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  • 2015-2019
  • 1985-1989  (1,737)
  • 1987  (1,737)
  • Analytical Chemistry and Spectroscopy  (1,177)
  • Biochemistry and Biotechnology  (560)
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  • 2015-2019
  • 1985-1989  (1,737)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987) 
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 13-19 
    ISSN: 0887-3585
    Keywords: two-dimensional electrophoresis ; ethylnitrosourea ; somatic mutations ; structural variants ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The feasibility of detecting human somatic structural gene mutations by two dimensional electrophoresis has been investigated. A lymphoblastoid cell line was grown as a mass culture in the presence of ethylnitrosourea, after which cells were regrown as single cell clones. A total of 257 polypeptide spots were analyzed in gels derived from 186 clones. Four structural mutations were detected by visual analysis of the gels. Computer analysis of gels corresponding to the mutant clones was also undertaken. At a spot size threshold of 200 spots to be matched using a computer algorithm, all four mutant polypeptides were detected. These results indicate the usefulness of the two-dimensional approach for mutagenesis studies at the protein level.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 1-12 
    ISSN: 0887-3585
    Keywords: protein crystallography ; protein refinement ; empirical energy simulations ; error analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The uncertainties in the refined parameters for a 1.5-Å X-ray structure of carbon-monoxy (FeII) myoglobin are estimated by combining energy minimization with least-squares refinement against the X-ray data. The energy minimization, done without reference to the X-ray data, provide perturbed structures which are used to restart conventional X-ray refinement. The resulting refined structures have the same, or better, R-factor and stereochemical parameters as the original X-ray structure, but deviate from it by 0.13 Å rms for the backbone atoms and 0.31 Å rms for the sidechain atoms. Atoms interacting with a disordered sidechain, Arg 45 CD3, are observed to have larger positional uncertainties. The uncertainty in the B-factors, within the isotropic harmonic motion approximation, is estimated to be 15%. The resulting X-ray structures are more consistent with the energy parameters used in simulations.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 20-33 
    ISSN: 0887-3585
    Keywords: calmodulin ; peptide ; calmodulin-binding peptide ; peptide design ; hydrophobic moment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A basic, amphiphilic α helix is a structural feature common to a variety of inhibitors of calmodulin and to the calmodulin-binding domains of myosin light chain kinases. To aid in recognizing this structural feature in sequences of peptides and proteins we have developed a computer algorithm which searches for sequences of appropriate length, hydrophobicity, helical hydrophobic moment, and charge to be considered as potential calmodulin-binding sequences. Such sequences occurred infrequently in proteins of known crystal structure. This algorithm was used to find the most likely site in the catalytic (γ) subunit of phosphorylase b kinase for interaction with calmodulin (the δ subunit). A peptide corresponding to this site (residues 341-361 of the γ subunit) was synthesized and found to bind calmodulin with approximately an 11 nM dissociation constant. A variant of this peptide in which an aspartic acid at position 7 in its sequence (347 of the γ subunit) was replaced with an asparagin was found to bind calmodulin with approximately a 3 nM dissociation constant.
    Additional Material: 8 Ill.
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  • 5
    ISSN: 0887-3585
    Keywords: proteolytic cleavage ; immunological cross-reaction ; amber fragment ; temperature-sensitive mutant ; stationary growth-phase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Immunological cross-reaction was employed for identification of proteolytic fragments of E. coli RNA polymerase genered both in vitro and in vivo. Several species of partially denatured but assembled RNA polymerase were isolated, which were composed of fragments of the two large subunits, β and β′, and the two small and intact subunits, α and σ. Comparison of the rate and pathway of proteolytic cleavage in vitro of unassembled subunits, subassemblies, and intact enzymes indicated that the susceptibility of RNA polymerase subunits to proteolytic degradation was dependent on the assembly state.Using this method, degradation in vivo was found for some, but not all, of the amber fragments of β subunit in merodiploid cells carrying both wild-type and mutant rpoB genes. Although the RNA polymerase is a metabolically stable component in exponentially growing cells of E. coli, degradation of the full-sized subunits was found in two cases, i.e., several temperature-sensitive E. coli mutants with a defect in the assembly of RNA polymerase and the stationary-phase cells of a wild-type E. coli. The in vivo degradation of RNA polymerase was indicated to be initiated by alteration of the enzyme structure.
    Additional Material: 9 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 54-63 
    ISSN: 0887-3585
    Keywords: domain association ; protein folding ; viscosity dependence ; solvent effects ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The equilibria and kinetics of ureainduced unfolding and refolding of the α subunit of tryptophan synthase of E. coli have been examined for their dependences on viscosity, pH, and temperature in order to investigate the properties of one of the rate-limiting steps, domain association. A viscosity enhancer, 0.58 M sucrose, was found to slow unfolding and accelerate refolding. This apparently anomolous results was shown to be due to the stabilizting effect of sucrose on the folding reaction. After accounting for this stabilization effect by using linear free-energy plots, the unfolding and refolding kinetics were found to have a viscosity dependence. A decrease in pH was found to stabilize the domain association reaction by increasing the refolding rate and decreasing the unfolding rate. This effect was accounted for by protonation of a single residue with a pK value of 8.8 in the native state and 7.1 in the intermediate, in which the two domains are not yet associated. The activation energy of unfolding is 4.8 kcal/mol, close to the diffusion limit. The negative activation entropy of unfolding, -47 cal/deg-mol, which controls this reaction, may result from ordering of solvent about the newly exposed domain interface of the transition state. These results may provide information on the types of noncovalent interactions involved in domain association and improve the ability to interpret the folding of mutants with single amino-acid substitutions at the interface.
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 34-41 
    ISSN: 0887-3585
    Keywords: adrenergic receptors ; affinity chromatography ; electron microscopy ; oligomeric structure ; target size analysis ; HPLC digest mapping ; receptor evolution ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have characterized the structure of purified beta-adrenergic receptors by a combination of photoaffinity labeling, high performance liquid chromatography (HPLC)-tryptic mapping, CNBr fragmentation, target size analysis, and electron microscopy of purified receptor molecules. Guinea pig lung beta-adrenergic receptors purified by affinity chromatography, ion exchange chromatography, and HPLC size exclusion chromatography or photoaffinity labeled with [125]-iodocyanopindolol diazirine displayed mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) that corresponded to Mr = 68,000. Purified, radioiodinated guinea pig lung beta-receptors were subjected to complete trypsin digestion and subsequent reverse-phase HPLC analysis, which revealed nine peptides. Active site labeling and tryptic digestion of partially purified hamster lung beta-receptors produced one peptide, whereas CNBr digestion of the same material produced two labeled fragments, yielding information about the location of the active site within the primary sequence. Purified guinea pig lung receptors were examined with transmission electron microscopy. Electron micrographs revealed slightly asymmetric, rod-shaped structures with an average length of 13 nm and width of 3.4 nm. Many receptors were arranged as apparent dimeric structures. These findings confirm data obtained from target size analysis of guinea pig lung beta-receptors in situ which suggest that receptors may exist as oligomeric arrays in the native membrane. Taken together, these data provide information about putative functional domains of the beta-adrenergic receptor and its quaternary structure.
    Additional Material: 8 Ill.
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  • 8
    ISSN: 0887-3585
    Keywords: intrahelical ion pairs ; frequency of ion pairs in exposed helices ; alpha-helix stabilization ; protein tertiary structure stabilization ; protein-folding pathway ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A survey of 47 globular proteins was made to determine the probability of occurrence of ion pairs separated by 1, 2, 3, … and 8 residues in the alpha helices. As a control, the probability of occurrence of like charged pairs was also determined. The survey showed that ion pairs of the type i, i±3 and i, i±4 are the most predominant. Such a preference was not observed for like charged pairs. The observed frequency of ion pairs is significantly greater than their expected frequency. The normalized frequencies of occurrence of the ion pairs were also found to increase generally with the helix length. These results indicate that the ion pairs may contribute to the stability of solvent-exposed alpha helices. Since the stabilization of protein secondary structure, these results may throw light on the mechanism of protein folding.
