Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    NMR spectroscopic studies on kinetics and thermodynamics of reversible dissociation reactions. 6. Ionization of tropylium azide in liquid sulfur dioxide and selective migration of the azide ligand in less polar solvents (1979)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 101 (1979), S. 1943-1950 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00502a003
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Detection and identification of the cross-linking amino acidsN τ-andN π-(2′-amino-2′-carboxy-ethyl)-l-histidine (“histidinoalanine”, HAL) in heated milk products (1993)
    Springer
    European food research and technology 197 (1993), S. 114-117 
    Details
    ISSN: 1438-2385
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Summary An unknown ninhydrin positive compound, X, was detected in acid hydrolysates of heated skim milk samples by amino acid analysis, eluting between phenylalanine and pyridosine in the chromatogram. The formation of X correlated with heating time and temperature. preparative ion-exchange chromatography enabled the isolation of X and a second minor compound from a milk protein hydrolysate and from a model mixture consisting of Nα-acetylhistidine and methyl-2-acetamidoacrylate (acetyldehydroalaninmethylester), in a relative abundance of 8 to 1. By1H-NMR spectroscopy, the two compounds could be identified as the Nτ- and Nπ-isomers of N-(2′-amino-2′-carboxy-ethyl)-l-histidine (histidinoalanine), a cross-link amino acid that has not been described in food proteins up to now. In a number of foods containing milk protein, the Nτ-histidinoalanine contents were between 50 and 1800 mg/kg protein, which is in a concentration range comparable to the potential nephrotoxic cross-link lysinoalanine, which was determined simultaneously.
    Notes: Zusammenfassung In Säurehydrolysaten erhitzter Magermilch konnte am Aminosäureanalysator im Elutionsbereich zwischen Phenylalanin und Pyridosin eine unbekannte Verbindung, X, nachgewiesen werden, deren Bildung mit der Erhitzungszeit und -temperatur korrelierte. Durch präparative Ionenaustauschchromatographie gelang die Isolierung von X und einer zweiten Minorkomponente aus einem Milchproteinhydrolysat sowie einem Modellansatz bestehend aus Nα-Acetylhistidin undx` 2-Acetamidoacrylsäuremethylester (“Acetyldehydroalaninmethylester”) im Mengenverhältnis von 8 zu 1.1H-NMR-spektroskopische Untersuchungen ermöglichten die eindeutige Identifizierung der beiden Verbindungen als Nτ- und Nπ-Isomer vonN-(2′-Amino-2′-carboxyethyl)-l-histidin (“Histidinoalanin”). Diese Crosslink-Aminosäuren waren bisher noch nicht in Lebensmitteln nachgewiesen worden. Die Gehalte an Nτ-Histidinoalanin in einer Anzahl milchproteinhaltiger Lebensmittel lagen mit 50 bis 1800 mg/kg Protein in einer mit der simultan quantifizierten, potentiell nierentoxischen Crosslink-Aminosäure Lysinoalanin vergleichbaren Größenordnung.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01260304
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Detection and identification of a protein-bound imidazolone resulting from the reaction of arginine residues and methylglyoxal (1994)
    Springer
    European food research and technology 199 (1994), S. 55-58 
    Details
    ISSN: 1438-2385
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Abstract A ninhydrin-positive compound was detected in acid hydrolysates of various alkali-treated bakery products (pretzels, snack bars), eluting immediately after pyridosine in amino acid chromatograms. Following preparative isolation from a food sample and independent synthesis, the compound was unequivocally identified by fast-atom bombardement-mass spectrometry,1H- and13C-nuclear magnetic resonance as a protein-bound imidazolone, existing in two tautomeric forms, namelyN δ-(5-methyl-4-oxo-5-hydroimidazol-2-yl) -L-ornithine andN δ-(4-methyl-5-oxo-4-hydroimidazol-2-yl) -L-ornithine. The acid-labile amino acid derivative is formed by direct condensation of the guanido group of arginine and methylglyoxal, a sugar degradation product, and represents a previously unknown post-translational protein modification. For a number of commercially available alkali-treated bakery products, the amounts of the imidazolone after complete enzymic digestion ranged between 900 and 1300 mg per 100g protein, indicating that between 20 and 30% of the arginyl residues might react with methylglyoxal during the bakery process.
