Gas Phase Chemistry Of The 2-tert-butyl-3-phenylphosphirenylium Cation: Novel Onium Ions By Nucleophilic Attack At Phosphorus And De Novo P-spiro Bicyclic Phosphonium Ions Via [4 + 2+] Cycloaddition With Dienes

The 2-tert-butyl-3-phenylphosphirenylium ion 13 is formed in abundance in the gas phase from 1-chloro-1H-phosphirene 6 upon 70 eV electron ionization. Collision-induced dissociation (CID) and ion-molecule reactions followed by CID of the product ions were performed via pentaquadrupole mass spectrometry to probe the structure and reactivity of 13 towards representative nucleophiles and dienes. Under CID conditions, 13 produces a variety of fragment ions mainly via dissociation processes that are preceded by isomerizations. In ion-molecule reactions, 13 reacts readily with ethers, sulfides, pyridine and aniline to form hitherto unknown oxonium, sulfonium and azonium ions via nucleophilic attack at phosphorus. With butadiene, isoprene, 1-acetoxybutadiene, and with Danishefsky's diene (1-methoxy-3-silyloxybuta-1,3-diene), 13 undergoes [4 + 2+] cycloaddition at phosphorus to generate novel P-spiro bicyclic phosphonium ions. With butadiene and isoprene, a second [4 + 2] cycloaddition occurs which generates P-spiro tricyclic phosphonium ions. Whereas 13 also reacts readily with 1-acetoxybutadiene via [4 + 2+] cycloaddition, most of the nascent P-spiro cycloadducts are unstable and dissociate by the loss of either a neutral ketene or acetic acid molecule. B3LYP/6-31G(d,p) calculations were performed to gain insight into the structures of the product ions. The present study constitutes the first successful attempt to unravel the chemistry of 13, a unique 2π-Hückel phosphirenylium ion for which no direct solution chemical reactivity data are as yet available. The present findings also create a parallel with the solution reactivity of 1-halo-1H-phosphirenes and 1-triflato-1H-phosphirenes as precursors to phosphirenylium ions.12395400Laali, K.K., Geissler, B., Wagner, O., Hoffmann, J., Armbrust, R., Eisfeld, W., Regitz, M., (1994) J. Am. Chem. 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Sensory Evaluation Of Black Instant Coffee Beverage With Some Volatile Compounds Present In Aromatic Oil From Roasted Coffee [análise Sensorial De Bebida Preparada Com Café Instantâneo Com Alguns Compostos Voláteis Presentes No óleo Aromático De Café Torrado]