    Additional Material: 5 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987) 
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 79-80 
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 11
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 72-77 
    ISSN: 0887-3585
    Keywords: CO equilibrium constants ; des-(Arg 141α)HbA ; heme proteins ; high-affinity state ; kinetics ; ligand binding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A few years ago we reported that histidine (HC3) 146β plays a major role in the pH-dependent propeties of the R-state of human hemoglobin, accounting for close to 50% of the R-state Bohr effect. We have extended these studies by examining the role of arginine 141α, another group known to affect the overall Bohr effect. We have compared the pH dependencies of the rate constants for the dissociation and combination of the fourth carbon monoxide molecule, I4 and I′4, respectively, for native hemoglobin A (HbA) and a control reconstututed HbA, and des-(Arg 141α) HbA, the hemoglobin molecule resulting from the enzymatic removal of the C-terminal arginine of the α-chain of human Hb. From these kinetic contants the pH dependence of L4, by about 80% between pH 6 and 8, where the aldkaline Bohr effect normally occurs, The sum of the effects of the removal of His 146β and of Arg 141α is grater than 100%. This suggests that at least one of these modifications altrs the contrubutions of other residues of this Bohr effect.
    Additional Material: 4 Ill.
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  • 12
    ISSN: 0887-3585
    Keywords: hybrid immunologlobulin ; compatible plasmids ; transfection ; mouse IgG1 ; mouse IgG2a ; dansyl ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have produced a series of hybrid IgG1-IgG2a mouse immunoglobulins with identical light chains (L) and variable regions to facilitate the identification of structural features associated with functional differnces between immunoglobulin isotypes. Hybrid heavy chain (H) constant region gene segments were generated by genetic recombination in Escherichia coli between plasmids carrying mouse γ1 and γ2a gene segments. Crossovers occured through out these segments although the frequency was highest in regions of high nucleotide sequence homology. Eleven variant immunoglobulins produced by transfected hybridoma cell lines are assembled into H2L2 tetramers and properly glycosylated. In addition, all 11 immunoglbulins have identical antigen combining sites specific for the fluorescent hapten ε-dansyll-L-lysine. Protein A binding was used as probe of the structural integrity of the Fc portion of the variant antibodies. Differeneces in protein A binding between IgG1 and IgG2a appear to be due to amino acid differances at postions 252 (Thr→Met) and 254 (Thr→Ser) of the heavy chain (EU numbering).
    Additional Material: 8 Ill.
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 111-117 
    ISSN: 0887-3585
    Keywords: crystallography ; antigen ; glycoprotein ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Neuraminidases from different subtypes of influenza virus are characterized by the absence of serlogical cross-reactivity and an amino acid sequence homology of approximately 50%. The three-dimensional structure of the neuraminidase antigen of subtype N9 from an avian influenza virus (A/tern/Australia/G70c/75) has been determined by X-ray crystallography and shown to be folded similarly to neuraminidase of subtype N2 isolated from a human influenza virus. This result demontrates that absence of immunological cross-reactivity is no measure of dissimilarity of polypeptide chain folding. Small differences in the way in which the subunits are organized around the molecular fourfold axis are observed. Insertions and deletions with respect to subtype N2 neuraminidase occur in four regions, only one of which is located within the major antigenic determinants around the enzyme active site.
    Additional Material: 4 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 90-110 
    ISSN: 0887-3585
    Keywords: compact units ; coefficient of compactness ; folding intermediates ; protein structural hierarchy ; primitive units ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The coefficient of compactness was recently introduced and used to locate domains in lysozyme and ribonuclease (Zehfus and Rose: Bio-chemistry 25:5759-5765, 1986). Nineteen additional proteins now have been analyzed by using this measure. Complete listings of compact units and plots showing their hierarchic organization are presented for all twenty-one proteins. Large compact units correspond well to protein domains; however, many smaller compact structures of equal or better compactness are also found. Since small compact units could represent subdomains or protein-folding intermediates, their structural composition is further examined.
    Additional Material: 2 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 118-129 
    ISSN: 0887-3585
    Keywords: homologous proteins ; hydropathy index ; chain flexibility ; α/β barrels ; tryptophan ; synthase aplha subunit ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The amino acid sequences of the α subunits of tryptophan synthase form ten different microorganisms were alingned by standard procedures. The α helics, β strands and turns of each sequence were predicted separately by two standard prediction algorithms and averaged at homologous sequence positions. Additional evidence for conserved secondary structure was derived form profiles of average hydropathy and chain flexibility values, leading to a joint prediction. There is good agreement between (1) predicted β strands, maximal hydropathy and minimal flexibility, and (2) predicted loops, great chain flexibility, and protein segments that accept insertions of various lengths in individual sequences. The α subunit is predicted to have eight repeated β-loop-α-loop motifs with an extra N-terminal α helix and an intercalated segment of highly conserved residues. This pattern suggests that the teritiary structure of the α subunit is an eightfold α/β barrel. The distribution of conserved amino acid residues and publilshed data on limited proteolysis, chemical modification, and mutagenesis are consistent with the α/β barrel structure. Both the active site of the α subunit and the combining site for the β2 subunit are at the end of the barrel formed by the carboxyl-termini of the β strands.
    Additional Material: 6 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 153-161 
    ISSN: 0887-3585
    Keywords: accessbility ; hydrophobic effect ; protein conformation ; Boltzmann statistics ; maximum likelihood ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Globular proteins fold into compact particles with interior amino acid residues shielded from the surounding aqueous environment. An early hypothesis holds that entropic hydophobic forces dirve this phenomenon. However, previous analyses based on a binary description of the accesible surfaces of amino acid residues in proteins did not support theis hypothesis. This report shows that a complete description of accessible surface areas is given by parametric distribution fuctions with three modes. The modes are formed by partitioning the available accessible surface area of the amino acids into three segments; the data for each segment are characterized by a mode-specific model. In the “repulsive” mode, probabilities of accessibility decrease exponentially with exposed surface area, as predicted by the hydrophobic hypothesis. A distinct “buried” mode is needed to account for an excess of residues at or near zero accessibility for most amino acids, consistent with the use of binary descriptions of accessibility. A third mode exists which is termed “near neutral” because it is described by a nearly uniform distribution of accessibility for the hydrophiliic amino acids. Empirical energies calculated for the repulsive mode correlate well with measured free energies of transfer of amino acids from water to organic solvents, while those from the buried mode correlate well with measured free energies of hydration of the side chains. Poor cross correlations between these energies give an explanation for the previous conflict in interpreting these data.
    Additional Material: 2 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 162-166 
    ISSN: 0887-3585
    Keywords: protein folding ; secondary structure prediction ; tertiary structure prediction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In recent years, the protein-folding problem has attracted the attention of molecular biologists. Efforts have focused on developing heuristic and energy-based algorithms to predict the three-dimensional structure of a protein from its amino acid sequence. We have applied a series of heuristic algorithms to the sequence of human growth hormone. A family of five structures which are generically right-handed fourfold α-helical bundles are found from an investigaion of ∼108 structures. A plausible receptor binding site is suggested. Independent crystallographic analysis confirms some aspects of these predictions. These methods only deal with the “core” structure, and conformations of many residues are not defined. Further work is required to identify a unique set of coordinates and to clarify the topological alternatives available to α-helical proteins.