    Notes: Zusammenfassung In Säurehydrolysaten verschiedener Laugenbackwaren (Brezeln, Knabberartikel) wurde eine im Aminosäurechromatogramm unmittelbar nach Pyridosin eluierende ninhydrinpositive Verbindung nachgewiesen. Sie konnte nach präparativer Isolierung aus einer Lebensmittelprobe sowie nach unabhängiger Synthese mittels FAB-MS,1H- und13C-NMR eindeutig als proteingebundenes Imidazolon identifiziert werden, welches in den zwei tautomeren FormenN δ-(5-Methyl-4-oxo-5-hydroimidazol-2-yl)-l-ornithin undN δ-(4-Methyl-5-oxo-4-hydroimidazol-2-yl)-l-ornithin vorliegt. Das säurelabile Aminosäurederivat entsteht durch direkte Kondensation der Guanidinogruppe von Arginin mit dem Zuckerabbauprodukt Methylglyoxal und ist Vertreter einer neuen Form posttranslationaler Proteinmodifikationen. Für eine Anzahl handelsüblicher Laugenbackwaren lagen die nach enzymatischer Totalhydrolyse bestimmbaren Gehalte des Imidazolons zwischen 900 und 1300 mg pro 100g Protein. Während des Backprozesses werden somit zwischen 20 und 30% der Argininreste mit Methylglyoxal umgesetzt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01192954
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Studies on the formation of lysinomethylalanine and histidinomethylalanine in milk products (1994)
    Springer
    European food research and technology 199 (1994), S. 243-247 
    Details
    ISSN: 1438-2385
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Abstract From reaction mixtures consisting ofN-acetyldehydroaminobutyric acid methyl ester andN α-acetyl-l-lysine orN α-acetyl-l-histidine, respectively, distinct amounts of the cross-link amino acidsN ε-(2-amino-2-carboxy-l-methylethyl)-l-lysine (lysinomethylalanine, LMeAL) andN τ-(2′-amino-2′-carboxy-1′-methyl-ethyl)-l-histidine (histidinomethylalanine, HMeAL) were isolated via preparative ion-exchange chromatography and identified by1H- and13C-nuclear magnetic resonance. In the amino acid chromatogram, both compounds eluted clearly separated from other basic amino acids. However, neither LMeAL nor HMeAL could be detected in numerous acid hydrolysates of a range of milk products. In model studies, threonine showed a significantly lower tendency for an alkali-induced β-elimination reaction compared to serine. The reactivity of the resulting dehydroaminobutyric acid towards nucleophiles was more than tenfold lower as compared to dehydroalanine. Thus, the formation of LMeAL as well as of HMeAL during food processing is negligible.
