Distribution by Scientific Domains

Terms modified by MSn

  • msn data
  • msn experiment
  • msn spectrum

  • Selected Abstracts

    Characteristic fragmentation of bacteriohopanepolyols during atmospheric pressure chemical ionisation liquid chromatography/ion trap mass spectrometry

    Helen M. Talbot
    Bacteriohopanepolyols (BHPs) fragment via characteristic pathways during atmospheric pressure chemical ionisation liquid chromatography/ion trap mass spectrometry (APCI-LC/MSn). Comparison of the MS2 spectra of bacteriohopane-32,33,34,35-tetrol (BHT) and 2, -methylbacteriohopane-32,33,34,35-tetrol has confirmed the previously proposed ring-C cleavage occurring between C-9 and 11 and C-8 and 14. This fragmentation, diagnostic of all hopanoids, also occurs in BHPs containing an amino group (-NH2) at C-35 although the higher relative stability of the ion limits this fragmentation to a minor process after protonation of the basic nitrogen function. Studies of a number of cell cultures including a prochlorophyte (Prochlorothrix hollandica) and a cyanobacterium (Chlorogloeopsis LA) demonstrate the power of this technique to detect composite BHPs with a complex biological functionality at C-35. We also report the first observation of intact pentafunctionalised bacteriohopanepolyols using this method. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    Atmospheric pressure chemical ionisation reversed-phase liquid chromatography/ion trap mass spectrometry of intact bacteriohopanepolyols

    Helen M. Talbot
    Atmospheric pressure chemical ionisation liquid chromatography/multi-stage ion trap mass spectrometry (APCI-LC/MSn) has been applied to the study of intact bacteriohopanepolyols. Spectral characterisation of bacteriohopanepolyols of known structure present in bacterial extracts (Zymomonas mobilis and a fermenter containing methanotrophs including Methylococcus capsulatus) has revealed greater structural detail than previous liquid chromatography/mass spectrometry (LC/MS) methods and identified characteristic fragmentations indicative of numerous biohopanoid structures. Analysis of a Recent sedimentary extract from Lake Druzhby (Antarctica) has demonstrated the power of this technique to detect biohopanoids in complex samples including at least partial characterisation of previously unknown composite structures. Copyright © 2003 John Wiley & Sons, Ltd. [source]

    High-performance liquid chromatographic/tandem mass spectrometric identification of the phototransformation products of tebuconazole on titanium dioxide

    Paola Calza
    Abstract Tebuconazole is a widely used fungicide. The formation of by-products on irradiated titanium dioxide as a photocatalyst was evaluated. Several species derived from tebuconazole degradation were identified and characterized by HPLC/MSn. A pattern of reactions accounting for the observed intermediates is proposed. Different parallel pathways are operating (and through these pathways the transformation of the molecule proceeds), leading to a wide range of intermediate compounds. All these molecules are more hydrophylic than tebuconazole. The main steps involved are (1) the hydroxylation of the molecule with the formation of three species having [M + H]+ 324; the hydroxylation occurs on the C-1 carbon and on the aromatic ring in the two ortho -positions; (2) the cleavage of a C,C bond with the release of the tert -butyl moiety and the formation of a species having m/z 250; analogously to step 1, also on this species a further hydroxylation reaction occurs; (3) through the loss of the triazole moiety with the formation of a structure with m/z 257. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Metabolism of a sulfur-containing heteroarotionoid antitumor agent, SHetA2, using liquid chromatography/tandem mass spectrometry

    Zhongfa Liu
    SHetA2 {[(4-nitrophenyl)amino][2,2,4,4-tetramethylthiochroman-6-yl)amino]methanethione], NSC 726189}, a sulfur-containing heteroarotinoid, selectively inhibits cancer cell growth and induces apoptosis without activation of nuclear retinoic acid receptors (RARs). The objective of this study was to investigate its in vitro metabolism in rat and human liver microsomes and in vivo metabolism in the mouse and rat using liquid chromatography-ultraviolet/multi-stage mass spectrometry (LC-UV/MSn) on an ion-trap mass spectrometer coupled with a photo-diode array (PDA) detector. In vitro, in the absence of glutathione (GSH), oxidation of the four aliphatic methyl groups of SHetA2 yielded one mono-, two di-, and one tri-hydroxylated SHetA2 metabolites, which were identified based on their UV and multi-stage mass spectra. In the presence of GSH, in addition to these primary oxidative metabolites, four GSH adducts of SHetA2 and a novel rare form thioether GSH adduct was detected and characterized. In vivo, the monohydroxylated SHetA2 metabolites were also detected in mouse and rat plasma and two GSH adducts were detected in rat liver following intravenous (i.v.) bolus administration of SHetA2 at 40,mg/kg. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Hierarchical scheme for liquid chromatography/multi-stage spectrometric identification of 3,4,5-triacyl chlorogenic acids in green Robusta coffee beans

    Rakesh Jaiswal
    Liquid chromatography/multi-stage spectrometry (LC/MSn) (n,=,2,4) has been used to detect and characterize in green Robusta coffee beans eight quantitatively minor triacyl chlorogenic acids with seven of them not previously reported in nature. These comprise 3,4,5-tricaffeoylquinic acid (Mr 678); 3,5-dicaffeoyl-4-feruloylquinic acid, 3-feruloyl-4,5-dicaffeoylquinic acid and 3,4-dicaffeoyl-5-feruloylquinic acid (Mr 692); 3-caffeoyl-4,5-diferuloylquinic acid and 3,4-diferuloyl-5 - caffeoylquinic acid (Mr 706); and 3,4-dicaffeoyl-5-sinapoylquinic acid and 3-sinapoyl-4,5-dicaffeoylquinic acid (Mr 722). Structures have been assigned on the basis of LC/MSn patterns of fragmentation. A new hierarchical key for the identification of triacyl quinic acids is presented, based on previously established rules of fragmentation. Fifty-two chlorogenic acids have now been characterized in green Robusta coffee beans. In this study five samples of green Robusta coffee beans and fifteen samples of Arabica coffee beans were analyzed with triacyl chlorogenic acids only found in Robusta coffee bean extracts. These triacyl chlorogenic acids could be considered as useful phytochemical markers for the identification of Robusta coffee beans. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Metabolite identification of a new antitumor agent icotinib in rats using liquid chromatography/tandem mass spectrometry

