic compositions of the MA seizures varied between −29.40 and −24.90 (δ13C) and −2.29 and 5.94 (δ15N), respectively. In the δ13C–δ15N graph, MA seizures were classified into seven groups, probably reflecting different origins. The size of the cluster in the isotopic‐composition graph was determined by pooled standard deviations (sp), the pooled estimates of measurement uncertainty. The sizes of the clusters were less than 6sp and the linkages between the MA seizures from the isotopic compositions were consistent with the impurity profiling and investigative information. The results showed that complementary use of stable‐isotopic compositions with impurity profiling provides useful information for evaluating the links between seizures. Copyright © 2008 John Wiley & Sons, Ltd.
Collisionally induced fragmentation of [M–H]− species of resveratrol and piceatannol investigated by deuterium labelling and accurate mass measurements
Authors: Stella Laura , De Rosso Mirko , Panighel Annarita , Vedova Antonio Dalla , Flamini Riccardo , Traldi Pietro 
Published: November 2008

AbstractResveratrol (3,5,4′‐trihydroxystilbene) and piceatannol (3,4,3′,5′‐tetrahydroxy‐trans‐stilbene) are phytoalexins present in red grapes and wines. In vitro studies have revealed that piceatannol blocks LMP2A, a viral protein‐tyrosine kinase implicated in leukemia, non‐Hodgkin's lymphoma and other diseases associated with the Epstein‐Barr virus, and has an antimelanoma effect on human melanoma cells. Resveratrol has several beneficial effects on human health, such as anticancer, cardioprotection, antioxidant, inhibition of platelet aggregation and anti‐inflammatory activity. In this investigation, the collisional behaviour of deprotonated resveratrol and piceatannol obtained under electrospray conditions is described. The mechanisms involved in the fragmentation pattern of [M–H]− species of the two compounds were investigated by performing MSn experiments, deuterium labelling and accurate mass measurements. Copyright © 2008 John Wiley & Sons, Ltd.
Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry monitoring of anthocyanins in extracts from Arabidopsis thaliana leaves
Authors: Marczak Łukasz , Kachlicki Piotr , Koźniewski Piotr , Skirycz Aleksandra , Krajewski Paweł , Stobiecki Maciej 
Published: November 2008

AbstractAnthocyanins are secondary plant metabolites ubiquitous in the plant kingdom. They have different biological activities, so monitoring their content in plant tissue or in feed/food derived from plants may be an important task in different projects from various fields of molecular biology and biotechnology. Profiling of secondary metabolites with high‐performance liquid chromatography/mass spectrometry (HPLC/MS) systems is time‐consuming, especially when many samples have to be checked within a defined time frame with a reasonable number of repetitions according to the metabolomic standards. Even application of the advanced ultra‐performance liquid chromatography (UPLC)/MS or equivalent systems would require a long time for analysis of numerous samples. We demonstrate the applicability of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) for the assessment of level (concentration) of anthocyanins in leaf tissues of four Arabidopsis thaliana ecotypes grown at normal (20°C/16°C day/night) and decreased (4°C) temperature. The quantitative results were obtained for anthocyanins with MALDI‐TOF MS using ferulic acid as a matrix. The amounts of anthocyanins in leaves of A. thaliana varied from 0.3–2.5 µg per gram of leaves for ecotypes Col‐0 and C24, respectively, and contents of these markedly increased in plants grown in the cold. The applied analytical method exhibited better repeatability of measurements than obtained with an HPLC/ion trap MS system. Copyright © 2008 John Wiley & Sons, Ltd.
A hypergraph regularity method for generalized Turán problems
Authors: Keevash Peter 
Published: November 2008

AbstractWe describe a method that we believe may be foundational for a comprehensive theory of generalized Turán problems. The cornerstone of our approach is a quasirandom counting lemma for quasirandom hypergraphs, which extends the standard counting lemma by not only counting copies of a particular configuration but also showing that these copies are evenly distributed. We demonstrate the power of the method by proving a conjecture of Mubayi on the codegree threshold of the Fano plane, that is, any 3‐graph onnvertices for which every pair of vertices is contained in more thann/2 edges must contain a Fano plane, fornsufficiently large. For projective planes over fields of odd sizeqwe show that the codegree threshold is betweenn/2 −q+ 1 andn/2, but forPG2(4) we find the somewhat surprising phenomenon that the threshold is less than (1/2 − ϵ)nfor some small ϵ > 0. We conclude by setting out a program for future developments of this method to tackle other problems. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009
Simultaneous Unsupervised Learning of Disparate Clusterings
Authors: Jain Prateek , Meka Raghu , Dhillon Inderjit S. 
Published: November 2008

AbstractMost clustering algorithms produce a single clustering for a given dataset even when the data can be clustered naturally in multiple ways. In this paper, we address the difficult problem of uncovering disparate clusterings from the data in atotally unsupervised manner. We propose two new approaches for this problem. In the first approach, we aim to find good clusterings of the data that are alsodecorrelatedwith one another. To this end, we give a new and tractable characterization of decorrelation between clusterings, and present an objective function to capture it. We provide an iterative “decorrelated”k‐means type algorithm to minimize this objective function. In the second approach, we model the data as a sum of mixtures and associate each mixture with a clustering. This approach leads us to the problem of learning a convolution of mixture distributions. Though the latter problem can be formulated as one of factorial learning8,13,16, the existing formulations and methods do not perform well on many real high‐dimensional datasets. We propose a new regularized factorial‐learning framework that is more suitable for capturing the notion of disparate clusterings in modern, high‐dimensional datasets. Furthermore, we provide kernelized version of both of our algorithms. The resulting algorithms do well in uncovering multiple clusterings, and are much improved over existing methods. We evaluate our methods on two real‐world datasets—a music dataset from the text‐mining domain, and a portrait dataset from the computer‐vision domain. Our methods achieve a substantially higher accuracy than existing factorial learning as well as traditional clustering algorithms. Copyright © 2008 Wiley Periodicals, Inc. Statistical Analysis and Data Mining 1: 000‐000, 2008