    Additional Material: 3 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 130-152 
    ISSN: 0887-3585
    Keywords: amino acid hydophobicity scale ; QSAR ; amino acids ; peptide side chains ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The fragment method of calculation partition coefficients (P) has been extended to include the common amino acids (AAs). The results indicate that polar and charged side chains influence the hydrophobicity of atoms in the side chain in a predictable manner. Feild effects, as evidenced through polar proximity factors and bond factors, need to be considered for accurate estimation of transfer phenomena. The calculated log P and ΔG°′ values of the 20 AAs agree well with the observed values. Pro calculates to be more hydrophilic than the observed log P. Hydrophobicity scales for peptide side chain residues are compared and evaluated in terms of suitability. Calculated π values for nonpolar side chain residures agree well with the observed values; calculated values for uncharged polar side chain residues deviate by about 0.6 log units except for Gln and Cys; and polar side chain residues with charged side chains calculate as too hydorphilic. Reasons for the differences are explored. We also suggest that tightly bound water to polar moieties in amino acids and peptides may be transferred into the octanol phase during partitioning experiments. A quantitative methodology is persented which characterizes the thermodynamic partitioning of groups and individual atoms in amino acids and proteins.
    Additional Material: 7 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987) 
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 177-187 
    ISSN: 0887-3585
    Keywords: evolution ; protein structure ; nucleotide binding domain ; gene sequence ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The intron/exon organization of the human gene for glycogen phosphorylase has been determined. The segments of the polypeptide chain that corresponds to the 19 exons of the gene are examined for relationships between the three-dimensional structure to the protein and gene structure. Only weak correlations are observed between domains of phosphorylase and exons. The nucleotide binding domains that are found in phosphorylase and other glycolytic enzymes are examined for relationships between exons of the genes and structures of the domains. When mapped to the three-dimensional structures, the intron/exon boundaries are shown to be widely distributed in this family of protein domains.
    Additional Material: 5 Ill.
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  • 21
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 188-201 
    ISSN: 0887-3585
    Keywords: NMR ; NOE ; protein conformation ; structure data base ; structure fragments ; modelling ; distance matrices ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A method to build a three-dimensional protein model from nuclear magnetic resonance (NMR) data using fragments from a data base of crystallographically determined protein structures is presented. The interproton distances derived from the nuclear Overhauser effect (NOE) data are compared to the precalculated distances in the known protein structures. An efficient search algorithm is used, which arranges the distancs in matrices akin to a Cα diagonal distance plot, and compares the NOE distance matrices for short sequential zones of the protein to the data base matrices. After cluster analysis of the fragments found in this way, the structure is built by aligning fragments in overlapping zones. The sequentially long-range NOEs cannot be used in the initial fragments search but are vital to discriminate between several possible combinations of different groups of fragments. The method has been tested on one simulated NOE data set derived from a crystal structure and one experimental NMR data set. The method produces models that have good local structure, but may contain larger global errors. These models can be used as the starting point for further refinement, e.g., by restrained molecular dynamics or interactive graphics.
    Additional Material: 12 Ill.
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  • 22
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 236-259 
    ISSN: 0887-3585
    Keywords: atomic probability distributions of proteins ; anisotropy and anharmonicity of motions in proteins ; multiple occupancy of atomic positions in proteins ; molecular dynamics simulation ; lysozyme ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Positional probability density functions (pdf) for the atomic fluctuations are determined from a molecular dynamics simulation for hen egg-white lysozyme. Most atoms are found to have motions that are highly anisotropic but only slightly anharmonic. The largest deviations from harmonic motion are in the direction of the largest rms fluctuations in the local principal axis frame. Backbone atoms tend to be more nearly harmonic than sidechain atoms. The atoms with the largest anharmonicities tend to have pdfs with multiple peaks, each of which is close to harmonic. Several model pdfs are evaluated on the basis of how well they fit probability densities from the dynamics simulations when parameterized in terms of the moments of the distribution. Gram-Charlier and Edgeworth perturbation expansions, which have been successful in describing the motions of small molecules in crystals, are shown to be inadequate for the distributions found in the dynamics of proteins. Multipeaked distribution functions are found to be more appropriate.
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  • 23
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 260-261 
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 1 Ill.
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  • 24
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987) 
    ISSN: 0887-3585
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 25
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 298-307 
    ISSN: 0887-3585
    Keywords: α-bungarotoxin ; neurotropism ; rhabdo-virus ; α-subunit ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Peptides corresponding to portions of loop 2 of snake venom curare-mimetic neurotoxins and to a structually similar region of rabies virus glycoprotein were synthesized. Interaction of these peptides with purified Torpedo electric organ acetylcholine receptor was tested by measuring their ability to block the binding of 125I-labeled α-bungarotoxin to the receptor. In addition, inhibition of α-bungarotoxin binding to a 32-residue synthetic peptide corresponding to positions 173-204 of the α-subunit was determined. Neurotoxin and glycoprotein peptides corresponding to toxin loop 2 inhibited labeled toxin binding to the receptor with IC50 values comparable to those of nicotine and the competitive antagonist d-tubocurarine and to the α-subunit peptides with apparent affinities between those of d-tubocurarine and α-cobratoxin. Substitution of neurotoxin residue Arg37, the proposed counterpart of the quatenary ammonium of acetylcholine, with a negatively charged Glu residue reduced the apparent affinity about 10-fold. Peptides containg the neutotoxin invarint residue Trp29 had 10- to 100-fold higher affinites than peptides lacking this residue. These results demonstrate that relatively short synthetic peptides retain some of binding ability of the native protein from which they are derived, indicating that such peptides are useful in the study of proetin interactions. The ability of the peptides to compete α-bungarotoxin binding to the receptor with apparent affinites comparable to those of other cholinergic ligands indicates that loop 2 of the neurotoxins and the strucually similar segment of the rabies virus glycoprotein act as recognition sites for the acetylcholine receptor. Invarient toxin residues Arg37 and Trp29 and their viral homologs play important, although not essential, roles in binding, possibly by interaction with complementary anionic and hydrophobic subsites on the acetylcholine receptor. The α-subunit peptide most likely contains all of the determinants for binding of the toxin and glycoprotein peptides present on the α-subunit, because these peptides bind to the 32-residue α-subunit peptides with the same or greater affinity as to the intact subunit.
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  • 26
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 2 (1987), S. 308-329 
    ISSN: 0887-3585
    Keywords: conformational dynamics ; normal mode analysis ; Young's modulus ; rigid structural elements ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The normal mode analysis of conformational fluctuation is carried out for a small globular protein, bovine pancreatic trypsin inhabitor. Results are analyzed mainly to reveal the mechanical construction of the protein molecule. We take dihedral angles, including peptide ω angles, as independent variables for the normal mode analysis. There are 306 such angles in this molecule. Motions in modes with frequencies lower than 120 cm-1 are showned to involve atoms in the whole protein molecule, and spatial change of displacement vectors is continues, i.e., those of atoms near in space are similar. To quantitate the observation of the continuity, a correlation function of direction vectors of atomic displacement is calculated. From this function we define a Quantity that is interpreted as the wave length of an equivalent elastic plane wave. From this Quantity we deduce eefective young's modulus for each mode. For the mode with the lowest frequency 4.4 cm-1, it terned out to be 0.8 × 109 dyn cm-2, the value two orders magnitude softer than, for instance, α-helices. Prompted by this observation, the four lowest frequency modes and also the harmonic motions in the thermal equilibrium are analyzed further mainly to detect relatively rigid structural elements in the molecule. From this analysis emerges a mechanical picture of the protein molecule that is made up of relatively rigid elements held together by very soft parts.
    Additional Material: 15 Ill.