    Notes: Zusammenfassung Aus Reaktionsansätzen bestehend ausN-Acetyldehydroaminobuttersäurenthylester undN α-Acetyl-l-lysin beziehungsweiseN α-Acetyl-l-histidin konnten die Crosslink-AminosäurenN ε-(2-Amino-2-carboxy-1-methyl-ethyl)-l-lysin (Lysinomethylalanin, LMeAL) undN τ-(2′ amino-2-carboxy-2′ -methyl-ethyl)-l-histidin (Histidinomethylalanin, HMeAL) durch präparative Ionenaustauschchromatographie isoliert und anschließend durch 1H-und13C-NMR identifiziert werden. Das Aminosäurechromatogramm zeigte eine eindeutige Trennung beider Aminosäurederivate von anderen basischen Aminosäuren. Dennoch konnten in einer großen Zahl von Säurehydrolysaten der verschiedensten Milchprodukte weder LMeAL noch HMeAL nachgewiesen werden. In Modelluntersuchungen erfolgte die β-Elimination an Threonin im Vergleich zu Serin in einem deutlich geringeren Maße. Die Reaktivität der dabei entstehenden Dehydroaminobuttersäure gegenüber Nucleophilen war mehr als zehnfach geringer als die von Dehydroalanin. Damit kann die Bildung sowohl von LMeAL als auch von HMeAL bei der Verarbeitung von Nahrungsmitteln als vernachlässigbar gering eingeschätzt werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01193454
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    A simple method for the preparation of furosine and pyridosine reference material (1994)
    Springer
    European food research and technology 198 (1994), S. 66-67 
    Details
    ISSN: 1438-2385
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Abstract After heatingN α-acetyllysine and glucose for 4 h at 90 °C in the dry state and subsequent acid hydrolysis with 7.8 N HCl, preparative fractionation of the dihydrochlorides of furosine and pyridosine was achieved by cation-exchange chromatography. The lysine derivatives could be prepared with high yield and sufficient purity for the use as reference material.
    Notes: Zusammenfassung Nach dem Erhitzen vonN α-Acetyllysin und Glucose für 4 h bei 90 °C in trockenem Zustand und nachfolgender Hydrolyse mit 7.8 N HCl erfolgte eine präparative Fraktionierung der Dihydrochloride von Furosin und Pyridosin durch Kationenaustauschchromatographie. Die Lysinderivate wurden in guter Ausbeute und in für Referenzmaterial ausreichender Reinheit erhalten.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01195287
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Molecular characterization of the genomes of actinophages SH3, SH10, SH11, and SH12 infecting Streptomyces hygroscopicus (1979)
    Springer
    Molecular genetics and genomics 172 (1979), S. 319-327 
    Details
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Some physico-chemical properties of the DNAs released from the actinophages SH3, SH10, SH11, and SH12 are described. The four phage DNAs have a linear double-stranded secondary structure and are unique with respect to their high G·C contents which, from melting studies and buoyant density experiments, were found to be in the range of 68–73 mol-%. The DNA molecular weights were determined by sedimentation velocity experiments and by electron microscopic length measurements, the mean values of the two corresponding data sets being 34.0·106 (SH3), 26.7·106 (SH10), 26.1·106 (SH11), and 28.7·106 (SH12) with a mean relative error of ±5%. From different observations it was concluded that SH10 DNA, and possibly also SH11 and SH12 DNA, have cohesive ends and can undergo intramolecular or intermolecular association to form ring-like monomers or linear and ring-like multimers. Cleavage of the DNAs of SH3, SH10, SH11, and SH12 by EcoRI restriction endonuclease delivered two, one, zero, and two cleavage sites, respectively, and by BamHI restriction endonuclease eight, zero, zero, and zero cleavage sites, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00271732
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    NMR-Spektroskopische Untersuchungen zur Kinetik und Thermodynamik reversibler Dissoziationsreaktionen, V. Das Gleichgewicht zwischen Kontaktionenpaaren des Tropyliumisothiocyanats und kovalentem 7-Isothiocyanatocycloheptatrien  -  1H- und 13C-NMR-Messungen (1978)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 111 (1978), S. 2947-2959 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: NMR Spectroscopic Studies on Kinetics and Thermodynamics of Reversible Dissoziation Reactions, V. Equilibrium between Contact Ion Pairs of Tropylium Isothiocyanate and the Covalent 7-Iso-thiocyanatocycloheptatriene - 1H and 13C NMR InvestigationsBoth the ionic and the covalent form of tropylium isothiocyanate have been directly observed in low temperature 1H and 13C NMR spectra. The isothiocyanate structure of the covalent molecule is proved by IR and 13C NMR spectra (for comparison the 13C NMR spectra of several isothiocyanates and thiocyanates as well as cycloheptatriene derivatives have been recorded). NMR and UV spectra give evidence for the ionic form to be contact ion pairs. Complete line shape analysis in CS2/CDCl3 (10:1) give evidence for a random migration mechanism of the isothiocyanate shift around the cycloheptatriene ring. The resulting kinetic parameters are ΔG298≠ = 14.79 ± 0.05 kcal/mol, ΔH≠ = 11.73 ± 0.4 kcal/mol, and ΔS≠ = -10.3 ± 1.3 e. u. Ion pairs are discussed as intermediates for the migration process.