    Zhongmin Guan
    Icotinib, 4-[(3-ethynylphenyl)amino]-6,7-benzo-12-crown-4-quinazoline, is a new antitumor agent. The metabolic pathway of icotinib in rats was studied using liquid chromatography/tandem mass spectrometry (LC/MSn) analysis. Full scan and selected ion monitoring modes were used to profile the possible metabolites of icotinib in rat urine, feces and bile samples. Four phase I metabolites (M1,M4) and two phase II metabolites (M5, M6) were detected and characterized. Multiple-stage mass spectrometry and nuclear magnetic resonance (NMR) spectrometry were employed to elucidate structures of metabolites. Icotinib was metabolized to open the crown ether ring to form the main phase I metabolites. During metabolism, a reactive metabolite was formed. Using semicarbazide as a trapping agent, an intermediate arising from opening of the crown ether ring was detected as an aldehyde product by LC/MS/MS. These data indicated that ring opening of the crown ether was triggered by hydroxylation at the 8,-position of the ring to form a hemiacetal intermediate, which was further oxidized or reduced. Finally, the metabolic pathway of icotinib in rats was proposed. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Characterization of covalent addition products of chlorogenic acid quinone with amino acid derivatives in model systems and apple juice by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry

    Susanne Schilling
    High-performance liquid chromatography (HPLC) coupled to electrospray ionization tandem mass spectrometry (ESI-MSn) was used to study the covalent interactions between chlorogenic acid (CQA) quinone and two amino acid derivatives, tert -butyloxycarbonyl-L-lysine and N -acetyl-L-cysteine. In a model system at pH 7.0, the formation of covalent addition products was demonstrated for both derivatives. The addition product of CQA dimer and tert -butyloxycarbonyl-L-lysine was characterized by LC/MSn as a benzacridine structure. For N -acetyl-L-cysteine, mono- and diaddition products at the thiol group with CQA quinone were found. In apple juice at pH 3.6, covalent interactions of CQA quinone were observed only with N -acetyl-L-cysteine. Taking together these results and those reported by other groups it can be concluded that covalent interactions of amino side chains with phenolic compounds could contribute to the reduction of the allergenic potential of certain food proteins. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Identification of 1-hydroxypyrene glucuronide in tissue of marine polychaete Nereis diversicolor by liquid chromatography/ion trap multiple mass spectrometry

    Anders M. B. Giessing
    1-Hydroxypyrene glucuronide is identified as the single major aqueous metabolite of the tetracyclic aromatic hydrocarbon pyrene, in tissue from a deposit-feeding marine polychaete, Nereis diversicolor. Identification was performed using an ion trap mass spectrometer fitted with an atmospheric pressure chemical ionization (APCI) probe and connected to a high-performance liquid chromatography/diode array detector (HPLC/DAD) system. Besides 1-hydroxypyrene, the 339-nm UV trace of tissue samples from pyrene-exposed worms showed only one dominant peak that could be related to pyrene metabolism. Negative APCI-MS of this supposed 1- hydroxypyrene conjugate gave a characteristic signal at m/z 429 corresponding to the molecular ion of 1-hydroxypyrene glucuronide plus eluent adducts ([M,,,H,+,2H2O],). Fragmentation pathways were studied by isolating the abundant ion at m/z 429 in the ion trap and performing multiple mass spectrometric experiments (MSn). The fragmentations observed were consistent with the proposed identification. Two low intensity LC peaks that could be related to pyrene metabolism by their DAD absorption spectra were also present in the 339-nm UV chromatogram of tissue samples. However, these peaks could not be identified by their mass spectra in negative ion mode due to ion suppression by very abundant co-eluting impurities. The present method shows that LC/MSn is a fast and useful analytical tool for identification of aqueous polycyclic aromatic hydrocarbon biotransformation products in samples from relatively small marine invertebrates with limited sample preparation. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Collision-induced dissociation of glycero phospholipids using electrospray ion-trap mass spectrometry

    Åsmund Larsen
    Characterisation of phospholipids was achieved using collision-induced dissociation (CID) with an ion-trap mass spectrometer. The product ions were compared with those obtained with a triple quadrupole mass spectrometer. In the negative ion mode the product ions were mainly sn -1 and sn -2 lyso-phospholipids with neutral loss of ketene in combination with neutral loss of the polar head group. Less abundant product ions were sn -1 and sn -2 carboxylate anions. CID using a triple quadrupole mass spectrometer, however, gave primarily the sn -1 and sn -2 carboxylate anions together with lyso-phosphatidic acid with neutral loss of water. For the ion trap a charge-remote-type mechanism is proposed for formation of the lyso-phospholipid product ions by loss of ,-hydrogen on the fatty acid moiety, electron rearrangement and neutral loss of ketene. A second mechanism involves nucleophilic attack of the phosphate oxygen on the sn -1 and sn -2 glycerol backbone to form carboxylate anions with neutral loss of cyclo lyso-phospholipids. CID (MS3 and MS4) of the lyso-phospholipids using the ion-trap gave the same carboxylate anions as those obtained with a triple quadrupole instrument where multiple collisions in the collision cell are expected to occur. The data demonstrate that phospholipid species determination can be performed by using LC/MSn with an ion-trap mass spectrometer with detection of the lyso-phospholipid anions. The ion-trap showed no loss in sensitivity in full scan MSn compared to multiple reaction monitoring data acquisition. In combination with on-line liquid chromatography this feature makes the ion-trap useful in the scanning modes for rapid screening of low concentrations of phospholipid species in biological samples as recently described (Uran S, Larsen,Å, Jacobsen PB, Skotland T. J. Chromatogr. B 2001; 758: 265). Copyright © 2001 John Wiley & Sons, Ltd. [source]

    PRECLINICAL STUDY: FULL ARTICLE: Altered architecture and functional consequences of the mesolimbic dopamine system in cannabis dependence

    ADDICTION BIOLOGY, Issue 3 2010
    Saturnino Spiga
    ABSTRACT Cannabinoid withdrawal produces a hypofunction of mesencephalic dopamine neurons that impinge upon medium spiny neurons (MSN) of the forebrain. After chronic treatment with two structurally different cannabinoid agonists, ,9 -tetrahydrocannabinol and CP55 940 (CP) rats were withdrawn spontaneously and pharmacologically with the CB1 antagonist SR141716A (SR). In these two conditions, evaluation of tyrosine hydroxylase (TH)-positive neurons revealed significant morphometrical reductions in the ventrotegmental area but not substantia nigra pars compacta of withdrawn rats. Similarly, confocal analysis of Golgi,Cox-stained sections of the nucleus accumbens revealed a decrease in the shell, but not the core, of the spines' density of withdrawn rats. Administration of the CB1 antagonist SR to control rats, provoked structural abnormalities reminiscent of those observed in withdrawal conditions and support the regulatory role of cannabinoids in neurogenesis, axonal growth and synaptogenesis by acting as eu-proliferative signals through the CB1 receptors. Further, these measures were incorporated into a realistic computational model that predicts a strong reduction in the excitability of morphologically altered MSN, yielding a significant reduction in action potential output. These pieces of evidence support the tenet that withdrawal from addictive compounds alters functioning of the mesolimbic system and provide direct morphological evidence for functional abnormalities associated with cannabinoid dependence at the level of dopaminergic neurons and their postsynaptic counterpart and are coherent with recent hypothesis underscoring a hypodopaminergic state as a distinctive feature of the ,addicted brain'. [source]