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  • 27
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    Proteins: Structure, Function, and Genetics 2 (1987), S. 330-339 
    ISSN: 0887-3585
    Keywords: van der Waals radii ; conformation ; amino acid residue ; dipeptide approximation ; molecular modeling ; systematic conformationl search ; N-alkyl amino acid ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Effective van der Waals radii were celebrated in such a way that molecular models built from standard bond lengths and bond angels reproduced the amino acid conformations observed by crystallography in proteins and peptides. The celebrations were based on the comparision of the Ramachandbran plots prepared from high-resolution X-ray data of protins and peptides with the allowed φ,ψ torsional angel space for the depeptide molecular models. The celebrated radii are useful as criteria with which to filter energetically improbable conformations in molecular modeling studies of proteins and peptides.
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  • 28
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    Biological Mass Spectrometry 14 (1987) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 29
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    Biological Mass Spectrometry 14 (1987), S. i 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 30
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amino acids can be identified unambiguously in form of their dansylated methyl esters by combination of thin-layer chromatography on polyamide and subsequent mass spectrometry without prior substance elution from the chromatographic polyamide carrier. The evaporation intensity of the amino acid derivatives is sufficient to get excellent mass spectra with significant structural information also with very small amounts of starting material (picomole level), which guarantee a high separation power in the TLC step. Besides the methylester derivatives, in part, products additionally methyl substituted at the sulfonamide nitrogen could be separated.
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  • 31
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The simple combination of thin-layer chromatography on polyamide with subsequent mass spectrometry of the separated compounds together with the carrier material has been employed for unambiguous identification of individual dipeptides in a mixture. The dipeptides were analysed in the form of their dansyl methyl ester derivatives. The appearance of molecular ions in the electron impact mass spectra simultaneously with the ions dans-NH=CHR⌝+ indicating the corresponding N-terminal amino acid residue enables a rapid and sensitive structure elucidation of the dipeptides. The chromatography and mass spectrometry can be performed with 0.2-0.3 nmol dipeptide.
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  • 32
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    Biological Mass Spectrometry 14 (1987), S. 357-362 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several classes of environmentally significant compounds were introduced into an ion trap detector (ITD) by capillary column gas chromatography, and the performance of the device as a gas chromatography/mass spectrometry (GC/MS) system was studied. The experiments conducted included studies of the precision of selected ion monitoring (SIM) measurements, the precision of relative ion abundance measurements in full mass range scans, the sensitivity and instrument detection limits in SIM and full mass range data acquisition, and the linear range of concentration calibration. It was observed that resolution may be lost and saturation may occur under certain conditions, and that the data system can report artifact ions under these conditions.
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  • 33
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Brominated dioxins and dibenzofurans (PBDDs and PBDFs) are known contaminants in commercial fire retardant preparations. Further, they are formed in incineration processes involving polybrominated biphenyl and diphenylether fire retardants. This report presents the characterization of polybrominated dioxins and dibenzofurans. In particular, environmental monitoring methodology for PBDDs and PBDFs has been developed, and confirmation criteria for GC/MS analyses are presented.
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  • 34
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    Biological Mass Spectrometry 14 (1987), S. 473-477 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analysis of reports in the world's literature suggests that average sperm densities for groups of unselected males were relatively constant at about 108 million cells per ml prior to 1950. Subsequent to that time mean sperm densities appear to have declined. Regression analysis indicates the existence of significant negative correlations between mean sperm densities and production of synthetic organic chemicals among other parameters. Phthalate esters are one class of large volume organic chemicals that are known to disturb testicular function in laboratory animals. These compounds are also the most abundant man-made chemicals in the environment. Plots of the concentration of dibutylphthalate in the cellular fraction of ejaculates against either the sperm density or the total number of sperm for the same ejaculates gave two clusters of points. These clusters suggest the existence of two or more populations vis à vis phthalate metabolism; both of which show a negative correlation between phthalate concentration and sperm production.
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  • 35
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    Biological Mass Spectrometry 14 (1987), S. 481-485 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report a case of n-nonacosane storage disease, which went undiagnosed until the death of a 55-year-old farmer. Clinical, histological, and biochemical features are discussed. n-Nonacosane storage was identified by gas chromato-graphic-mass spectrometric analysis of different tissue extracts, n-nonacosane concentration reaching 1.2 mg g-1 of lung tissue and 0.32 mg g-1 of liver tissue. It was possible to rule out a work-induced intoxication, and n-nonacosane storage appeared to be accounted for by a lifelong, heavy consumption of unpeeled apples and Brussels sprouts.
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  • 36
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new technique known as thermally-assisted fast atom bombardment (TA-FAB) has been applied to the analysis of a series of cyclic tetrapeptide mycotoxins in order to demonstrate the usefulness of the method for structural elucidation. TA-FAB uses saturated aqueous solutions of highly hydroxylated compounds, such as fructose, as alternatives to the usual viscous liquid matrices employed in conventional FAB. During the TA-FAB analysis, the probe tip is resistively heated causing diffeiences to occur in the desorption profiles for the analyte and the matrix ions enabling an optimization for analyte desorption as a function of temperature. In this study, direct comparisons are made between TA-FAB, conventional FAB, and electron impact ionization for the analysis of the Helminthosporium carbonum mycotoxins at the 1.5 μg level. The results demonstrate the superior capacity of TA-FAB to provide both molecular weight confirmation and significant fragmentation to aid in the structural elucidation of these important biomolecules.
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  • 37
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    Biological Mass Spectrometry 14 (1987), S. 517-521 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three glutathione conjugates of acetaminophen were characterized by fast atom bombardment/mass spectrometry (FAB/MS) and fast atom bombardment/mass spectrometry/mass spectrometry (FAB/MS/MS). The conjugates, 3-(glutathion-S-yl)acetaminophen, 3-(glutathion-S-yl)diacetaminophen and 3-(diglutathion-S-yl)diacetaminophen showed intense [MH]+ ions at m/z 457, 606 and 911, respectively. Only 3-(glutathion-S-yl)acetaminophen showed any fragmentation by FAB/MS. Structurally characteristic fragmentation was observed with all three conjugates when the [MH]+ ions were collisionally activated. The loss of the glycine (GLY) and glutamic acid (GLU) moieties indicated the presence of at least one glutathione (GSH) group. Multiple losses, some of which could only occur via cleavages in both GSH moieties, were observed with the diglutathione conjugate.
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  • 38
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    Biological Mass Spectrometry 14 (1987), S. 549-553 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A GC-MS procedure has been developed for the quantitation in plasma and urine of rimantadine, an antiviral drug effective against type A influenza. The assay utilizes selective ion monitoring, methane negative ion chemical ionization (NCI) and stable isotope dilution. Sensitivity to NCI is effected by derivation of rimantadine with pentafluorobenzoyl chloride. The method has been used to quantitate plasma concentrations of rimantadine over a range from 4.2 ng/ml to 416 ng/ml, and urinary concentrations of rimantadine over a range of 21 ng/ml to 2077 ng/ml.
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  • 39
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    Biological Mass Spectrometry 14 (1987), S. 127-129 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described to assign the positional series of methylene interrupted polyenoic acids, in complex mixtures, isolated from hydrolysed lipid extracts. It entails a simple comparison of the intensities of three ions of m/z 108, 150 and 192.
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  • 40
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The behaviour of 1,1·,1″-phosphinothioylidinetrisaziridine (thiotepa) in water and aqueous salt solution of various acidity was studied by field ionization mass spectrometry (FI-MS), TLC and potentiometric titration. The rate of thiotepa hydrolysis increased with increasing thiotepa, or sodium chloride concentration, and with decreasing pH. As hydrolysis products of thiotepa, mono- and dichloro derivatives formed in neutral, salt-containing and acidic solution, tepa, and products formed by P—N bond cleavage and release of aziridine have been identified.