The oil obtained from Brazilian roasted coffee by supercritical CO2 extraction shows considerable aromatic properties, mainly composed by five aromatic compounds, 2-methylpyrazine; 2-furfurylalcohol, 2,5-dimethylpyrazine; γ-butyrolactone and 2-furfurylacetate. Sensory analyses were used to verify the influence of a mixture of these important classes of aromatic coffee compounds (pyrazines, furans and lactones) and of the roasted coffee aromatic oil on the coffee aroma and flavour of black instant freeze and spray-dried coffee beverages. In the acceptance evaluation of the aroma, the samples prepared with freeze-dried instant coffee without the mixture of volatile compounds (sample 4) were not significantly different from the freeze-dried instant coffee in which the aromatic coffee oil was added (sample 5) and from the sample prepared with freeze-dried coffee in which the mixture of the five volatile was added (sample 3), coincidentally from the same drying process. Therefore, sample (3) did not differ from samples prepared with spray dried instant coffee without (sample 1) and to which (sample 2) the mixture of volatile was added. Therefore, with respect to this attribute, the addition of this mixture did not interfere in this drink acceptance. Taking into consideration the flavor, samples prepared with freeze-dried instant coffee in which the aromatic coffee oil was added (5) and the samples with (3) and without (4) the mixture of the five volatile was added did not differ significantly, however sample (4) did not differ from samples (1) and (2). Regarding this attribute, the addition of the aromatic oil of roasted coffee or a mixture of volatile in samples of freeze-dried instant coffee had a better acceptance than those dried by spray dryer (1) and (2). Thus, the enrichment of drinks with the aromatic oil of roasted coffee, or even with the mixture of the five components did not influence the consumer acceptance with respect to the aroma, but exerts influence with respect to flavour.2917680Sarrazin, C., Representativeness of coffee aroma extracts: A comparision of different extraction methods (2000) Food Chemistry, 70 (1), pp. 99-106Ramos, E., Obtention of brewed coffee aroma extract by optimized supercritical CO2-based process (1998) Journal of Agricultural and Food Chemistry, 46 (10), pp. 4011-4016Oliveira, A.L., Sensory and yield response surface analysis of supercritical CO2 extracted aromatic oil from roasted coffee (2001) Journal of Food Science and Technology, 38 (1), pp. 38-42Nijssen, L.R., (1996) Volatile Compounds in Food, , The Netherlands, TNO-CIVOHolscher, W., Vitzthum, O.G., Steinhart, H., Phenyl alcohol - Source for Odorants in roasted coffee (1992) Journal of Agricultural and Food Chemistry, 40 (4), pp. 655-658Semmelroch, P., Grosch, W., Analysis of roasted coffee powders and brews by gas chromatography-olfactometry of headspace samples (1995) Lebensmittel-Wissenschaft und-Technologie, 28 (4), pp. 310-313Pollien, P., Krebsd, Y., Chaintreau, A., Comparison of a brew and an instant coffee using a new GC-Olfactrometric method (1997), 17. , INTERNATIONAL SCIENTIFIC COLOQUIUM ON COFFEE, Proceedings... Nairobi, Association Scientifique Internationale du CaféMayer, F., Czerny, M., Grosch, W., Sensory study of the character impact aroma compounds of coffee beverage (2000) European Food Research and Technology, 211 (4), pp. 272-276Semmelroch, P., Grosch, W., Studies on character impact odorants of coffee brews (1996) Journal of Agricultural and Food Chemistry, 44 (2), pp. 537-543Maeztu, L., Characterization of espresso coffee aroma by static headspace GC-MS and Sensory flavour profile (2001) Journal of Agricultural and Food Chemistry, 49 (11), pp. 5437-5444Elmore, J.S., Nursten, H.E., The effect of 2-furanmethanethiol upon the flavour of instant coffee (1993) International Journal of Food Science and Technology, 28 (5), pp. 531-536Blank, I., Grosch, W., On the role of (-)-2-methylisoborneol for the aroma of robusta coffee (2002) Journal of Agricultural and Food Chemistry, 50 (16), pp. 4653-4656Bassoli, D.G., Instant coffee with natural aroma by spray-drying (1993), 15, pp. 712-718. , In: INTERNATIONAL SCIENTIFIC COLOQUIUM ON COFFEE, 1993, Proceedings..., Montpellier: Association Scientifique Internationale du CaféCalviño, A.M., Zamora, M.C., Sarchi, M.I., Principal components and cluster analysis for descriptive sensory assessment of instant coffee (1996) Journal of Sensory Studies, 11 (3), pp. 191-210Zamora, M.C., Calvino, A.M., A comparison of methodology applied to the selection of a panel for sensory evaluation of instant coffee (1996) Journal of Sensory Studies, 11 (3), pp. 211-226Jong, S., Heidema, J., van der Knaap, C.M., Generalized procrusters analysis of coffee brands tested by five european sensory panels (1998) Food Quality and Preference, 9 (3), pp. 111-114Oliveira, A.L., Cabral, F.A., Eberlin, M.N., Prediction of solubility of some compounds of roasted coffee aromatic oil in supercritical CO2 (2003), In: INTERNATIONAL SYMPOSIUM ON SUPERCRITICAL FLUIDS, Proceedings..., Versailles: International Society for Advancement of Supercritical FluidsWang, T.H., Shanfield, H., Zlatkis, A., Analysis of trace volatile organic compounds in coffee by headspace concentration and gas chromatography-mass spectrometry (1983) Chromatographia, 17 (8), pp. 411-417Hashim, L., Chaveron, H., Use of methylpyrazine ratios to monitor the coffee roasting (1996) Food Research International, 28 (6), pp. 619-623Roberts, D.D., Pollien, P., Milo, C., Solid-phase microextraction method development for headspace analysis of volatile flavour compounds (2000) Journal of Agricultural and Food Chemistry, 48 (6), pp. 2430-2437Rivetti, D., Effect of water composition and water treatment on expresso coffee percolation (2001), In: INTERNATIONAL SCIENTIFIC COLOQUIUM ON COFFEE, Proceedings... Trieste: Association Scientifique Internationale du CaféMeilgaard, M., Civille, G.V., Carr, B.T., (1987) Sensory Evaluation Techiniques, , Boca Raton: CRC PressStone, H., Sidel, J.L., (1993) Sensory Evaluation Practices, , London: Academic PressSteel, R.G.D., Torrie, J.H., (1980) Principles and Procedures of Statistics - A Biometrical Approach, , Singapura: McGraw-Hil

tri-n-butyltin hydride-mediated radical reaction of a 2-iodobenzamide: Formation of an unexpected carbon-tin bond