    Non-muscle myosin heavy chain (MYH9): A new partner fused to ALK in anaplastic large cell lymphoma

    Laurence Lamant
    In anaplastic large cell lymphoma, the ALK gene at 2p23 is known to be fused to NPM, TPM3, TPM4, TFG, ATIC, CLTC, MSN, and ALO17. All of these translocations result in the expression of chimeric ALK transcripts that are translated into fusion proteins with tyrosine kinase activity and oncogenic properties. We report a case showing a restricted cytoplasmic staining pattern of ALK and a novel chromosomal abnormality, t(2;22)(p23;q11.2), demonstrated by fluorescence in situ hybridization analysis. The result of 5, RACE analysis showed that the ALK gene was fused in-frame to a portion of the non-muscle myosin heavy chain gene, MYH9. Nucleotide sequence of the MYH9-ALK chimeric cDNA revealed that the ALK breakpoint was different from all those previously reported. It is localized in the same exonic sequence as MSN-ALK, but 6 bp downstream, resulting in an in-frame fusion of the two partner proteins. In contrast to the previously reported ALK fusion proteins, MYH9-ALK may lack a functional oligomerization domain. However, biochemical analysis showed that the new fusion protein is tyrosine phosphorylated in vivo but seems to lack tyrosine kinase activity in vitro. If further investigations confirm this latter result, the in vivo tyrosine phosphorylation of MYH9-ALK protein could involve mechanisms different from those described in the other ALK hybrid proteins. © 2003 Wiley-Liss, Inc. [source]

    Near-Infrared Mesoporous Silica Nanoparticles for Optical Imaging: Characterization and In Vivo Biodistribution

    Chia-Hung Lee
    Abstract The characterization of near-infrared (NIR) mesoporous silica nanoparticles (MSN) suitable for in vivo optical imaging with high efficiency is presented. Trimethylammonium groups modified MSN (MSN-TA) with the average size of 50,100,nm was synthesized with incorporation of the TA groups into the framework of MSN. It was further adsorbed with indocyanine green (ICG) by electrostatic attraction to render MSN-TA-ICG as an efficient NIR contrast agent for in vivo optical imaging. The studies in stability of MSN-TA-ICG against pH indicated the bonding is stable over the range from acidic to physiological pH. The in vivo biodistribution of MSN-TA-ICG in anesthetized rat demonstrated a rather strong and stable fluorescence of MSN-TA-ICG that prominent in the organ of liver. Transmission electron microscopy (TEM) imaging and elemental analysis of silicon further manifested the physical and quantitative residences of MSN-TA-ICG in major organs. This is the first report of MSN functionalized with NIR-ICG capable of optical imaging in vivo. [source]

    Ineffective Peripheral Tissue Perfusion: Clinical Validation in Patients With Hypertensive Cardiomiopathy

    Rita de Cassia Gengo de Silva MS
    PURPOSE.,To validate defining characteristics of ineffective peripheral tissue perfusion using vasomotor function assessment. METHODS.,Twenty-four patients with hypertensive cardiomiopathy were evaluated for 18 defining characteristics of ineffective peripheral tissue perfusion and underwent vasomotor function assessment with induction of reactive hyperemia, intra-arterial infusion of acetylcholine, and pulse wave velocity measurement. The Student's t test and Kruskall,Wallis test were used to assess the significance of relationships between defining characteristics and vasomotor function data. FINDINGS.,Diminished lower extremity pulses were associated with diminished forearm blood flow during acetylcholine infusion; left ventricular overload, intermittent claudication, and diminished skin moisture were associated with elevated pulse wave velocity values. CONCLUSION.,The defining characteristics of ineffective peripheral tissue perfusion were highly associated with vasomotor function data as "gold standards" for that diagnosis. PRACTICE IMPLICATIONS.,Nurses should be able to accurately assess diminished lower extremity pulses, intermittent claudication, and diminished skin moisture as relevant characteristics of ineffective peripheral tissue perfusion in patients with hypertensive cardiomiopathy. Irrigation Tissulaire Périphérique Inefficace: Validation Clinique Chez les Patients Atteints de Cardiomyopathie Hypertensive BUT.,Valider les caractéristiques de Irrigation tissulaire périphérique inefficace en utilisant l'évaluation de la fonction vasomotrice. MÉTHODES.,Vingt-quatre patients souffrant de cardiomyopathie hypertensive furent évalués au regard des 18 caractéristiques du diagnostic Irrigation vasculaire périphérique inefficace et de la fonction vasomotrice par induction d'une hyperémie réactionnelle, la perfusion intra-artérielle d'acétylcholine, et la mesure de la vélocité de l'onde du pouls. Les tests "Student t et Kruskall,Wallis" furent utilisés pour déterminer l'importance des liens entre les caractéristiques et les valeurs de la fonction vasomotrice. RÉSULTATS.,La diminution des pulsations périphériques des membres inférieurs fut associée à une diminution du flot sanguin pendant la perfusion d'acétylcholine; une surcharge ventriculaire gauche, de la claudication intermittente et une diminution de l'hydratation de la peau furent associées à des valeurs élevées de la vélocité de l'onde du pouls. CONCLUSION.,,Les caractéristiques de Irrigation tissulaire périphérique inefficace qui furent associées de manière significative à la fonction vasomotrice peuvent être considérées comme les "étalons or" de ce diagnostic. IMPLICATIONS POUR LA PRATIQUE.,Les infirmières devraient être capables d'évaluer correctement la diminution des pouls périphériques, la claudication intermittente, et la diminution de l'hydratation de la peau, car ce sont des caractéristiques pertinentes de l'irrigation tissulaire périphérique inefficace chez les patients atteints de cardiomyopathie hypertensive. Translation by Cécile Boisvert, MSN, RN Perfusão Tissular Periférica Ineficaz: Validação Clínica em Pacientes com Miocardiopatia Hipertensiva PROPÓSITO.,Validar as caraterísticas definidoras do diagnóstico de perfusão tissular periférica ineficaz usando a avaliação da função vasomotora. MÉTODO.,Vinte e quatro pacientes com miocardiopatia hipertensiva foram avaliados segundo 18 características definidoras de perfusão tissular periférica ineficaz e submetidos a avaliação da função vasomotora por indução de hiperemia reativa, infusão intra-arterial de acetilcolina e por mensuração da velocidade da onda de pulso. Testes T de Student e de Kruskall,Wallis foram aplicados para avaliar a significância das relações entre as características definidoras e os dados da função vasomotora. RESULTADOS.,Diminuição de pulso nas extremidades inferiores foi associada com o menor fluxo de sangue no antebraço durante a infusão de acetilcolina; sobrecarga ventricular esquerda, claudicação intermitente e diminuição da hidratação da pele foram associados com valores elevados de velocidade de onda de pulso. CONCLUSÃO.,Quatro características definidoras de perfusão tissular periférica ineficaz foram altamente associadas com função vasomotora alterada como "padrão ouro" para este diagnóstico. IMPLICAÇÕES PARA A PRÁTICA.,As enfermeiras devem ser capazes de avaliar com precisão a diminuição dos pulsos das extremidades inferiores, claudicação intermitente e diminuição na hidratação da pele como características definidoras relevantes da perfusão tissular periférica ineficaz em pacientes com miocardiopatia hipertensiva. Translation by Alba Leite de Barros, PhD, RN Perfusión Tisular Periférica Inefectiva: Validación Clínica en Pacientes que Presentan Miocardiopatía Hipertensiva PROPÓSITO.,Validar las características definitorias del diagnóstico Perfusión tisular periférica inefectiva utilizando una valoración de la función vasomotora. METODOLOGÍA.,Veinticuatro pacientes diagnosticados de Miocardiopatía Hipertensiva fueron evaluados con respecto a las 18 características definitorias del diagnóstico Perfusión tisular periférica inefectiva y sometidos a una valoración de la función vasomotora con inducción de Hiperemia reactiva, infusión intra-arterial de acetilcolina, y medida de la velocidad de la onda del pulso. Se utilizaron los análisis estadísticos de t-Student y Kruskall,Wallis para valorar el significado de las relaciones entre las características definitorias y los datos obtenidos de la valoración de la función vasomotora. HALLAZGOS.,Durante la infusión de acetilcolina se detectó disminución de los pulsos en la extremidad inferior relacionado con la disminución del volumen de sangre en el antebrazo; la sobrecarga ventricular izquierda, claudicación intermitente y disminución de la hidratación de la piel fueron asociadas con la elevación de los valores de la velocidad de la onda del pulso. CONCLUSIÓN.,Las características definitorias del diagnóstico Perfusión tisular periférica inefectiva estaban fuertemente asociadas a los datos procedentes de la valoración de la función vasomotora identificándose como "estándares fundamentales" para este diagnóstico. IMPLICACIONES PARA LA PRÁCTICA.,Las enfermeras deberían ser capaces de valorar cuidadosamente la presencia de pulsos disminuidos en las extremidades inferiores, y la disminución de la hidratación de la piel ya que son características relevantes del diagnóstico Perfusión tisular periférica inefectiva en pacientes que presentan Miocardiopatía Hipertensiva. Translation by Adolf Guirao, RN [source]