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  • 41
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methodology for the qualitative and quantitative analysis of the anthelmintic fenbendazole and its metabolites in goat feces using electron impact (EI)/direct exposure probe (DEP)/mass spectrometric (MS) and tandem mass spectrometric (MS/MS) techniques is presented. Analyses were conducted on extracts from spiked feces and feces from animals treated per os with 5 mg fenbendazole/kg, with samples being collected at zero time and at twelve hour intervals for 144 h. The results of the EI/DEP/MS quantitation of these samples are compared to those for the same samples analysed by high pressure liquid chromatography (HPLC). Mass spectral data for fenbendazole and its metabolites are presented and the advantages of the use of EI/DEP/MS and/or DEP/MS/MS over HPLC are discussed. This methodology may be used as a confirmatory method for the HPLC analysis of fenbendazole and its metabolites or may be used as a method in its own right for the rapid qualitative and quantitative analysis of these compounds.
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  • 42
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Known and possible phenolic and primary and secondary amine metabolites of lidocaine were added to urine from drug-naive rats. These metabolites were derivatized in this aqueous medium by acetylation with acetic anhydride or by pentafluorobenzoylation with pentafluorobenzoyl chloride. The derivatives were simultaneously extracted into an organic solvent. The products were separated by gas chromatography (flame ionization detection for acetates and electron-capture detection for pentafluorobenzoates) and identified by combined gas chromatography/mass spectrometry. Mass spectral fragmentation pathways were readily deduced; diagnostic fragment ions were identified and were valuable for characterization purposes. Structural isomers could be distinguished on the basis of their GC retention times.Extractive derivatization using pentafluorobenzoyl chloride is an attractive analytical procedure for the identification of phenolic and dealkylated metabolites of lidocaine.
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  • 43
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 44
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    Biological Mass Spectrometry 14 (1987), S. 213-220 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermospray HPLC/MS analysis of the metabolites of arachidonic acid proved to be sensitive and specific. The compounds included were hydroxy-fatty acids (5-HETE, 12-HETE, and 15-HETE) and prostaglandins PGD2, PGE2, PGF2α, PGA2, PGA1, TXB2, and 6-Keto-PGF1α. Thermospray HPLC/MS analysis allows for simultaneous monitoring of each compound without the need for additional sample preparation or derivatization. The thermospray spectra for the metabolites exhibited [M + NH4]+ ions and fragment ions because of sequential loss of equivalents of H2O. HPLC/MS showed detection limits in the 0.5 to 5 ng range when using multiple ion detection for most of the metabolites. Post-column derivatization of these metabolites using trimethylanilinium hydroxide (TMAH) to form the methyl esters is also presented. This derivatization resulted in a gain in ion current by a factor of 3-6 for most compounds while adding potential specificity to the analysis. The thermospray spectra of the derivatives were nearly identical to the spectra of the free acid except the peaks were incremented by 14 daltons due to the methyl ester formation. The derivatization of the carboxylic acid group proved to be complete under thermospray conditions producing the maximum ion current and causing no compromise in operation of the interface.
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  • 45
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    Biological Mass Spectrometry 14 (1987), S. 649-651 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The identified urinary metabolites of male rats exposed to indan are: 1- and 2-indanone; 1-, 2- and 5-indanol; 2-and 3-hydroxyl-1-indanone; and cis- and trans-indan-1,2-diol. Indan causes kidney damage in male rats in a manner similar to the cyclic hydrocarbons cis- and trans-decalin and JP-10. Lesions produced by indan occur only in male rats and not in female or control rats.
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  • 46
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dinucleoside monophosphates bearing usual protecting groups at the exocyclic amino functions of the heterocyclic bases, the 5′-hydroxy group, the phosphate moiety and the O-6-position of the guanine ring have been analysed by FAB mass specrometry in the negative ion mode. These non-charged key intermediates for oligodeoxynucleotide synthesis exhibit very simple spectra in the mass range of m/z 400-1500 using tetra-ethylene glycol as matrix. Most of the observed ions could easily be assigned. Apart from deprotonated molecular ions sequence specific ions arising from C-O-P bond cleavage and ions derived from loss of protecting groups were observed. The simplicity of spectra interpretation makes FAB mass spectrometry to a rapid and valuable tool for unambiguous identification of dimeric synthons for oligonucleotide synthesis.
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  • 47
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    Biological Mass Spectrometry 14 (1987), S. 141-142 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 48
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    Biological Mass Spectrometry 14 (1987), S. 131-140 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mixtures of both synthetic and naturally occurring (human plasma) cholesteryl esters have been examined by capillary gas chromatography/mass spectrometry (GC/MS). A magnetic sector mass spectrometer was used and a variety of ionization modes were assessed with a view to obtaining structural information on intact cholesteryl esters. By employing ammonia as reagent gas, with negative ion scanning, spectra were produced from which the nature of steryl and fatty acyl moieties could be readily deduced. Analyses were performed at an ion source temperature of 300°C in order to maintain the integrity of the gas chromatographic profile. The technique described is of general use for the GC/MS analysis of steryl esters, particularly in conjunction with magnetic sector instruments.
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  • 49
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermospray spectra on a magnetic sector mass spectrometer, by definition measured at high accelerating voltages, are seen to be highly fragmented. This is rationalised in terms of the necessity to accelerate ions through a region of high pressure in the vicinity of the ion-collecting orifice at the spray volume, where ions may be energized by ion molecule collisions. In this region, a high percentage of the parent ion current is lost through the dispersion of the ion beam and by the collisional activation of molecular ions resulting in extensive fragmentation. The investigation of means by which these effects may be minimized has led to the construction of an improved sector thermospray source. Comparative results for gramicidin S demonstrate that its fragmentation is reduced and that the intensity of the protonated molecular ion is greatly enhanced.
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  • 50
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    Biological Mass Spectrometry 14 (1987), S. 183-185 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acetates of 12 positionally isomeric tetradecenols (Δ2-Δ13) have been prepared and their mass spectra measured without any prior chemical modification. Comparison of spectra of all the isomers has shown the variation in intensities of some predominant fragments with the position of the double bond on the 14 carbons chain. The mass spectra were interpreted in terms of the relative intensity ratio of the fragment ion peaks to locate the double bond positions. A procedure for elucidation of the positional isomerism of tetradecenyl acetates is given.
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  • 51
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    Biological Mass Spectrometry 14 (1987) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 52
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    Biological Mass Spectrometry 14 (1987), S. 207-211 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Eight normal subjects ingested 125 mg of p-tyramine-β,β-2H2 hydrochloride and the 3 h and following 21 h urine collections were analysed by mass spectrometry with selected ion monitoring for the deuterated metabolites: free and conjugated p-tyramine-β,β-2H2, free p-octopamine-β-2H1, free and conjugated p-hydroxyphenylacetic acid-α-2H1 and -α,α-2H2, and free p-hydroxymandelic acid-α-2H1. These metabolites accounted for 72% of the ingested label, of which conjugated p-tyramine and free p-hydroxyphenylacetic acid constituted 90%. Approximately 50% of the total deuterated tyramine and 70% of the total deuterated p-hydroxyphenylacetic acid were excreted in the first three hours, although there was considerable variation between individuals. The presence of a small amount of p-hydroxyphenylacetic acid-α-2H1 suggests that some exchange of deuterium occurred at the intermediate p-hydrophenylacetaldehyde stage.These results, based as they are on metabolites labelled with the stable isotope deuterium, ought to be more reliable than earlier studies in which unlabelled tyramine was ingested with the resultant metabolites, indistinguishable from their endogenous metabolic counterparts, being measured by fluorimetry or gas chromatography.
