ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

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
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 20 (1985), S. 10-13 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Positive ion electron impact mass spectral data for the four isomeric 17ξ-hydroxy-17ξ-methyl-5ξ-androstane C(3) ketones and the eight isomeric C(3ξ) alcohols are reported. In contrast to earlier reports, no general correlation was observed between the [M—H2O]+·/[M]+· ratio and the configuration at C(17). The ratios of the intensity of several fragment ions to that of the molecular ion do differentiate between the 5α- and 5β-isomers in both C(3) ketones and alcohols, the extent of fragmentation being greater for 5β-steroids. All of these fragments probably involve elimination of a water molecule at some stage in their formation. Elimination of water is also enhanced for 3α- v. 3β-hydroxysteroids, particularly in a 5β-isomer.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four tetrachlorinated bipbenyls were chlorinated with 35Cl2 to yield seventeen polychlorinated biphenyls (PCBs) substituted once or twice with chlorine enriched in 35Cl. Gas chromatographic analysis of the mixtures allowed the identification of the labelled PCBs produced by comparison of their relative retention times with published values. This also permitted the assignment of the position of the labels in these molecules. Mass spectrometric determination of the 35Cl/35Cl ratio of the ions corresponding to successive dechlorination of these PCBs in positive-ion electron impact (EI) allowed quantification of the residual 35Cl label in these ions. Chlorines in the ortho position are lost preferentially to those in meta or para positions. The first dechlorination reaction was found to be totally regioselective for at least two PCB congeners.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron-capture negative-ion chemical Ionization mass spectra of 36 35Cl mono- and di-labelled penta- and hexachlorobiphenyls were studied. Under the conditions of the analyses, the dechlorination of these congeners probably proceeds through electrophilic hydrogen atom attachment followed by rapid loss of the chlorine atom at the same position. These dechlorination reactions occur regioselectively. When present, ortho-chlorines are lost preferentially to meta- and para-chlorines. The extent of the dechlorination reaction, as seen by the relative abundance of the [MH — Cl]- ions, decreases with increasing number of ortho-chlorines.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 12 (1979), S. 352-356 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fluorine magnetic resonance spectroscopy has been used to examine the complexes formed between o- and m-fluorocinnamate ions and the enzyme α-chymotrypsin. Study of the frequency dependence of fluorine spin-lattice and spin-spin relaxation rates suggests that, like the p-isomer, both the o- and m-fluorocinnamates bind equally well to monomeric, dimeric and trimeric forms of the protein. Dipole-dipole interactions with protons of the enzyme play an important role in relaxing the protein-bound fluorine nucleus. Various deuterated forms of the ortho isomer were used to obtain evidence suggesting that the conformation of this molecule bound to the enzyme is similar if not identical to the conformation found in free solution. NMR methods were used to estimate the rates of dissociation of the complexes and the chemical shifts of the bound fluorine atoms were determined to be substantially downfield of their positions in the absence of enzyme.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A comparative mass spectral examination of the trimethylsilyl (TMS) derivatives of 2′-, 3′- and 5′-deoxyadenosine, 2′-, 3′- and 5′-deoxyguanosine, 2′-, 3′- and 5′-deoxyxanothosine and 2′- and 5′-deoxy-2-fluoroadenosine is presented. A general compilation of the major fragment ions found in the low-resolution electron ionization (EI) spectra of the eleven deoxynucleosides is given. Chemical ionization (CI)-collisional activation (CA) daughter ion spectra are reported using the deoxyadenosines as model compounds. Ion structures and fragmentation pathways are proposed for those ions characteristic of each of the isomers. Significant differences in fragmentation exist between the isomeric 2′-, 3′- and 5′-purine deoxynucleosides. The formation and structures of ten ions important in this differentiation are discussed. The CI-CA linked scan spectra provide complementary structural information relative to the EI mass spectra.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A sensitive and specific assay for the quantitative determination of amphetamine, methamphetamine and desmethyldeprenyl in human plasma specimens is described. Electron capture/negative ion chemical ionization gas chromatography/mass spectrometry is used to determine the extracted plasma concentrations of the three target compounds as their N-heptafluorobutyryl derivatives. Quantitation is performed by stable isotope dilution using d6-amphetamine and d6-methamphetamine as internal standards. Selected ion monitoring of the [M - HF]- ions of both the analytes and internal standards results in minimum quantifiable limits of 0.10 ng ml-1 for both amphetamine and methamphetamine and 0.25 ng ml-1 for desmethyldeprenyl. Excellent linearity (r = 0.998) up to at least 5.00 ng ml-1 is demonstrated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...