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  • 1
    Publication Date: 2015-09-15
    Description: The extent to which low-frequency (minor allele frequency (MAF) between 1-5%) and rare (MAF 〈/= 1%) variants contribute to complex traits and disease in the general population is mainly unknown. Bone mineral density (BMD) is highly heritable, a major predictor of osteoporotic fractures, and has been previously associated with common genetic variants, as well as rare, population-specific, coding variants. Here we identify novel non-coding genetic variants with large effects on BMD (ntotal = 53,236) and fracture (ntotal = 508,253) in individuals of European ancestry from the general population. Associations for BMD were derived from whole-genome sequencing (n = 2,882 from UK10K (ref. 10); a population-based genome sequencing consortium), whole-exome sequencing (n = 3,549), deep imputation of genotyped samples using a combined UK10K/1000 Genomes reference panel (n = 26,534), and de novo replication genotyping (n = 20,271). We identified a low-frequency non-coding variant near a novel locus, EN1, with an effect size fourfold larger than the mean of previously reported common variants for lumbar spine BMD (rs11692564(T), MAF = 1.6%, replication effect size = +0.20 s.d., Pmeta = 2 x 10(-14)), which was also associated with a decreased risk of fracture (odds ratio = 0.85; P = 2 x 10(-11); ncases = 98,742 and ncontrols = 409,511). Using an En1(cre/flox) mouse model, we observed that conditional loss of En1 results in low bone mass, probably as a consequence of high bone turnover. We also identified a novel low-frequency non-coding variant with large effects on BMD near WNT16 (rs148771817(T), MAF = 1.2%, replication effect size = +0.41 s.d., Pmeta = 1 x 10(-11)). In general, there was an excess of association signals arising from deleterious coding and conserved non-coding variants. These findings provide evidence that low-frequency non-coding variants have large effects on BMD and fracture, thereby providing rationale for whole-genome sequencing and improved imputation reference panels to study the genetic architecture of complex traits and disease in the general population.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4755714/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4755714/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zheng, Hou-Feng -- Forgetta, Vincenzo -- Hsu, Yi-Hsiang -- Estrada, Karol -- Rosello-Diez, Alberto -- Leo, Paul J -- Dahia, Chitra L -- Park-Min, Kyung Hyun -- Tobias, Jonathan H -- Kooperberg, Charles -- Kleinman, Aaron -- Styrkarsdottir, Unnur -- Liu, Ching-Ti -- Uggla, Charlotta -- Evans, Daniel S -- Nielson, Carrie M -- Walter, Klaudia -- Pettersson-Kymmer, Ulrika -- McCarthy, Shane -- Eriksson, Joel -- Kwan, Tony -- Jhamai, Mila -- Trajanoska, Katerina -- Memari, Yasin -- Min, Josine -- Huang, Jie -- Danecek, Petr -- Wilmot, Beth -- Li, Rui -- Chou, Wen-Chi -- Mokry, Lauren E -- Moayyeri, Alireza -- Claussnitzer, Melina -- Cheng, Chia-Ho -- Cheung, Warren -- Medina-Gomez, Carolina -- Ge, Bing -- Chen, Shu-Huang -- Choi, Kwangbom -- Oei, Ling -- Fraser, James -- Kraaij, Robert -- Hibbs, Matthew A -- Gregson, Celia L -- Paquette, Denis -- Hofman, Albert -- Wibom, Carl -- Tranah, Gregory J -- Marshall, Mhairi -- Gardiner, Brooke B -- Cremin, Katie -- Auer, Paul -- Hsu, Li -- Ring, Sue -- Tung, Joyce Y -- Thorleifsson, Gudmar -- Enneman, Anke W -- van Schoor, Natasja M -- de Groot, Lisette C P G M -- van der Velde, Nathalie -- Melin, Beatrice -- Kemp, John P -- Christiansen, Claus -- Sayers, Adrian -- Zhou, Yanhua -- Calderari, Sophie -- van Rooij, Jeroen -- Carlson, Chris -- Peters, Ulrike -- Berlivet, Soizik -- Dostie, Josee -- Uitterlinden, Andre G -- Williams, Stephen R -- Farber, Charles -- Grinberg, Daniel -- LaCroix, Andrea Z -- Haessler, Jeff -- Chasman, Daniel I -- Giulianini, Franco -- Rose, Lynda M -- Ridker, Paul M -- Eisman, John A -- Nguyen, Tuan V -- Center, Jacqueline R -- Nogues, Xavier -- Garcia-Giralt, Natalia -- Launer, Lenore L -- Gudnason, Vilmunder -- Mellstrom, Dan -- Vandenput, Liesbeth -- Amin, Najaf -- van Duijn, Cornelia M -- Karlsson, Magnus K -- Ljunggren, Osten -- Svensson, Olle -- Hallmans, Goran -- Rousseau, Francois -- Giroux, Sylvie -- Bussiere, Johanne -- Arp, Pascal P -- Koromani, Fjorda -- Prince, Richard L -- Lewis, Joshua R -- Langdahl, Bente L -- Hermann, A Pernille -- Jensen, Jens-Erik B -- Kaptoge, Stephen -- Khaw, Kay-Tee -- Reeve, Jonathan -- Formosa, Melissa M -- Xuereb-Anastasi, Angela -- Akesson, Kristina -- McGuigan, Fiona E -- Garg, Gaurav -- Olmos, Jose M -- Zarrabeitia, Maria T -- Riancho, Jose A -- Ralston, Stuart H -- Alonso, Nerea -- Jiang, Xi -- Goltzman, David -- Pastinen, Tomi -- Grundberg, Elin -- Gauguier, Dominique -- Orwoll, Eric S -- Karasik, David -- Davey-Smith, George -- AOGC Consortium -- Smith, Albert V -- Siggeirsdottir, Kristin -- Harris, Tamara B -- Zillikens, M Carola -- van Meurs, Joyce B J -- Thorsteinsdottir, Unnur -- Maurano, Matthew T -- Timpson, Nicholas J -- Soranzo, Nicole -- Durbin, Richard -- Wilson, Scott G -- Ntzani, Evangelia E -- Brown, Matthew A -- Stefansson, Kari -- Hinds, David A -- Spector, Tim -- Cupples, L Adrienne -- Ohlsson, Claes -- Greenwood, Celia M T -- UK10K Consortium -- Jackson, Rebecca D -- Rowe, David W -- Loomis, Cynthia A -- Evans, David M -- Ackert-Bicknell, Cheryl L -- Joyner, Alexandra L -- Duncan, Emma L -- Kiel, Douglas P -- Rivadeneira, Fernando -- Richards, J Brent -- G1000143/Medical Research Council/United Kingdom -- K01 AR062655/AR/NIAMS NIH HHS/ -- MC_UU_12013/3/Medical Research Council/United Kingdom -- R01 AG005394/AG/NIA NIH HHS/ -- R01 AG005407/AG/NIA NIH HHS/ -- R01 AG027574/AG/NIA NIH HHS/ -- R01 AG027576/AG/NIA NIH HHS/ -- R01 AR035582/AR/NIAMS NIH HHS/ -- R01 AR035583/AR/NIAMS NIH HHS/ -- RC2 AR058973/AR/NIAMS NIH HHS/ -- U01 AG018197/AG/NIA NIH HHS/ -- U01 AG042140/AG/NIA NIH HHS/ -- U01 AG042143/AG/NIA NIH HHS/ -- U01 AR045580/AR/NIAMS NIH HHS/ -- U01 AR045583/AR/NIAMS NIH HHS/ -- U01 AR045614/AR/NIAMS NIH HHS/ -- U01 AR045632/AR/NIAMS NIH HHS/ -- U01 AR045647/AR/NIAMS NIH HHS/ -- U01 AR045654/AR/NIAMS NIH HHS/ -- U01 AR066160/AR/NIAMS NIH HHS/ -- England -- Nature. 2015 Oct 1;526(7571):112-7. doi: 10.1038/nature14878. Epub 2015 Sep 14.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Departments of Medicine, Human Genetics, Epidemiology and Biostatistics, McGill University, Montreal H3A 1A2, Canada. ; Department of Medicine, Lady Davis Institute for Medical Research, Jewish General Hospital, McGill University, Montreal H3T 1E2, Canada. ; Institute for Aging Research, Hebrew SeniorLife, Boston, Massachusetts 02131, USA. ; Department of Medicine, Harvard Medical School, Boston, Massachusetts 02115, USA. ; Broad Institute of MIT and Harvard, Boston, Massachusetts 02115, USA. ; Department of Internal Medicine, Erasmus Medical Center, Rotterdam 3015GE, The Netherlands. ; Analytic and Translational Genetics Unit, Massachusetts General Hospital, Boston, Massachusetts 02114, USA. ; Developmental Biology Program, Sloan Kettering Institute, New York, New York 10065, USA. ; The University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, Brisbane 4102, Australia. ; Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, New York 10065, USA. ; Tissue Engineering, Regeneration and Repair Program, Hospital for Special Surgery, New York 10021, USA. ; Rheumatology Divison, Hospital for Special Surgery New York, New York 10021, USA. ; School of Clinical Science, University of Bristol, Bristol BS10 5NB, UK. ; MRC Integrative Epidemiology Unit, University of Bristol, Bristol BS8 2BN, UK. ; Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA. ; Department of Research, 23andMe, Mountain View, California 94041, USA. ; Department of Population Genomics, deCODE Genetics, Reykjavik IS-101, Iceland. ; Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts 02118, USA. ; Centre for Bone and Arthritis Research, Department of Internal Medicine and Clinical Nutrition, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg S-413 45, Sweden. ; California Pacific Medical Center Research Institute, San Francisco, California 94158, USA. ; Department of Public Health and Preventive Medicine, Oregon Health &Science University, Portland, Oregon 97239, USA. ; Bone &Mineral Unit, Oregon Health &Science University, Portland, Oregon 97239, USA. ; Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge CB10 1SA, UK. ; Departments of Pharmacology and Clinical Neurosciences, Umea University, Umea S-901 87, Sweden. ; Department of Public Health and Clinical Medicine, Umea University, Umea SE-901 87, Sweden. ; Centre for Bone and Arthritis Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg S-413 45, Sweden. ; McGill University and Genome Quebec Innovation Centre, Montreal H3A 0G1, Canada. ; Department of Epidemiology, Erasmus Medical Center, Rotterdam 3015GE, The Netherlands. ; Oregon Clinical and Translational Research Institute, Oregon Health &Science University, Portland, Oregon 97239, USA. ; Department of Medical and Clinical Informatics, Oregon Health &Science University, Portland, Oregon 97239, USA. ; Farr Institute of Health Informatics Research, University College London, London NW1 2DA, UK. ; Department of Twin Research and Genetic Epidemiology, King's College London, London SE1 7EH, UK. ; Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02115, USA. ; Department of Human Genetics, McGill University, Montreal H3A 1B1, Canada. ; Netherlands Genomics Initiative (NGI)-sponsored Netherlands Consortium for Healthy Aging (NCHA), Leiden 2300RC, The Netherlands. ; Center for Musculoskeletal Research, University of Rochester, Rochester, New York 14642, USA. ; Department of Biochemistry and Goodman Cancer Research Center, McGill University, Montreal H3G 1Y6, Canada. ; Department of Computer Science, Trinity University, San Antonio, Texas 78212, USA. ; Musculoskeletal Research Unit, University of Bristol, Bristol BS10 5NB, UK. ; Department of Radiation Sciences, Umea University, Umea S-901 87, Sweden. ; School of Public Health, University of Wisconsin, Milwaukee, Wisconsin 53726, USA. ; School of Social and Community Medicine, University of Bristol, Bristol BS8 2BN, UK. ; Department of Statistics, deCODE Genetics, Reykjavik IS-101, Iceland. ; Department of Epidemiology and Biostatistics and the EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam 1007 MB, The Netherlands. ; Department of Human Nutrition, Wageningen University, Wageningen 6700 EV, The Netherlands. ; Department of Internal Medicine, Section Geriatrics, Academic Medical Center, Amsterdam 1105, The Netherlands. ; Nordic Bioscience, Herlev 2730, Denmark. ; Cordeliers Research Centre, INSERM UMRS 1138, Paris 75006, France. ; Institute of Cardiometabolism and Nutrition, University Pierre &Marie Curie, Paris 75013, France. ; Departments of Medicine (Cardiovascular Medicine), Centre for Public Health Genomics, University of Virginia, Charlottesville, Virginia 22908, USA. ; Department of Genetics, University of Barcelona, Barcelona 08028, Spain. ; U-720, Centre for Biomedical Network Research on Rare Diseases (CIBERER), Barcelona 28029, Spain. ; Department of Human Molecular Genetics, The Institute of Biomedicine of the University of Barcelona (IBUB), Barcelona 08028, Spain. ; Women's Health Center of Excellence Family Medicine and Public Health, University of California - San Diego, San Diego, California 92093, USA. ; Division of Preventive Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02215, USA. ; Osteoporosis &Bone Biology Program, Garvan Institute of Medical Research, Sydney 2010, Australia. ; School of Medicine Sydney, University of Notre Dame Australia, Sydney 6959, Australia. ; St. Vincent's Hospital &Clinical School, NSW University, Sydney 2010, Australia. ; Musculoskeletal Research Group, Institut Hospital del Mar d'Investigacions Mediques, Barcelona 08003, Spain. ; Cooperative Research Network on Aging and Fragility (RETICEF), Institute of Health Carlos III, 28029, Spain. ; Department of Internal Medicine, Hospital del Mar, Universitat Autonoma de Barcelona, Barcelona 08193, Spain. ; Neuroepidemiology Section, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892, USA. ; Icelandic Heart Association, Kopavogur IS-201, Iceland. ; Faculty of Medicine, University of Iceland, Reykjavik IS-101, Iceland. ; Genetic epidemiology unit, Department of Epidemiology, Erasmus MC, Rotterdam 3000CA, The Netherlands. ; Department of Orthopaedics, Skane University Hospital Malmo 205 02, Sweden. ; Department of Medical Sciences, University of Uppsala, Uppsala 751 85, Sweden. ; Department of Surgical and Perioperative Sciences, Umea Unviersity, Umea 901 85, Sweden. ; Department of Molecular Biology, Medical Biochemistry and Pathology, Universite Laval, Quebec City G1V 0A6, Canada. ; Axe Sante des Populations et Pratiques Optimales en Sante, Centre de recherche du CHU de Quebec, Quebec City G1V 4G2, Canada. ; Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands 6009, Australia. ; Department of Medicine, University