    Notes: Die kovalente und die ionische Form der Titelverbindung lassen sich in den Tieftemperatur-NMR-Spektren direkt nebeneinander nachweisen. Die Struktur des kovalenten Isothiocyanates wird durch seine IR- und 13C-NMR-Spektren belegt (zum Vergleich wurden die 13C-NMR- Spektren einer Reihe von Isothiocyanaten, Thiocyanaten und Cycloheptatrien-Derivaten auf-genommen). Die NMR- und UV-Spektren beweisen, daß die Ionen als Kontaktionenpaare vorliegen. Die Linienformanalyse für die statistische Wanderung des Isothiocyanatrestes um den Cycloheptatrienring führt zu den folgenden Aktivierungsparametern: ΔG298≠ = 14.79 ± 0.05 kcal/mol. ΔH≠ = 11. 73 ± 0.4 kcal/mol und ΔS≠ = -10.3 ± 1.3 e. u. Ionenpaare werden bei der Wanderung als Zwischenstufen angenommen.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19781110824
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Direkte Beobachtung des Dissoziationsgleichgewichtes bei TropyliumsalzenHerrn Professor Karl Winnacker zum 70. Geburtstag gewidmetDiese Arbeit wurde von der Deutschen Forschungsgemeinschaft und dem Fonds der Chemischen Industrie unterstützt. (1973)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 85 (1973), S. 821-822 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19730851810
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Direct Observation of the Dissociation Equilibrium of Tropylium SaltsDedicated to Professor Karl Winnacker on the occasion of this 70th birthdayThis work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. (1973)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 12 (1973), S. 773-774 
    Details
    ISSN: 0570-0833
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197307731
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    facet.materialart.
    Unknown
    UmetaFlow: An untargeted metabolomics workflow for high-throughput data processing and analysis (2023)
    Details
    Publication Date: 2023-10-06
    Description: Metabolomics experiments generate highly complex datasets, which are time and work-intensive, sometimes even error-prone if inspected manually. Therefore, new methods for automated, fast, reproducible, and accurate data processing and dereplication are required. Here, we present UmetaFlow, a computational workflow for untargeted metabolomics that combines algorithms for data pre-processing, spectral matching, molecular formula and structural predictions, and an integration to the GNPS workflows Feature-Based Molecular Networking and Ion Identity Molecular Networking for downstream analysis. UmetaFlow is implemented as a Snakemake workflow, making it easy to use, scalable, and reproducible. For more interactive computing, visualization, as well as development, the workflow is also implemented in Jupyter notebooks using the Python programming language and a set of Python bindings to the OpenMS algorithms (pyOpenMS). Finally, UmetaFlow is also offered as a web-based Graphical User Interface for parameter optimization and processing of smaller-sized datasets. UmetaFlow was validated with in-house LC–MS/MS datasets of actinomycetes producing known secondary metabolites, as well as commercial standards, and it detected all expected features and accurately annotated 76% of the molecular formulas and 65% of the structures. As a more generic validation, the publicly available MTBLS733 and MTBLS736 datasets were used for benchmarking, and UmetaFlow detected more than 90% of all ground truth features and performed exceptionally well in quantification and discriminating marker selection.
    Language: English
    Type: article , doc-type:article
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    OPUS
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...