    Comparison of Nursing Interventions Performed by Medical-Surgical Nurses in Korea and the United States

    Eunjoo Lee PhD
    PURPOSE.,To compare the Nursing Interventions Classification (NIC) interventions used in two countries, Korea and the United States. METHODS.,Data were collected from 167 nurses working in eight hospitals in Korea and analyzed with descriptive statistics. FINDINGS.,Korean nurses selected 202 interventions, nine of which were used by more than 50% of nurses surveyed. In comparison, the Academy of Medical-Surgical Nurses (AMSN) in the United States identified 68 interventions as core interventions. Among the top ranked 68 interventions selected by Korean nurses, 29 (43%) matched those selected by U.S. nurses. CONCLUSION.,The nursing interventions selected by Korean nurses were more heavily focused on the physiologic domain than those selected by the U.S. nurses. PRACTICE IMPLICATIONS.,The identified intervention lists can be used to develop nursing information systems, staff education, competency evaluation, referral networks, certification and licensing exams, and educational curricula for nursing students. Comparaison des interventions réalisées par les infirmières de Médecine-Chirurgie en Corée et aux Etats-Unis BUTS.,Comparer les interventions (tirées de la Classification des Interventions) utilisées dans deux pays: La Corée et les Etats-Unis. MÉTHODES.,Les données furent collectées auprès de 167 infirmières travaillant dans huit hôpitaux Coréens et furent analysées à l'aide de statistiques descriptives. RÉSULTATS.,Les infirmières Coréennes ont choisi 202 interventions, neuf d'entre elles furent utilisées par plus de 50% des infirmières incluses dans l'étude. En comparaison, l'Académie des Infirmières en Médecine-Chirurgie (E.U.) ont identifié 68 interventions clés. Parmi les 68 premières interventions choisies par les infirmières Coréennes, 29 (43%) correspondent à celles qui ont été choisies par les infirmières Américaines. CONCLUSION.,Les interventions de soins choisies par les infirmières Coréennes furent plus fortement centrées sur les domaines physiologiques que celles choisies par leurs collègues Américaines. IMPLICATIONS POUR LA PRATIQUE.,Les listes d'interventions identifées peuvent être utilisées pour développer des systèmes d'information, la formation du personnel, l'évaluation de la compétence, les réseaux de soin, les examens de certification et les programmes de formation des étudiantes infirmières. Translation by Cécile Boisvert, MSN, RN Comparação das Intervenções Realizadas por Enfermeiras Médico-Cirúrgicas na Coréia e nos Estados Unidos OBJETIVO.,Comparar as intervenções contidas na classificação de intervenções de Enfermagem (NIC) usadas nos dois paises, Coréia e Estados Unidos. MÉTODOS.,Os dados foram coletados com 167 enfermeiras que trabalhavam em oito hospitais na Coréia e analisadas com estaticista descritiva. RESULTADOS.,As enfermeiras coreanas selecionaram 202 intervenções, nas quais foram usadas por mais de 50% das enfermeiras entrevistadas. Em comparação, a Academia de enfermeiras médico-cirúrgicas (AMSN) nos Estados Unidos identificaram 68 intervenções como principais. Dentre as 68 intervenções como principais. Dentre as 68 intervenções mais importantes selecionadas pelas enfermeiras coreanas, 29 (43%) coincidiram com aquelas selecionadas pelas enfermeiras americanas. CONCLUSÃO.,As intervenções selecionadas pelas enfermeiras coreanas foram mais fortemente focadas no domínio fisiológico do que aquelas selecionadas pelas enfermeiras americanas. IMPLICAÇÕES PARA A PRÁTICA.,As listas das intervenções identificadas pode ser usada para o desenvolvimento de sistemas de informação de enfermagem, educação-permanente da equipe, avaliação da competência, rede de referências, exames de certificação e licença e currículo educacional para estudantes de enfermagem. Translation by Alba Leite de Barros, PhD, RN Estudio Comparativo de las Intervenciones Enfermeras Realizadas por Enfermeras Especialistas Médico-Quirúrgicas en Korea y Estados Unidos (EUA) PROPÓSITO.,Realizar un estudio comparativo entre las intervenciones enfermeras de la taxonomía NIC (Clasificación de las Intervenciones Enfermeras) utilizadas en dos países, Korea y EUA. METODOLOGÍA.,Los datos fueron recogidos entre 167 enfermeras que trabajaban en ocho hospitales de Korea y fueron analizadas utilizando medidas estadísticas descriptivas. HALLAZGOS.,Las enfermeras koreanas seleccionaron 202 intervenciones, nueve de las cuales fueron utilizadas por más del 50% de las enfermeras estudiadas. A diferencia, la Academia de Enfermeras especialistas Médico-quirúrgicas (AMSN) de los EUA, había identificado 68 intervenciones enfermeras. Entre las 68 intervenciones seleccionadas más frecuentemente por las enfermeras koreanas, 29 (43%) coincidían con las seleccionadas por las enfermeras americanas. CONCLUSIÓN.,Las intervenciones seleccionadas por las enfermeras koreanas estaban más centradas en el dominio fisiológico que las seleccionadas por las enfermeras americanas. IMPLICACIONES PARA LA PRÁCTICA.,La lista de intervenciones identificadas puede ser utilizada para desarrollar sistemas de información enfermeros, programas de formación, evaluación de la competencia, redes de enfermeras de referencia, exámenes de certificación y obtención de licencias, y currícula de formación para los estudiantes de enfermería. Translation by Adolf Guirao, RN [source]