of Western Australia, Perth 6009, Australia. ; Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus C 8000, Denmark. ; Department of Endocrinology, Odense University Hospital, Odense C 5000, Denmark. ; Department of Endocrinology, Hvidovre University Hospital, Hvidovre 2650, Denmark. ; Clinical Gerontology Unit, University of Cambridge, Cambridge CB2 2QQ, UK. ; Medicine and Public Health and Primary Care, University of Cambridge, Cambridge CB1 8RN, UK. ; Institute of Musculoskeletal Sciences, The Botnar Research Centre, University of Oxford, Oxford OX3 7LD, UK. ; Department of Applied Biomedical Science, Faculty of Health Sciences, University of Malta, Msida MSD 2080, Malta. ; Clinical and Molecular Osteoporosis Research Unit, Department of Clinical Sciences Malmo, Lund University, 205 02, Sweden. ; Department of Medicine and Psychiatry, University of Cantabria, Santander 39011, Spain. ; Department of Internal Medicine, Hospital U.M. Valdecilla- IDIVAL, Santander 39008, Spain. ; Department of Legal Medicine, University of Cantabria, Santander 39011, Spain. ; Centre for Genomic and Experimental Medicine, Institute of Genetics and Molecular Medicine, Western General Hospital, University of Edinburgh, Edinburgh EH4 2XU, UK. ; Department of Reconstructive Sciences, College of Dental Medicine, University of Connecticut Health Center, Farmington, Connecticut 06030, USA. ; Department of Medicine and Physiology, McGill University, Montreal H4A 3J1, Canada. ; Department of Medicine, Oregon Health &Science University, Portland, Oregon 97239, USA. ; Faculty of Medicine in the Galilee, Bar-Ilan University, Safed 13010, Israel. ; Laboratory of Epidemiology, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892, USA. ; Department of Genome Sciences, University of Washington, Seattle, Washington 98195, USA. ; School of Medicine and Pharmacology, University of Western Australia, Crawley 6009, Australia. ; Department of Hygiene and Epidemiology, University of Ioannina School of Medicine, Ioannina 45110, Greece. ; Department of Health Services, Policy and Practice, Brown University School of Public Health, Providence, Rhode Island 02903, USA. ; deCODE Genetics, Reykjavik IS-101, Iceland. ; Framingham Heart Study, Framingham, Massachusetts 01702, USA. ; Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal H3A 1A2, Canada. ; Department of Oncology, Gerald Bronfman Centre, McGill University, Montreal H2W 1S6, Canada. ; Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, The Ohio State University, Columbus, Ohio 43210, USA. ; The Ronald O. Perelman Department of Dermatology and Department of Cell Biology, New York University School of Medicine, New York, New York 10016, USA. ; Department of Diabetes and Endocrinology, Royal Brisbane and Women's Hospital, Brisbane 4029, Australia.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26367794" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bone Density/*genetics ; Bone and Bones/metabolism ; Disease Models, Animal ; Europe/ethnology ; European Continental Ancestry Group/genetics ; Exome/genetics ; Female ; Fractures, Bone/*genetics ; Gene Frequency/genetics ; Genetic Predisposition to Disease/genetics ; Genetic Variation/genetics ; Genome, Human/*genetics ; Genomics ; Genotype ; Homeodomain Proteins/*genetics ; Humans ; Mice ; Sequence Analysis, DNA ; Wnt Proteins/genetics
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1976), S. 975-983 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that charge exchange mass spectra using various reagent ions can be determined on a commercial double focusing mass spectrometer. The experiment relies upon the presence of a collision region held at a potential above ground with the product ions being selected by their unique kinetic energies. Cyclohexene has been studied in detail and the results are in agreement with previous thermochemical and field ionization kinetics data. Agreement with reported charge exchange spectra of n-propanol, taken at lower energies, is good. The present results, including both the variation of spectra with reagent gas and the small range of kinetic energies present in the charge exchange beam, indicate that a resonant or near resonant process is involved. Thus, the internal energy of the nascent ion is defined within quite narrow limits, just as is the case for charge exchange at lower energy.