Leonardo S. Santos. Instituto de Química de Recursos Naturales, Universidad de Talca, P.O. Box 747, Talca - Chile.The tri-n-butyltin hydride-mediated reaction of methyl 2,3-di-O-benzyl-4-O-trans-cinnamyl -6-deoxy-6-(2-iodobenzoylamino)-a-D-galactopyranoside afforded an unexpected aryltributyltin compound. The structure of this new tetraorganotin(IV) product has been elucidated by 1H, 13C NMR spectroscopy, COSY and HMQC experiments and electrospray ionization mass spectrometry (ESI-MS). The formation of this new compound via a radical coupling reaction and a radical addition-elimination process is discusse

Fingerprinting of propolis by easy ambient sonic-spray ionization mass spectrometry

Chemical profiles of a representative set of 49 propolis ethanolic extracts collected worldwide (North and South America, Europe, Asia and Oceania) were obtained via easy ambient sonic-spray ionization mass spectrometry (EASI-MS). This simple and easily implemented fingerprinting technique analyses directly (without any pre-separation or sample manipulation) a tiny droplet of the ethanolic extract placed on a inert surface under ambient conditions. Data acquisition took about a minute per sample with no substantial sample carry-over. Extraction of propolis with ethanol by using an ultrasonic bath method gave EASI-MS data similar to the traditional maceration method, reducing total analysis time for the crude propolis resin from a week to just ca 1 h. Principal component analysis of the EASI-MS data is shown to group samples according to the plant sources of their resins, which characterizes their geographical origin. © 2009 Elsevier B.V. All rights reserved

Validation of a rapid analytical method by HPLC for determining coumarin in guaco (Mikania glomerata Sprengel) confirmed with mass spectrometry

The species Mikania glomerata Sprengel, popularly known in Brazil as guaco , is widely used as an expectorant to treat respiratory diseases. Its pharmacological activity is mainly attributed to coumarin. The results showed that the method for determining coumarin presented linearity from 0.05 to 0.8 mg mL-1. It was considered selective, accurate, and precise according to the specific resolution from ANVISA, the Brazilian regulatory agency. The proposal of a rapid method for the determining coumarin in extracts of guaco is interesting for routine industrial quality control in order to obtain standardized, efficient, and safe phytotherapic medicines.A espécie Mikania glomerata Sprengel, popularmente conhecida no Brasil como guaco, é amplamente utilizada como expectorante para tratar doenças respiratórias e tem a sua atividade farmacológica atribuída principalmente a cumarina. Os resultados mostraram que o método apresenta linearidade de 0,05 a 0,8 mg mL-1. Ele foi considerado seletivo, exato e preciso. A proposta de um método rápido para determinação de cumarina em extratos de guaco torna-se interessante para a rotina de controle de qualidade industrial, visando à obtenção de medicamentos fitoterápicos padronizados.A espécie Mikania glomerata Sprengel, popularmente conhecida no Brasil como guaco, é amplamente utilizada como expectorante para tratar doenças respiratórias e tem a sua atividade farmacológica atribuída principalmente a cumarina. Os resultados mostraram1811316325The species Mikania glomerata Sprengel, popularly known in Brazil as “guaco”, is widely used as an expectorant to treat respiratory diseases. Its pharmacological activity is mainly attributed to coumarin. The results showed that the method for determinin

Lipidomic profile as a non-invasive tool to predict endometrial receptivity in freeze-all cycles

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19-base Pair Deletion Polymorphism Of The Dihydrofolate Reductase (dhfr) Gene: Maternal Risk Of Down Syndrome And Folate Metabolism [polimorfismo De Deleção De 19 Pares De Bases Do Gene Dihidrofolato Redutase (dhfr): Risco Materno Para Síndrome De Down E Metabolismo Do Folato]