    ,On MSN with buff boys': Self- and other-identity claims in the context of small stories1

    Alexandra Georgakopoulou
    This is a study of self- and other-identity claims such as ascriptions, assessments and categorizations in the classroom interactional data of female adolescent students of a London comprehensive school. The study follows an identities-in-interaction approach and attends to the occurrence of identity claims in stories of recent mediated interactions (e.g. on MSN, by text) between tellers and male suitors, which I collectively call small stories. In a narrative-interactional analysis of such claims in two small stories, I postulate a distinction between taleworld and telling identity claims that allows me to show how the sequential context of the claims has implications for their interactional uptake. I specifically focus on the relational organization of the identity claims in contrastive pairs of positive and negative attributes and on their contribution to the stories' tellership rights and tellability. My main aim is to show how identity claims can be intimately linked with and discursively invoke solidified roles (cf. known, habitual) that hold above and beyond the local context. I argue that the three interactional features of iterativity, narrativity and stylization hold the key to uncovering the links between identity claims with solidified roles. [source]

    A morphometric approach to the geographic variation of the terrestrial isopod species Armadillo tuberculatus (Isopoda: Oniscidea)

    M. Kamilari
    Abstract The terrestrial isopod species Armadillo tuberculatus Vogl, 1876 (Crustacea, Isopoda, Oniscidea) is a widely polymorphic species distributed in the south-central Aegean region (Greece) with a different morph on each island. Variation consists in coloration, size of cuticular tubercules, shape of telson and the shape of the male first pleopod exopodite (secondary sexual character of taxonomic importance). We studied the allometric growth of a cuticular tubercule in 17 populations (for both male and female individuals) and the shape variation of the first male pleopod exopodite in 10 populations using Elliptic Fourier Analysis, in order to test for patterns of intraspecific variation and possible relationships between morphs. In addition, Thin Plate Spline analysis was used for the calculation of the minimum bending energy between different exopodite shapes, which was then used for estimating the minimum spanning network (MSN) connecting them. The different allometric growth rates of the tubercule among island groups were significantly related to island latitude and climatic factors. On the other hand, the clustering of islands and the MSN based on male exopodite shape differences were not related to the palaeogeography of the Aegean region or to the present geographic distances of islands. These results are interpreted as evidence for non-adaptive radiation of the morphs. Resumen El isópodo terrestre Armadillo tuberculatus Vogl, 1876 (Crustacea, Isopoda, Oniscidea) es una especie extensamente polimórfica distribuida por la región sur-central del piélago Egéo (Grecia), con una forma distinta en cada isla. Se trata de variaciones en la coloración, el tamaño de los tubérculos cuticulares y en la forma del primer exopodio masculino del pleopodo (carácter sexual secundario de importancia taxonómica). Estudiamos el crecimiento alométrico del tubérculo cuticular en 17 poblaciones (en individuos de ambos sexos) y la variación de la forma del primer exopodio masculino del pleopodo en 10 poblaciones según el análisis de Fourier elíptico (Elliptic Fourier Analysis) para detectar patrones de variación intraespecifica y relaciones posibles entre las formas de la especie. Además, el análisis Thin Plate Spline fue utilizado para el cálculo de la Energía de Flexión Mínima (Minimum Bending Energy) entre diversas formas del exopodio, que entonces fue utilizada para estimar la Mínima Red de Distancias (Minimum Spanning Network, MSN) que las conectaba. Detectamos una correlación significativa entre las diversas tasas de crecimiento alométrico del tubérculo entre los grupos de islas y la latitud de la isla. Por otro lado, la agrupación de las islas y la MSN, basada en las diferencias de la forma del exopodio, no fueron relacionados con la paleogeografía de la región del piélago Egéo ni con las actuales distancias geográficas de las islas. Estos resultados se interpretan como evidencia para la radiación non-adaptativa de las diversas formas de la especie. [source]

    Evidence of cell-nonautonomous changes in dendrite and dendritic spine morphology in the met-signaling,deficient mouse forebrain

    Matthew C. Judson
    Abstract Human genetic findings and murine neuroanatomical expression mapping have intersected to implicate Met receptor tyrosine kinase signaling in the development of forebrain circuits controlling social and emotional behaviors that are atypical in autism-spectrum disorders (ASD). To clarify roles for Met signaling during forebrain circuit development in vivo, we generated mutant mice (Emx1Cre/Metfx/fx) with an Emx1-Cre-driven deletion of signaling-competent Met in dorsal pallially derived forebrain neurons. Morphometric analyses of Lucifer yellow-injected pyramidal neurons in postnatal day 40 anterior cingulate cortex (ACC) revealed no statistically significant changes in total dendritic length but a selective reduction in apical arbor length distal to the soma in Emx1Cre/Metfx/fx neurons relative to wild type, consistent with a decrease in the total tissue volume sampled by individual arbors in the cortex. The effects on dendritic structure appear to be circuit-selective, insofar as basal arbor length was increased in Emx1Cre/Metfx/fx layer 2/3 neurons. Spine number was not altered on the Emx1Cre/Metfx/fx pyramidal cell populations studied, but spine head volume was significantly increased (,20%). Cell-nonautonomous, circuit-level influences of Met signaling on dendritic development were confirmed by studies of medium spiny neurons (MSN), which do not express Met but receive Met-expressing corticostriatal afferents during development. Emx1Cre/Metfx/fx MSN exhibited robust increases in total arbor length (,20%). As in the neocortex, average spine head volume was also increased (,12%). These data demonstrate that a developmental loss of presynaptic Met receptor signaling can affect postsynaptic morphogenesis and suggest a mechanism whereby attenuated Met signaling could disrupt both local and long-range connectivity within circuits relevant to ASD. J. Comp. Neurol. 518:4463,4478, 2010. © 2010 Wiley-Liss, Inc. [source]