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  • 53
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    Biological Mass Spectrometry 14 (1987), S. 221-227 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Human exposure to aromatic amines may be monitored by measuring the amount of sulfinamide adduct bound to hemoglobin. In order to develop a sensitive and selective method for measuring aromatic amines present in low concentrations the mass spectra of the pentafluoropropionamide derivatives of a series of aromatic amines were determined under various ionization conditions. With electron ionization the aromatic amine derivatives typically yield intense molecular ions with fragmentation leading to elimination of C2F5 and COC2F5. Higher molecular weight polycyclic aromatic amines, e.g., 6-aminochrysene, give prominent molecular ions as well as intense ions corresponding to M-174 (loss of CNHCOC2F5). With positive chemical ionization using methane as reagent gas the derivatives give protonated molecular ions as the base peaks, as well as the associated ions at M + 29 and M + 41. Negative ion chemical ionization yields, primarily, peaks corresponding to the loss of HF from the molecular anions. Negative ion chemical ionization with selected ion monitoring is generally more suitable than positive chemical ionization or electron ionization for the quantitative analysis of aromatic amines present in biological samples in the mid femtomolar range. Exposure of human subjects to aromatic amines was determined via basic hydrolysis of the isolated sulfinic acid amide hemoglobin adducts. Analysis of the derivatized extracts by gas chromatography/negative ion chemical ionization/mass spectrometry demonstrated the presence of aniline, ortho-, meta-, and para-toluidine, 2-naphthylamine, and 4-aminobiphenyl. The hemoglobin adduct levels of these amines in both cigarette smokers and nonsmokers were determined. The mean values of the adduct levels of ortho- and para-toluidine, 2-naphthylamine, and 4-aminobiphenyl were higher in smokers than in nonsmokers, while the mean adduct values of aniline and meta-toluidine were similar in both groups. Adducts of 2-, 3-, 4-ethylaniline, 2,3-, 2,4-, 2,5-, 2,6-dimethylaniline, and 3-aminobiphenyl have been detected in smokers' blood. 1-Aminoanthracene, 9-aminophenanthrene, and 6-aminochrysene have not been detected. GC/MS procedures were also used to determine the extent of binding of aniline-2,3,4,5,6-d5 to hemoglobin in rats administered aniline-d5.
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  • 54
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    Biological Mass Spectrometry 14 (1987), S. 479-479 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 55
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The single dose pharmacokinetics of deuterium-labelled cannabinol (2H2-CBN) were evaluated in six male cannabis users with different degree of abuse after smoking an average dose of 19 mg and after intravenous administration of 20 mg CBN. Plasma levels were measured for up to 72 h with selected ion monitoring by GC/MS using 2H7-CBN as internal standard. The systemic availability of smoked CBN was found to be 39 ± 26% (min-max 6-65%). The mean plasma clearance was 19.1 ± 2.6 ml min-1 kg-1 and the volume of distribution was determined to 50 ± 23 1 kg-1. The apparent terminal half lives for CBN were 32 ± 17 h and 43 ± 29 h after intravenous administration and smoking, respectively.
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    Biological Mass Spectrometry 14 (1987), S. 533-534 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Biological Mass Spectrometry 14 (1987), S. 523-531 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Derivatization of prostaglandins and thromboxane B2 using diethyl amino ethyl chloride and diethyl amino ethyl bromide improved thermospray HPLC/MS sensitivity. The derivatization was evaluated for prostaglandin A1, A2, D2, E2, F1α, F2α, and thromboxane B2. The derivatization reaction, thermospray operating conditions, and mode of detection were optimized to produce the most intense [M + H]+ or [M - H]- ions for the derivative. Derivatization was better than 99% complete in 1 hour at 75°C. No thermal degradation of the prostaglandins was observed. Positive thermospray ionization proved the mode most sensitive, enabling detection from 10 to 300 pg of each prostaglandin under multiple ion detection. The thermospray spectra exhibited intense [M + H]+ ions for the derivative with a few fragment ions from sequential losses of water from the [M + H]+ ion. Detection of a prostaglandin metabolite in plasma over the concentration range from 3 ppm to 30 ppb was possible using this derivatization.
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  • 58
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas chromatographic and mass spectrometric properties of leukotriene B4, 20-hydroxy-leukotriene B4 and 20-carboxy-leukotriene-B4 were investigated as their methyl ester trimethylsilyl, methyl ester allyldimethylsilyl and methyl ester tert-butyldimethylsilyl ethers. The gas chromatographic properties of the trimethylsilyl and tert-butyldimethylsilyl ether derivatives were good with respect to peak shape and sensitivity, whereas the allyldimethylsilyl ether derivative gave a lower sensitivity. The sensitivity defined as the quantity that could be passed through the gas chromatographic column.The three derivatives showed a mass spectrometric fragmentation pattern with cleavage of the C12—C13 bond as an important feature. Particularly, the allyldimethylsilyl ether derivative of the three compounds studied exhibited a high tendency for C12—C13 bond cleavage resulting in a fairly intense ion at m/z 435. However, the mass spectra indicated multiple fragmentation pathways due to the presence of double bonds, leading to decreased intensities of the high mass ions. A quantitative analysis by selected ion monitoring of the most intense high mass ions in the respective mass spectrum demonstrated that neither derivative would allow measurements in the low picogram range. Catalytic hydrogenation of the double bonds was performed and the methyl ester trimethylsiyl, methyl ester allyldimethylsilyl and methyl ester tert-butyldimethylsilyl ether derivatives of the reduced compounds were prepared. Saturation of the double bonds increased the gas chromatographic sensitivity for the three derivatives as well as the intensities of the high mass ions in their mass spectra. The high sensitivity that can be obtained by measurement of such high mass ions was demonstrated by quantification of leukotriene B4 in lung tissue samples by selected ion monitoring.
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  • 59
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    Biological Mass Spectrometry 14 (1987), S. 355-355 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 60
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    Biological Mass Spectrometry 14 (1987), S. 363-367 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The indoor air quality of the offices of smokers and nonsmokers was surveyed for volatile organic compound identities and concentrations. These results were examined to determine whether environmental tobacco smoke contamination could be distinguished from airborne pollutants outgassing from other sources. It was not possible to positively attribute volatile organic contaminants to environmental tobacco smoke. It was possible to distinguish between smokers' and nonsmokers' offices by determining airborne nicotine levels.
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  • 61
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxygen-enhanced negative chemical ionization MS is sensitive and specific for the detection of polychlorinated biphenyls (PCBs) without isobaric interferences (qualitative or quantitative) from congeners of higher levels of chlorination. The collision-induced dissociation (CID) spectra of the [M - Cl + O]- ion of 40 PCB congeners have been acquired on a triple quadrupole mass spectrometer.Qualitative relationships between structure of the congener and its CID spectrum suggest that reliable identification of PCB congeners is possible even where capillary column gas chromatographic separation is incomplete. Congeners with hydrogen atoms located para and meta to the biphenyl linkage show most abundant collision-induced loss of HCl, whereas congeners with a penta-chloro phenyl ring show least CID loss of HCl. Congeners IUPAC 105 and 121 have CID spectra suggesting a pathway for sequential loss of HCl and CO neutrals during the collision-induced dissociation of the [M - Cl + O]- ion of these molecules. Unambiguous identification of PCB congeners in natural materials will require a complete set of pure, synthetic PCB congeners: identification problems are illustrated using an extract of Northern Shark (dogfish) liver oil.