Context and objective: Polymorphisms in genes involved in folate metabolism may modulate the maternal risk of Down syndrome (DS). This study evaluated the influence of a 19-base pair (bp) deletion polymorphism in intron-1 of the dihydrofolate reductase (DHFR) gene on the maternal risk of DS, and investigated the association between this polymorphism and variations in the concentrations of serum folate and plasma homocysteine (Hcy) and plasma methylmalonic acid (MMA). Design and setting: Analytical cross-sectional study carried out at Faculdade de Medicina de São José do Rio Preto (Famerp). Methods: 105 mothers of individuals with free trisomy of chromosome 21, and 184 control mothers were evaluated. Molecular analysis on the polymorphism was performed using the polymerase chain reaction (PCR) through differences in the sizes of fragments. Folate was quantified by means of chemiluminescence, and Hcy and MMA by means of liquid chromatography and sequential mass spectrometry. Results: There was no difference between the groups in relation to allele and genotype frequencies (P = 0.44; P = 0.69, respectively). The folate, Hcy and MMA concentrations did not differ significantly between the groups, in relation to genotypes (P > 0.05). Conclusions: The 19-bp deletion polymorphism of DHFR gene was not a maternal risk factor for DS and was not related to variations in the concentrations of serum folate and plasma Hcy and MMA in the study population.1284215218Freeman, S.B., Allen, E.G., Oxford-Wright, C.L., The National Down Syndrome Project: Design and implementation (2007) Public Health Rep, 122 (1), pp. 62-72Ramírez, N.J., Belalcázar, H.M., Yunis, J.J., Parental origin, nondisjunction, and recombination of the extra chromosome 21 in Down syndrome: A study in a sample of the Colombian population (2007) Biomedica, 27 (1), pp. 141-148James, S.J., Pogribna, M., Pogribny, I.P., Abnormal folate metabolism and mutation in the methylenetetrahydrofolate reductase gene may be maternal risk factors for Down syndrome (1999) Am J Clin Nutr, 70 (4), pp. 495-501Patterson, D., Folate metabolism and the risk of Down syndrome (2008) Downs Syndr Res Pract, 12 (2), pp. 93-97Biselli, J.M., Goloni-Bertollo, E.M., Zampieri, B.L., Genetic polymorphisms involved in folate metabolism and elevated plasma concentrations of homocysteine: Maternal risk factors for Down syndrome in Brazil (2008) Genet Mol Res, 7 (1), pp. 33-42Meguid, N.A., Dardir, A.A., Khass, M., MTHFR genetic polymorphism as a risk factor in Egyptian mothers with Down syndrome children (2008) Dis Markers, 24 (1), pp. 19-26Coppedè, F., Migheli, F., Bargagna, S., Association of maternal polymorphisms in folate metabolizing genes with chromosome damage and risk of Down syndrome offspring (2009) Neurosci Lett, 449 (1), pp. 15-19Pozzi, E., Vergani, P., Dalprà, L., Maternal polymorphisms for methyltetrahydrofolate reductase and methionine synthetase reductase and risk of children with Down syndrome (2009) Am J Obstet Gynecol, 200 (6), pp. 636e1-636e6Stanislawska-Sachadyn, A., Brown, K.S., Mitchell, L.E., An insertion/deletion polymorphism of the dihydrofolate reductase (DHFR) gene is associated with serum and red blood cell folate concentrations in women (2008) Hum Genet, 123 (3), pp. 289-295Johnson, W.G., Stenroos, E.S., Spychala, J.R., New 19 bp deletion polymorphism in intron-1 of dihydrofolate reductase (DHFR): A risk factor for spina bifida acting in mothers during pregnancy? (2004) Am J Med Genet A, 124 A (4), pp. 339-345Parle-McDermott, A., Pangilinan, F., Mills, J.L., The 19-bp deletion polymorphism in intron-1 of dihydrofolate reductase (DHFR) may decrease rather than increase risk for spina bifida in the Irish population (2007) Am J Med Genet A, 143 A (11), pp. 1174-1180Xu, X., Gammon, M.D., Wetmur, J.G., A functional 19-base pair deletion polymorphism of dihydrofolate reductase (DHFR) and risk of breast cancer in multivitamin users (2007) Am J Clin Nutr, 85 (4), pp. 1098-1102Gellekink, H., Blom, H.J., van der Linden, I.J., den Heijer, M., Molecular genetic analysis of the human dihydrofolate reductase gene: Relation with plasma total homocysteine, serum and red blood cell folate levels (2007) Eur J Hum Genet, 15 (1), pp. 103-109Miller, S.A., Dykes, D.D., Polesky, H.F., A simple salting out procedure for extracting DNA from human nucleated cells (1988) Nucleic Acids Res, 16 (3), p. 1215Dulucq, S., St-Onge, G., Gagné, V., DNA variants in the dihydrofolate reductase gene and outcome in childhood ALL (2008) Blood, 111 (7), pp. 3692-3700Haddad, R., Mendes, M.A., Höehr, N.F., Eberlin, M.N., Amino acid quantitation in aqueous matrices via trap and release membrane introduction mass spectrometry: Homocysteine in human plasma (2001) Analyst, 126 (8), pp. 1212-1215de Andrade, C.R., Fukada, S.Y., Olivon, V.C., Alpha1D-adrenoceptor-induced relaxation on rat carotid artery is impaired during the endothelial dysfunction evoked in the early stages of hyperhomocysteinemia (2006) Eur J Pharmacol, 543 (1-3), pp. 83-91Carvalho, V.M., Kok, F., Determination of serum methylmalonic acid by alkylative extraction and liquid chromatography coupled to tandem mass spectrometry (2008) Anal Biochem, 381 (1), pp. 67-73Fenech, M., The role of folic acid and Vitamin B12 in genomic stability of human cells (2001) Mutat Res, 475 (1-2), pp. 57-67Wang, X., Thomas, P., Xue, J., Fenech, M., Folate deficiency induces aneuploidy in human lymphocytes in vitro-evidence using cytokinesis-blocked cells and probes specific for chromosomes 17 and 21 (2004) Mutat Res, 551 (1-2), pp. 167-180Beetstra, S., Thomas, P., Salisbury, C., Turner, J., Fenech, M., Folic acid deficiency increases chromosomal instability, chromosome 21 aneuploidy and sensitivity to radiation-induced micronuclei (2005) Mutat Res, 578 (1-2), pp. 317-326Finkelstein, J.D., Martin, J.J., Homocysteine (2000) Int J Biochem Cell Biol, 32 (4), pp. 385-389Coppedè, F., Marini, G., Bargagna, S., Folate gene polymorphisms and the risk of Down syndrome pregnancies in young Italian women (2006) Am J Med Genet A, 140 (10), pp. 1083-1091Wang, S.S., Qiao, F.Y., Feng, L., Lv, J.J., Polymorphisms in genes involved in folate metabolism as maternal risk factors for Down syndrome in China (2008) J Zhejiang Univ Sci B, 9 (2), pp. 93-99Kalmbach, R.D., Choumenkovitch, S.F., Troen, A.P., A 19-base pair deletion polymorphism in dihydrofolate reductase is associated with increased unmetabolized folic acid in plasma and decreased red blood cell folate (2008) J Nutr, 138 (12), pp. 2323-2327van der Linden, I.J., Nguyen, U., Heil, S.G., Variation and expression of dihydrofolate reductase (DHFR) in relation to spina bifida (2007) Mol Genet Metab, 91 (1), pp. 98-103Barkai, G., Arbuzova, S., Berkenstadt, M., Heifetz, S., Cuckle, H., Frequency of Down's syndrome and neural tube defects in the same family (2003) Lancet, 361 (9366), pp. 1331-1335Guéant, J.L., Guéant-Rodriguez, R.M., Anello, G., Genetic determinants of folate and vitamin B12 metabolism: A common pathway in neural tube defect and Down syndrome? (2003) Clin Chem Lab Med, 41 (11), pp. 1473-1477Klee, G.G., Cobalamin and folate evaluation: Measurement of methylmalonic acid and homocysteine vs vitamin B(12) and folate (2000) Clin Chem, 46 (8 PART 2), pp. 1277-1283Galloway, M., Rushworth, L., Red cell or serum folate? Results from the National Pathology Alliance benchmarking review (2003) J Clin Pathol, 56 (12), pp. 924-926Bunduki, V., Dommergues, M., Zittoun, J., Maternal-fetal folate status and neural tube defects: A case control study (1995) Biol Neonate, 67 (3), pp. 154-159Kilbride, J., Baker, T.G., Parapia, L.A., Khoury, S.A., Iron status, serum folate and B(12) values in pregnancy and postpartum: Report from a study in Jordan (2000) Ann Saudi Med, 20 (5-6), pp. 371-376Zhang, T., Xin, R., Gu, X., Maternal serum vitamin B12, folate and homocysteine and the risk of neural tube defects in the offspring in a high-risk area of China (2009) Public Health Nutr, 12 (5), pp. 680-686Eser, B., Cosar, M., Eser, O., 677C>T and 1298A>C polymorphisms of methylenetetrahydropholate reductase gene and biochemical parameters in Turkish population with spina bifida occulta (2010) Turk Neurosurg, 20 (1), pp. 9-1