    Temporal aggregation of Markov-switching financial return models

    Wai-Sum Chan
    Abstract In this paper we investigate the effects of temporal aggregation of a class of Markov-switching models known as Markov-switching normal (MSN) models. The growing popularity of the MSN processes in modelling financial returns can be attributed to their inherited flexibility characteristics, allowing for heteroscedasticity, asymmetry and excess kurtosis. The distributions of the process described by the basic MSN model and the model of the corresponding temporal aggregate data are derived. They belong to a general class of mixture normal distributions. The limiting behaviour of the aggregated MSN model, as the order of aggregation tends to infinity, is studied. We provide explicit formulae for the volatility, autocovariance, skewness and kurtosis of the aggregated processes. An application of measuring solvency risk with MSN models for horizons larger than 1 year and up to 10 years from the baseline U.S. S&P 500 stock market total return time series spanning about 50 years is given. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    In vitro Studies of Functionalized Mesoporous Silica Nanoparticles for Photodynamic Therapy

    ADVANCED MATERIALS, Issue 2 2009
    Hsiung-Lin Tu
    A versatile platform for photodynamic therapy (PDT), mesoporous silica nanoparticles functionalized with protoporphyrin IX (PpIX-MSNs), has been developed. In vitro studies on HeLa cells show high uptake efficiency. Phototoxicity results give both irradiation time- and dosage-dependent cell death events. Because of the ease of incorporating other biomedical functional groups, we believe MSNs would be an ideal platform for biomedical applications. [source]

    Pivotal role of early B-cell factor 1 in development of striatonigral medium spiny neurons in the matrix compartment

    Mary Kay Lobo
    Abstract The mammalian striatum plays a critical function in motor control, motor and reward learning, and cognition. Dysfunction and degeneration of the striatal neurons are implicated in major neurological and psychiatric disorders. The vast majority of striatal neurons are medium spiny neurons (MSNs). MSNs can be further subdivided into distinct subtypes based on their physical localization in the striatal patch vs. matrix compartments and based on their axonal projections and marker gene expression (i.e., striatonigral MSNs vs. striatopallidal MSNs). Despite our extensive knowledge on the striatal cytoarchitecture and circuitry, little is known about the molecular mechanisms controlling the development of the MSN subtypes in the striatum. Early B-cell factor 1 (Ebf1) is a critical transcription factor implicated in striatal MSN development. One study shows that Ebf1 is critical for the differentiation of MSNs in the matrix, and our separate study demonstrates that Ebf1 is selectively expressed in the striatonigral MSNs and is essential for their postnatal differentiation. In the present study, we further validate the striatonigral MSN deficits in Ebf1,/, mice using multiple striatonigral MSN reporter mice. Moreover, we demonstrate that the striatonigral MSN deficits in these mice are restricted to those in the matrix, with relative sparing of those in the patch. Finally, we demonstrate that Ebf1 deficiency also results in reduced expression of another striatonigral-specific transcription factor, zinc finger binding protein 521 (Zfp521), which is a known Ebf1 functional partner. Overall, our study reveals that Ebf1 may play an essential role in controlling the differentiation of the striatonigral MSNs in the matrix compartment. © 2008 Wiley-Liss, Inc. [source]

    Quantitative analysis of pre- and postsynaptic sex differences in the nucleus accumbens

    Paul M. Forlano
    Abstract The nucleus accumbens (NAc) plays a central role in motivation and reward. While there is ample evidence for sex differences in addiction-related behaviors, little is known about the neuroanatomical substrates that underlie these sexual dimorphisms. We investigated sex differences in synaptic connectivity of the NAc by evaluating pre- and postsynaptic measures in gonadally intact male and proestrous female rats. We used DiI labeling and confocal microscopy to measure dendritic spine density, spine head size, dendritic length, and branching of medium spiny neurons (MSNs) in the NAc, and quantitative immunofluorescence to measure glutamatergic innervation using pre- (vesicular glutamate transporter 1 and 2) and postsynaptic (postsynaptic density 95) markers, as well as dopaminergic innervation of the NAc. We also utilized electron microscopy to complement the above measures. Clear but subtle sex differences were identified, namely, in distal dendritic spine density and the proportion of large spines on MSNs, both of which are greater in females. Sex differences in spine density and spine head size are evident in both the core and shell subregions, but are stronger in the core. This study is the first demonstration of neuroanatomical sex differences in the NAc and provides evidence that structural differences in synaptic connectivity and glutamatergic input may contribute to behavioral sex differences in reward and addiction. J. Comp. Neurol. 518:1330,1348, 2010. © 2009 Wiley-Liss, Inc. [source]

    Mesoporous Silica Nanosphere-Supported Chiral Ruthenium Catalysts: Synthesis, Characterization, and Asymmetric Hydrogenation Studies

    CHEMCATCHEM, Issue 3 2009
    Abstract Chiral RuCl2,diphosphine,diamine complexes with a pendant siloxy group were synthesized and characterized by NMR spectroscopy and mass spectrometry. The Ru complexes were grafted onto three different types of mesoporous silica nanospheres (MSNs) through the siloxane linkage, and the resulting MSN-supported Ru catalysts were highly active for the asymmetric hydrogenation of aromatic ketones, to afford chiral secondary alcohols, and racemic arylaldehydes, to give chiral primary alcohols. Excellent activities and enantioselectivities were observed for these MSN-supported Ru catalysts owing to readily accessible and uniform catalytic sites within the large channels of MSNs (diameters of >2,nm) and short diffusion lengths for the organic compounds as a result of small nanoparticle sizes of less than 1,,m. This catalyst immobilization strategy with MSN supports should be amenable to the design of many highly active and enantioselective heterogeneous asymmetric catalysts. [source]

    Structure analysis of triterpene saponins in Polygala tenuifolia by electrospray ionization ion trap multiple-stage mass spectrometry