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  • 3
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 20 (1985), S. 511-514 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ion-molecular reaction behavior of ten morphine alkaloids with several commonly used reagent gases are studied under chemical ionization mass spectrometry conditions. These studies emphasize the correlation of the structural characteristics of the 10 alkaloids with the following four mass spectrometric parameters: (i) mass shifts of the protonated ion as a result of replacing ammonia with deuterated ammonia as the reagent gas, (ii) relative tendencies of the adduct ion and the protonated ion to lose molecules of water, (iii) relative intensity ratio of the adduct ion and the protonated ion and (iv) tendency of a compound to undergo a reduction reaction.
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  • 4
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    Biological Mass Spectrometry 23 (1988), S. 16-25 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carnitine inner salt, (CH3)3N+ CH2CH(OH)CH2COO-, and carnitine hydrochloride, (CH3)3N+CH2CH (OH)CH2COOH Cl-, in the solid state undergo ion-beam-induced intermolecular methyl transfer reactions as shown by (CH3)3N+ CH2CH(OH)CH2COOCH3 ions at m/z 176 in their positive ion spectra. In the case of carnitine HCl, the product ion is three times as abundant as the intact cation. For the inner salt however, the product is less than one-tenth as abundant as [M + H] +. In both cases, the reaction can be precluded by dissolution of the sample, supporting an intermolecular mechanism. The negative ion spectra for these compounds contain no [M - CH3]- ions, suggesting that simple transmethylation does not occur. Rather it is proposed that the inner salt abstracts a methyl group from the intact carnitine cation to yield [M + CH3]+ and a neutral species, the driving force being a minimization of the total number of charges desorbed into the gas phase. Thermodynamic data favor this mechanism as do data for other carnitine salts. The reaction appears to be inhibited when one reactant is present in excess. This is the case for carnitine HNO3 and CH3SO3H, which tend to liberate the intact cation since the anions are large and polarizable. It is also the case for small, hard anions like fluoride, which appear to favor release of the inner salt, hence the cation at m/z 162 is of low abundance and the transmethylation product (m/z 176) is absent. The extent of the reaction is also dependent on the methods of preparation of the sample, and deposition of the salts from solution greatly reduces the extent of methyl transfer. [M - CH3]- is observed when glycerol is used as a matrix, possibly due to a matrix-analyte methyl transfer reaction.
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  • 5
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    Biological Mass Spectrometry 16 (1981), S. 145-146 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 6
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    Biological Mass Spectrometry 25 (1990), S. 409-414 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three of the main oxygen-containing fragments resulting from 3-methyl-2-butyl trifluoroacetate (11) had been identified previously as the 1-triflnoroacetoxyethyl cation (m/z 141, 12, product of simple cleavage), and the products of single (m/z 142) and double hydrogen transfer (m/z 143, protonated ethyl trifluoroacetate). Collisionally activated dissociation of m/z 142 and the isotopomers resulting from 11-2-d, 11-1-d3, 11-5,6-d6, and 11-18O2 has established that m/z 142 is the oxygen protonated 1-trifluoroacetoxyethyl free radical (17) formed by hydrogen shift irom a γ-methyl group to oxygen in the molecular ion, rather than in a complex (18) between 12 and the 2-propyl free radical, as expected based on a mechanistic model existing in the literature. The second hydrogen transferred originates in the other γ-methyl group; its migration may occur, but does not have to, in the complex between 17 and a molecule of propene, prior to dissociation of the two fragments. Collision-activated dissociation has now shown that the m/z 140 ion observed in the spectrum is the molecular ion of vinyl trifluoroacetate, possibly formed by a hydrogen transfer from 12 to the 2-propyl radical in the complex 18. The hydrogen migration to oxygen exhibits no isotope effect, whereas the transfers to carbon atoms exhibit small primary and α secondary kinetic isotope effects. Exclusive migration of the tertiary hydrogen from C(3) occurs in the formation of 2-methylbutene cation radical (m/z 70) from the molecular ion. The hydrocarbon ion fragments and the heteroatom-containing fragments are formed from 11 by disjoint pathways.