Gas-phase Polar Cycloadditions

The dilute gas-phase environment of mass spectrometers provides versatile and convenient medium in which chemists can form a great variety of ionic species and study their intrinsic reactivity exploring reaction mechanisms and screening for new reactions and their applications. Recent and illustrative examples of gas-phase polar cycloadditions of even and odd-electrons ions, which have been observed (some for the first time) in the solvent- and counter ion-free environment of mass spectrometers, are presented. Synthetic and analytical applications of such reactions and correlations with analogous reactions observed in solution are also discussed. © 2004 Elsevier B.V. All rights reserved.2353263278Carruthers, W., Cycloadditon Reactions in Organic Synthesis, p. 1990. , PergamonDiels, O., Alder, K., (1928) Justus Liebigs Ann. Chem., 460, p. 98(1997) IUPAC Compendium of Chemical Terminology, Second Ed.Schmidt, R.R., (1973) Angew. Chem. Int. 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[No abstract available]1

Functional Group Selective Ion-molecule Reactions

The mechanistic details and potential applications of ion-molecule reactions were studied. Gas phase ion-molecule reactions was placed at the center of attention in mass spectrometry. The combination of conventional and new ionization and multiple-stage mass spectrometry techniques provide access for mass spectrometrists to a world of gaseous ions, reaction environments, and ion characterization methods. Functional group selective ion-molecule reactions will certainly found increasing applications in a variety of fields.1314Staley, R.H., Corderman, R.R., Foster, M.S., Beauchamp, J.L., (1974) J. Am. Chem. Soc., 96, p. 1260Moraes, L.A.B., Eberlin, M.N., (2000) Chem. Eur. J., 6, p. 897Kenttamaa, H.I., Cooks, R.G., (1989) J. Am. Chem. Soc., 111, p. 4122Moraes, L.A.B., Eberlin, M.N., (2002) J. Mass Spectrom., 37, p. 162Eberlin, M.N., Cooks, R.G., (1993) J. Am. Chem. Soc., 115, p. 9226Meurer, E.C., Eberlin, M.N., (2001) Int. J. Mass Spectrom., 210-211, p. 469Carvalho, M., Gozzo, F.C., Mendes, M.A., Sparrapan, R., Kascheres, C., Eberlin, M.N., (1998) Chem. Eur. J., 4, p. 1161Moraes, L.A.B., Eberlin, M.N., (1996) J. Org. Chem., 61, p. 8726Moraes, L.A.B., Gozzo, F.C., Eberlin, M.N., (1997) J. Org. Chem., 62, p. 5096H. Chen, X. Zheng, R. G. Cooks, unpublished resultsEberlin, M.N., Cooks, R.G., (1993) Org. Mass Spectrom., 28, p. 679Thompson, R.S., Guler, L.P., Nelson, E.D., Yu, Y.-Q., Kenttamaa, H.L., J. Org. Chem., , in pressStirk, K.M., Orlowski, J.C., Leeck, D.T., Kenttamaa, H.I., (1992) J. Am. Chem. Soc., 114, p. 8604Ramos, L.E., Cardoso, A.M., Ferrer Correia, A.J., Nibbering, N.M.M., (2000) Int. J. Mass Spectrom., 203, p. 101Kempen, E.C., Brodbelt, J., (1997) J. Mass Spectrom., 32, p. 846O'Hair, R.A.J., Reid, G.E., (2000) J. Am. Soc. Mass Spectrom., 111, p. 244Reid, G.E., Tichy, S.E., Pérez, J., O'Hair, R.A.J., Simpson, R.J., Kenttamaa, H.I., (2001) J. Am. Chem. Soc., 123, p. 1184Cooks, R.G., (2002) 50th Annual Conference on Mass Spectrometry and Allied Topics, , Monday Plenary Lecture, Orlando, Jun