    Jiangyun Liu
    Abstract Eighteen different triterpene saponins isolated from Polygala tenuifolia were investigated by electrospray ionization ion trap multiple-stage mass spectrometry (ESI-ITMSn) in positive and negative ion modes. MS1 -MS3/MS4 spectra of the both modes were analyzed, and they all gave fragments in line and shared common fragmentation patterns. Key fragments from MSn spectra of both the modes and their proposed fragmentation pathways were constructed with examples illustrated for the formation of characteristic fragments in the saponins. Two special fragmentation patterns were proposed: (1) the formation of fragments by cleavage of CH2O from ,12 -14,-CH2OH of the oleanene-type saponin aglycone in both positive and negative MSn (n , 2) modes; (2) the occurrence of fragments by cleavage of CO2 and 3-glucose as the characteristic structure feature of 23-COOH at the oleanene-type saponin aglycones coupled with 3-Glc substitutes in the negative MSn (n , 2) modes. Peak intensities in MSn spectra were also correlated with structural features and fragmentation preferences of the investigated saponins, which are discussed in detail. In general, fragments formed predominantly by cleavages of glycosidic bonds in the positive mode, while selective cleavages of acyl bonds preceded that of glycosidic bonds in negative MSn (n , 2) mode, both of which could well be applied to the structural analysis of these saponins. Interpretation of MSn spectra presented here provided diagnostic key fragment ions important for the structural elucidation of saponins in P.tenuifolia. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Automated software-guided identification of new buspirone metabolites using capillary LC coupled to ion trap and TOF mass spectrometry

    Anabel S. Fandiño
    Abstract The identification and structure elucidation of drug metabolites is one of the main objectives in in vitro ADME studies. Typical modern methodologies involve incubation of the drug with subcellular fractions to simulate metabolism followed by LC-MS/MS or LC-MSn analysis and chemometric approaches for the extraction of the metabolites. The objective of this work was the software-guided identification and structure elucidation of major and minor buspirone metabolites using capillary LC as a separation technique and ion trap MSn as well as electrospray ionization orthogonal acceleration time-of-flight (ESI oaTOF) mass spectrometry as detection techniques. Buspirone mainly underwent hydroxylation, dihydroxylation and N -oxidation in S9 fractions in the presence of phase I co-factors and the corresponding glucuronides were detected in the presence of phase II co-factors. The use of automated ion trap MS/MS data-dependent acquisition combined with a chemometric tool allowed the detection of five small chromatographic peaks of unexpected metabolites that co-eluted with the larger chromatographic peaks of expected metabolites. Using automatic assignment of ion trap MS/MS fragments as well as accurate mass measurements from an ESI oaTOF mass spectrometer, possible structures were postulated for these metabolites that were previously not reported in the literature. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Structure investigation of Maltacine C1a, C1b, C2a and C2b,cyclic peptide lactones of the Maltacine complex from Bacillus subtilis

    Gunnar Hagelin
    Abstract A new complex of cyclic peptide lactone antibiotics from Bacillus subtilis, which we named Maltacines, has recently been described. The structure elucidation of four of them is reported in this paper. The amino acid sequences and structures of the peptides were found by MSn of the ring-opened linear peptides, which gave uninterrupted sequences of Bn and Y,n ions. The identities of three unknown residues in the sequences were solved by a combination of derivatisation with phenylisothiocyanate (PITC), high-resolution mass spectrometry and H/D exchange. The nature and position of the cyclic structure was disclosed by a chemo-selective ring opening with Na18OH and was found to be a lactone formed between a hydroxyl of residue number 4 and the C -terminal amino acid number 12. For verification of the structure of the B2+ ion, peptides with different combinations of P/Q and P/K at the N -terminus were synthesised. The structure of the four peptides were found to be: C1a and C2a: cyclo-4,12(P-Q-Y-Adip-V-E-T-Y-Orn-103-Y-I-OH) and C1b/C2b: cyclo-4,12(P-Q-Y-Adip-V-E-T-Y-K-103-Y-I-OH). Adip = aminodihydroxy pentanoic acid. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Structure investigation of Maltacine D1a, D1b and D1c,cyclic peptide lactones of the Maltacine complex from Bacillus subtilis

    Gunnar Hagelin
    Abstract A new complex of cyclic peptide lactone antibiotics from Bacillus subtilis, which we named Maltacines has recently been described. The structure elucidation of three of them is reported in this paper. The amino acid sequences and structures of the peptides were found by MSn of the ring-opened linear peptides that gave uninterrupted sequences of Bn and Y,n ions. The identities of four unknown residues in the sequences were solved by a combination of derivatisation with phenylisothiocyanate (PITC), high-resolution mass spectrometry and H/D exchange. The nature and position of the cyclic structure was disclosed by a chemo-selective ring opening with Na18OH and was found to be a lactone formed between a hydroxyl of residue number 4 and the C -terminal amino acid number 12. For verification of the structure of the B2+ ion, peptides with different combinations of P/Q and P/K at the N -terminus were synthesized. The structures of the four peptides is tentatively suggested to be: D1a: cyclo(4,12)-P-Q-Y-Adip-A-E-T-Y-Orn-HGly-Y-I-OH, D1b: cyclo(4,12)-P-Q-Y-Adip-A-E-T-Y-Orn-S-Y-I-OH and D1c: cyclo(4,12)-P-Q-Y-Adip-A-E-T-Y-K-S-Y-I-OH. Adip = aminodihydroxy pentanoic acid and HGly = hydroxyglycine. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Novel benzyl rearrangements in electrospray ionization multistage tandem mass spectra of benzyl 2,,3, - didehydro-2,,3, -dideoxythymidin-5, -yl H-phosphonate

    Yi Chen
    Abstract Several alkyl 2,,3, -didehydro-2,,3, -dideoxythymidin-5, -yl H-phosphonates were synthesized and analyzed by electrospray ionization multistage tandem mass spectrometry (ESI , MSn). Two kinds of novel benzyl rearrangement reactions were observed in ESI , MS2 of [M + H]+, [M + Na]+ and [M + K]+ of benzyl 2,,3, -didehydro-2,,3, -dideoxythymidin-5, -yl H-phosphonate. Results from tandem mass spectrometry, high-resolution mass spectrometry and control experiments showed that the benzyl migration could undergo a four-membered cyclic rearrangement reaction, and benzyl was essential in the process. Copyright © 2004 John Wiley & Sons, Ltd. [source]

    Distinguishing N -oxide and hydroxyl compounds: impact of heated capillary/heated ion transfer tube in inducing atmospheric pressure ionization source decompositions