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  • 62
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    Biological Mass Spectrometry 14 (1987), S. 535-541 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A moving belt interface was used to identify budesonide metabolites, obtained from rat and mouse liver incubations, by liquid chromatography/mass spectrometry (LC/MS). The metabolites were separated on a small-bore C18 column with an ethanol/water gradient as mobile phase at a flow rate of 0.2 ml min-1. A spray device was used for deposition of the aqueous solvent on to the belt. Chemical ionization mass spectra were obtained with methane as the reagent gas. Deuterium-labelled budesonide, which was used to facilitate metabolite identification by the isotope cluster technqiue, was found to be slightly separated from the unlabelled analogue on the LC column. Incubations were also performed under 18O2 to elucidate the mechanism of a new metabolic pathway (16α, 17α-acetal splitting) and to confirm the oxidative nature of reactions leading to hydroxylated metabolites. The moving belt LC/MS technique afforded higher sensitivity, and gave more abundant MH+ ions of the compounds studied, than previously found by direct probe mass spectrometry. Phthalate ester background, partly from the polymide belt, complicated the identification of minor metabolites.
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  • 63
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    Biological Mass Spectrometry 14 (1987), S. 587-588 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 64
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    Biological Mass Spectrometry 14 (1987), S. 599-602 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the quantification in plasma of CP-55,940, a new non-opiate oral analgetic agent, using capillary gas chromatography/mass spectrometry. After extraction, derivation of the drug and a structural analog internal standard is carried out with trifluoracetyl imidazole. The derivative exhibited excellent gas chrornatographic properties. Electron impact yielded an abundant high mass ion whose monitoring permitted the sensitive and specific determination of CP-55,940 down to 0.5 ng ml-1.
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  • 65
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    Biological Mass Spectrometry 14 (1987), S. 613-616 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the quantification of tulobuterol in human plasma, based upon selective extraction and high resolution capillary gas chromatography-mass spectrometry. The mass spectrometric determination is based on selected ion monitoring of two fragment ions derived from the N,O-heptafluorobutyryl derivatives of tulobuterol and its internal standard, deschlorotulobuterol. The plasma work-up procedure consists of extraction of 1.0 ml alkalinised plasma with dichloromethane, back-extraction into an acidified aqueous phase, followed by a final extraction with dichloromethane after realkalinisation. The method gave interference-free and linear results. The between-assay variability is 4.7% CV at the 3.0 μg l-1 plasma concentration level. The assay permitted quantitative measurements down to 170 ng tulobuterol per litre of plasma and hence provided sufficient sensitivity for quantification of plasma levels after therapeutic doses.
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  • 66
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    Biological Mass Spectrometry 14 (1987), S. 627-632 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In phytochemical and chemotaxonomic research work mass spectrometry plays an outstandingly important role. Using gas chromatography/mass spectrometry (GC/MS) we established the chemotaxa of Tanacetum vulgare L. Chemotypes with essential oils countaining 60-90% of artemisia ketone, carveol, dihydrocarvone, myrtenol, umbellulone, terpinen-4-ol, davanone, and Tagetes species containing various essential oils can be clearly distinguished by their spectra; we examined many variations of Tagetes erecta, T. lucida, T. minuta, T. patula and T. tenuifolia. We have identified α-β-pinene-, 1,8-cineol-, linalool-, camphor-, nerol-, geraniol- and γ-gurjonene as components of Achillea distans L. Injecting the essential oil direct from the oil-secreting organs of T. minuta plants we identified using GC/MS 6-10 and 16% eugenol from the involucral bract and hypsophyll, respectively, as well as β-ocimene, dihydrotagetone, tagetone, Z- and E-ocimenones. In the course of studies on essential fatty acids Borago officinalis and Lappula squarrosa were selected from 70 species of the family Boraginaceae to obtain seed oil as a source of γ-linolenic acid, and for the PG synthesis we isolated several grams of γ-linolenic acid, as well as C18:4, i e. octadecatetraenic acid, from L. squarrosa on the basis of the mass spectra. From the seed oil of Aquilegia vulgaris C18:3 (5) from the oil of Limnanthes dougloasii C20:1 (5) and from the seed oils of Delphinium consolida and of Tropaeolum species (T. majus, T. minus, T. peregrinum) C20:1 (11) fatty acids were identified on the basis of spectra.
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  • 67
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bile from rats treated with acetaminophen was analyzed by direct injection onto a thermospray liquid chromatography/mass spectrometry (LC/MS) system. Two conjugated metabolites of acetaminophen were separated by the high-pressure liquid chromatographic system and analyzed by mass spectrometry. The conjugates were identified as the glutathione-acetaminophen conjugate and the glucuronide-acetaminophen conjugate by comparison of the chromatographic retention times and the mass spectra to that of the synthetic standards. No evidence of acetaminophen metabolites was observed when bile samples were subjected to direct analysis by fast atom bombardment mass spectrometry.
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  • 68
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    Biological Mass Spectrometry 14 (1987), S. 733-736 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
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  • 69
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Direct analysis of unpurified urine from patients with β-ketothiolase deficiency and glutaryl-coenzyme A dehydrogenase deficiency was carried out by methylation and fast atom bombardment mass spectrometry. Previously unidentified signals consistent with unusual acylcarnitines were detected. In the former disease, thermospray liquid chromatography/mass spectrometry analysis confirmed the identification of tiglylcarnitine and differentiated it from a biological isomer, 3-methylcrotonylcarnitine. In glutaric aciduria, glutarylcarnitine was confirmed by detection of glutaric acid liberated upon base hydrolysis of a purified acylcarnitine fraction. The discovery of these metabolites suggests that L-carnitine therapy might be beneficial for the enhanced excretion of toxic metabolites that accumulate in patients with these disorders.
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  • 70
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    Journal of Chemometrics 1 (1987) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 71
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    Journal of Chemometrics 1 (1987), S. 1-2 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 72
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    Journal of Chemometrics 1 (1987), S. 3-6 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 73
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    Journal of Chemometrics 1 (1987), S. 7-18 
    ISSN: 0886-9383
    Keywords: Kalman filter ; Calibration ; Curve resolution ; Parameter estimation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of the Kalman filter to the solution of a variety of problems in analytical chemistry is reviewed. Five examples are selected from the literature to illustrate the use of Kalman filtering techniques for obtaining least-squares estimates fo several parameters of analytical importance. These examples include multicomponent curve resolution and concentration estimation, correction for variable background responses, calibration with drift compensation, and estimation of kinetic parameters for first-order reactions and for heterogeneous charge-transfer reactions. An adaptive Kalman filtering technique is required for the solution of the background correction problem, and the extended Kalman filter algorithm is required for the solution of the nonlinear kinetic problems. For each case, the results that were obtained are summarized, and some advantages of Kalman filtering over traditional least-squares approaches are discussed.
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  • 74
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    Journal of Chemometrics 1 (1987), S. 19-31 
    ISSN: 0886-9383
    Keywords: Calibration ; Indirect calibration ; Multivariate ; Matrix decomposition ; PLS ; PCR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Partial least squares (PLS) modeling is an algorithm for relating one or more dependent variables to two or more independent variables. As a regression procedure it apparently evolved from the method of principal components regression (PCR) using the NIPALS algorithm, which is similar to the power method for determining the eigenvectors and eigenvalues of a matrix. This paper presents a theoretical explanation of the PLS algorithm using singular value decomposition and the power method. The relation of PLS to PCR is demonstrated, and PLS is shown to be one of a continuum of possible solutions of a similar type. These other solutions may give better prediction than either PLS or PCR under appropriate conditions.
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  • 75
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    Keywords: Principal component analysis ; Singular value decomposition ; Factor analysis ; Rank determination ; Eigenvector analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The distribution of error eigenvalues resulting from principal component analysis is deduced by considering the decomposition of an error matrix in which the errors are uniformly distributed. The derived probability function is \documentclass{article}\pagestyle{empty}\begin{document}$$ P(\lambda ^0 _j) = N(r - j + 1)(c - j + 1) $$\end{document} Where λ0j is the jth error eigenvalue, r and c are the numbers of rows and columns in the data matrix, and N is the normalization constant. This expression is tested and validated by investigations involving model data. The distribution function is used to determine the number of factors responsible for various sets of spectroscopic data taken from the chemical literature (including nuclear magnetic resonance, infrared and mass spectra).