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  • 7
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Like most dyes, Basic Yellow 2 (BY-2) fades upon prolonged exposure to light. Light-induced fading is a complex process that is also affected by heat and humidity. In order to better understand the photodegradation process and to identify the various photodegradation products of BY-2, fabric samples and solutions containing BY-2 were exposed to a variety of fading conditions. The analysis of faded BY-2 dyed fabric extracts by high-performance liquid chromatography/mass spectrometry (HPLC/MS) indicated the reduction and hydrolysis of the C=NH2+ group to form primarily benzophenone derivatives, as well as various demethylated products. Due to the absence of fragmentation in the thermospray spectra (only [M + H]+ ions were observed) the dye extracts were analyzed by gas chromatography/mass spectrometry (GC/MS) to confirm the identity of the degradation products. Many of the degradation products were sufficiently volatile for analysis by GC/MS. Mass spectra of the photodegradation products of BY-2 exhibited molecular ions and structurally important fragment ions to complement the thermospray data. The mass spectral data indicated that the most prevalent degradation product formed was ((CH3)2NC6H4)2C=0 (Michler's ketone). Hydrolysis of the C=NH2+ group to C=0 is the main color-destroying reaction in the fading of BY-2. Demethylation products which can alter the shades of color were also detected in the faded BY-2 samples.
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  • 8
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    Biological Mass Spectrometry 19 (1990), S. 597-600 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermospray mass spectrometry of inositol mono- and polyphosphates, separated by ion-exchange chromatography, was evaluated for its potential as a general method for quantitative analysis of these substances. The only ions of significant abundance that are produced by the thermospray ionization process result from the total loss of phosphate from inositol. Thus inositol mono-, tris- and hexakisphosphate each gave mass spectra consisting solely of [MH]+ and [MNH4]+ of inositol. When the chromatographic eluates are passed through a heated reactor prior to the thermospray source maximal yields of these ions are obtained. The sensitivity of the technique falls short of that needed for a general method for biological applications, because the lower limit of detection is about 100 pmol μl-1. Inositol phosphates peracetylated on C-hydroxyls were also studied, with separation by ion-exchange chromatography. Again, thermospray ionization produces totally dephosphorylated species, with the highest-mass ions retaining all of the acetyl groups, even when using the thermal reactor. Losses of acetate were also observed. Sensitivity with the acetyl derivative was comparable to that with the underivatized inositol phosphates.
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    Biological Mass Spectrometry 20 (1991), S. 339-344 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Volatile mass calibration standards have been prepared by esterifying β-cellobiose (4-β-D-glucopyranosyl-D-glucose) with a mixture of heptafluorobutyric (HFB) anhydride and pentafluoropropionic (PFP) anhydride. The mixed esters produce spectra that are useful for mass spectrometer calibration with positive or negative ion methane chemical ionization and electron impact over the mass range 300-2000. The spectra contain prominent ions spaced at m/z 20 and m/z 50 intervals. Using the mixed ester with direct insertion probe introduction gives intense spectra that persist for tens of minutes. All signals above m/z 194 derived from these substances disappear rapidly upon withdrawal of the probe. The composition and exact masses are given for the positive and negative ion spectra of a mixed HFB/PFP ester of β-cellobiose. Two other calibrants are described: one made from β-cellobiose using a mixture of HFB, PFP and trifluoroacetic anhydrides, and another the HFB/PFP mixed ester of perseitol. These are examples of the flexibility of this approach with respect to mass range and ion composition.
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 21 (1992), S. 363-364 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The present report demonstrates that thermospray liquid chromotography/mass spectrometry (LC/MS) calibration can be easily achieved by the observation of water cluster ions in filament-on or discharge ionization modes. Cluster ions of sizes ranging from 1 to 44 water molecules are readily observed and thus are useful over the mass range from 17 to 792 Da.
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