    Dilrukshi M. Peiris
    Abstract In the pharmaceutical industry, a higher attrition rate during the drug discovery process means a lower drug failure rate in the later stages. This translates into shorter drug development time and reduced cost for bringing a drug to market. Over the past few years, analytical strategies based on liquid chromatography/mass spectrometry (LC/MS) have gone through revolutionary changes and presently accommodate most of the needs of the pharmaceutical industry. Among these LC/MS techniques, collision induced dissociation (CID) or tandem mass spectrometry (MS/MS and MSn) techniques have been widely used to identify unknown compounds and characterize metabolites. MS/MS methods are generally ineffective for distinguishing isomeric compounds such as metabolites involving oxygenation of carbon or nitrogen atoms. Most recently, atmospheric pressure ionization (API) source decomposition methods have been shown to aid in the mass spectral distinction of isomeric oxygenated (N -oxide vs hydroxyl) products/metabolites. In previous studies, experiments were conducted using mass spectrometers equipped with a heated capillary interface between the mass analyzer and the ionization source. In the present study, we investigated the impact of the length of a heated capillary or heated ion transfer tube (a newer version of the heated capillary designed for accommodating orthogonal API source design) in inducing for-API source deoxygenation that allows the distinction of N -oxide from hydroxyl compounds. 8-Hydroxyquinoline (HO-Q), quinoline- N -oxide (Q-NO) and 8-hydroxyquinoline- N -oxide (HO-Q-NO) were used as model compounds on three different mass spectrometers (LCQ Deca, LCQ Advantage and TSQ Quantum). Irrespective of heated capillary or ion transfer tube length, N -oxides from this class of compounds underwent predominantly deoxygenation decomposition under atmospheric pressure chemical ionization conditions and the abundance of the diagnostic [M + H , O]+ ions increased with increasing vaporizer temperature. Furthermore, the results suggest that in API source decompostion methods described in this paper can be conducted using mass spectrometers with non-heated capillary or ion transfer tube API interfaces. Because N-oxides can undergo in-source decomposition and interfere with quantitation experiments, particular attention should be paid when developing API based bioanalytical methods. Copyright © 2004 John Wiley & Sons, Ltd. [source]

    Isomer separation of hyperbranched polyesteramides with gas-phase H/D exchange and a novel MSn approach: DoDIP

    Sander Koster
    Abstract Two approaches are introduced that provide information about the isomeric composition of hyperbranched polyesteramides. The first approach is based on a novel tandem mass spectrometric (MSn) approach that allows the study of different types of isomeric structures by a separation based on their difference in appearance energy. The method is called DoDIP: dissociation of depleted ion populations. A first MS/MS step is used to fragment isomers with relatively low appearance energy. The isomers with higher appearance energy are fragmented in a second MS/MS step of higher energy. The second approach is based on gas-phase H/D exchange experiments that result in a bimodal isotopic distribution for oligomers XnDn+1 of which one distribution corresponds to a type of isomeric structure that exhibits H/D exchange behaviour and the other to an isomeric structure that does not exhibit H/D exchange behaviour. X is a difunctional anhydride of phthalic acid (P), 1,2-cyclohexanedicarboxylic acid (C), succinic acid (S) or glutaric acid (G). D in XnDn+1 is a trifunctional diisopropanolamine and n the degree of polymerization. The type of isomeric structure that does not exhibit H/D exchange behaviour has a non-alternating monomer sequence that contains an amine bond with a relatively high proton affinity. The other isomeric structure that does exhibit H/D exchange behaviour has an alternating monomer sequence containing only amide and ester bonds with relatively low proton affinity. Oligomer structures were confirmed with additional MS2 experiments after H/D exchange. H/D exchange experiments on the fragments obtained after MS2 of the parent ion show that next to previously postulated mechanisms for the cleavage of the ester and amide bond another reaction pathway must be operational. A new mechanism is introduced to explain the H/D exchange behaviour of the fragments that requires a cleavage of the amide bonds only. Two types of fragments are formed by this mechanism. One type is protonated due to the cleavage of the amide bond whereas the other type has an oxazolonium ion structure due to the loss of an additional H2O. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Negative and positive ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and positive ion nano-electrospray ionization quadrupole ion trap mass spectrometry of peptidoglycan fragments isolated from various Bacillus species

    Gerold Bacher
    Abstract A general approach for the detailed characterization of sodium borohydride-reduced peptidoglycan fragments (syn. muropeptides), produced by muramidase digestion of the purified sacculus isolated from Bacillus subtilis (vegetative cell form of the wild type and a dacA mutant) and Bacillus megaterium (endospore form), is outlined based on UV matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and nano-electrospray ionization (nESI) quadrupole ion trap (QIT) mass spectrometry (MS). After enzymatic digestion and reduction of the resulting muropeptides, the complex glycopeptide mixture was separated and fractionated by reversed-phase high-performance liquid chromatography. Prior to mass spectrometric analysis, the muropeptide samples were subjected to a desalting step and an aliquot was taken for amino acid analysis. Initial molecular mass determination of these peptidoglycan fragments (ranging from monomeric to tetrameric muropeptides) was performed by positive and negative ion MALDI-MS using the thin-layer technique with the matrix ,-cyano-4-hydroxycinnamic acid. The results demonstrated that for the fast molecular mass determination of large sample numbers in the 0.8,10 pmol range and with a mass accuracy of ±0.07%, negative ion MALDI-MS in the linear TOF mode is the method of choice. After this kind of muropeptide screening often a detailed primary structural analysis is required owing to ambiguous data. Structural data could be obtained from peptidoglycan monomers by post-source decay (PSD) fragment ion analysis, but not from dimers or higher oligomers and not with the necessary sensitivity. Multistage collision-induced dissociation (CID) experiments performed on an nESI-QIT instrument were found to be the superior method for structural characterization of not only monomeric but also of dimeric and trimeric muropeptides. Up to MS4 experiments were sometimes necessary to obtain unambiguous structural information. Three examples are presented: (a) CID MSn (n = 2,4) of a peptidoglycan monomer (disaccharide-tripeptide) isolated from B. subtilis (wild type, vegetative cell form), (b) CID MSn (n = 2,4) of a peptidoglycan dimer (bis-disaccharide-tetrapentapeptide) obtained from a B. subtilis mutant (vegetative cell form) and (c) CID MS2 of a peptidoglycan trimer (a linear hexasaccharide with two peptide side chains) isolated from the spore cortex of B. megaterium. All MSn experiments were performed on singly charged precursor ions and the MS2 spectra were dominated by fragments derived from interglycosidic bond cleavages. MS3 and MS4 spectra exhibited mainly peptide moiety fragment ions. In case of the bis-disaccharide-tetrapentapeptide, the peptide branching point could be determined based on MS3 and MS4 spectra. The results demonstrate the utility of nESI-QIT-MS towards the facile determination of the glycan sequence, the peptide linkage and the peptide sequence and branching of purified muropeptides (monomeric up to trimeric forms). The wealth of structural information generated by nESI-QIT-MSn is unsurpassed by any other individual technique. Copyright © 2001 John Wiley & Sons, Ltd. [source]