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  • 76
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    Keywords: Curve resolution ; Liquid chromatography ; Accuracy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The performance of curve resolution and iterative target transformation curve resolution in quantitative liquid chromatography with a diode array detector is evaluated. Quantitative accuracy of the elution profiles obtained for two- and three-component mixtures has been evaluated as a function of spectral similarity, chromatographic resolution and ratio of the peak areas, using a number of simulations analysed by an analysis of variance. The results obtained by simulation are compared and validated with the results obtained for the separation of phenylene diamines in reversed phase liquid chromatography and proteins in gel permeation liquid chromatography. The results that were obtained are summarized and the chromatographic implications are discussed.
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  • 77
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    Keywords: Multi-way array ; Multiorder array ; Principal components ; PLS ; Multivariate calibration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Lohmöller-Wold decomposition of multi-way (three-way, four-way, etc.) data arrays is combined with the non-linear partial least squares (NIPALS) algorithms to provide multi-way solutions of principal components analysis (PCA) and partial least squares modelling in latent variables (PLS).The decomposition of a multi-way array is developed as the product of a score vector and a loading array, where the score vectors have the same properties as those of ordinary two-way PCA and PLS. In image analysis, the array would instead be decomposed as the product of a loading vector and an image score matrix.The resulting methods are equivalent to the method of unfolding a multi-way array to a two-way matrix followed by ordinary PCA or PLS analysis. This automatically proves the eigenvector and least squares properties of the multi-way PCA and PLS methods.The methodology is presented; the algorithms are outlined and illustrated with a small chemical example.
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  • 78
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    Journal of Chemometrics 1 (1987), S. 73-73 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 79
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    Journal of Chemometrics 1 (1987), S. 75-75 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 80
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    Journal of Chemometrics 1 (1987), S. 74-74 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 81
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    Journal of Chemometrics 1 (1987) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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  • 82
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    Journal of Chemometrics 1 (1987), S. 77-77 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 83
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    Journal of Chemometrics 1 (1987), S. 79-90 
    ISSN: 0886-9383
    Keywords: Numerical deconvolution ; Peak resolution ; Peak separation ; Iterative deconvolution ; Jansson's method ; Super-resolution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Severely overlapped gas chromatographic peaks can be resolved using Jansson's method. Jansson's method is an iterative nonlinear deconvolution technique and consists of Van Cittert's algorithm with the relaxation factor a function of the kth estimate of the peak shape. The maximum peak amplitude of the instrument and peak non-negativity serve as constraints to improve the peak estimate. Super-resolution is achieved without significantly degrading the chromatogram signal-to-noise ratio. The method only requires a knowledge of the instrument impulse response function and maximum peak height.
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  • 84
    ISSN: 0886-9383
    Keywords: NIR ; Fast Fourier transform ; Principal component analysis ; Discrimination ; Baking quality ; Wheat ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Digitalized continuous near infra-red reflectance (NIR) spectra are composed of a great number of data which must be reduced for microcomputer mathematical treatment. The sequence ‘fast Fourier transform preceding principal component analysis’ was tested to perform data size reduction without a large loss of information. The method was applied on a collection of wheat spectra composed of 351 data. Ten resulting data, which described 99.5% of the total variance, were kept. The relevance of the method was estimated by the ability of the resulting data (i) to regenerate the original signal, and (ii) to discriminate the baking quality of the wheat by stepwise multiple discriminant analysis. The average difference between initial and regenerated spectra was -2.4 × 10-3 log (1/R) units and the standard deviation was 1.16 × 10-3 log (1/R) units. The discrimination treatments gave 89.9% of well classified samples for the calibration test and 90.5% for the prediction test. The application of these mathematical treatments to other continuous signals is discussed.
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  • 85
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    Journal of Chemometrics 1 (1987), S. 91-101 
    ISSN: 0886-9383
    Keywords: Factor analysis ; Retention indices ; Model ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Retention indices for 18 monomeric stationary-phase solvents and 33 organic solutes are factor analyzed. Six factors reproduce the data matrix near experimental error. The solvents diglycerol and zonyl E-7 are shown to be highly unique, whereas none of the solutes behaves uniquely. Combination sets of solvent vectors and of solute vectors from the data matrix lead to models having errors within experimental error. Basic factors which might influence the solute - solvent interactions are identified by the least-squares method of target testing. For the solvents, a number of properties, including McReynolds' constants and molecular weight, test successfully. For the solutes, carbon number and group dipole moment are representative properties which test successfully. The best combination of solvent basic factors gives errors about twice the experimental error. Combination sets composed only of McReynolds' constants do not model the data well.
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  • 86
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    Journal of Chemometrics 1 (1987), S. 111-120 
    ISSN: 0886-9383
    Keywords: Principal component analysis ; Submatrix analysis ; Spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the treatment of spectroscopic data by principal component analysis, correct determination of the dimensionality of the data is essential. Submatrix analysis, which involves preliminary analysis of subsets of the data matrix, is described, and shown to be valuable in determining both the size of the factor space and estimates of equilibrium constants in the system, even for data containing abnormally large experimental error.
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  • 87
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    Journal of Chemometrics 1 (1987), S. 135-135 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 88
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    Journal of Chemometrics 1 (1987), S. 136-136 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 89
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    Journal of Chemometrics 1 (1987), S. 121-134 
    ISSN: 0886-9383
    Keywords: Multivariate calibration ; NIR ; Cluster analysis ; Experimental design ; Sample selection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure for selecting samples to use in multivariate calibration, inspired by a paper by Zemroch, is proposed. The method developed is designed for multicollinear data and is based on cluster analysis. It selects among availabe spectra the samples to submit to chemical analysis and calibration. The method is tested on an example from NIR spectroscopy of biscuit dough pieces.
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  • 90
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    Journal of Chemometrics 1 (1987), S. 136-136 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 91
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    Journal of Chemometrics 1 (1987) 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 92
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 137-137 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 93
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 157-173 
    ISSN: 0886-9383
    Keywords: Gas chromatography ; Simplex ; Barycentric co-ordinates ; Discriminant analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper proposes an elegant, yet straightforward, model for classifying linear mixtures. A linear mixture is defined as a random vector y in which the variable are a (non-negative) weighted average of corresponding variables, assumed to characterize g component groups. These weights are referred to as ‘mixing proportions’. The model seeks to identify the mixture constituents and estimate the mixing proportions. It is demonstrated within the context of high resolution gas chromatography and the problem of identifying the constituents in polychlorinated biphenyl mixtures.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 94
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 175-183 
    ISSN: 0886-9383
    Keywords: Deconvolution ; Jansson's method ; Peak resolution ; Numerical deconvolution ; Super resolution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a previous paper,1 Jansson's method was used to deconvolve overlapped gas chromatographic peaks. It was found that this method gave improved performance over conventional techniques such as perpendicular drop and shoulder quantitation.2,3 This paper will present the results of a comprehensive test of Jansson's method using several sample mixtures. These results will be compared to what can be obtained by using shoulder quantitation, perpendicular drop or an instrument with a longer column. A relatively large number of tests will be performed for each of the four mentioned methods of peak resolution, so there will be a reasonable statistical basis for the goodness of Jansson's method to resolve fused gas chromatographic peaks for a given set of instrument conditions. A brief review of Jansson's method and the modeling of a gas chromatographic process will also be presented.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 95
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 139-155 
    ISSN: 0886-9383
    Keywords: Chemical information systems ; Machine-readable structure representation ; Registration search ; Structure search ; Substructure search ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper decribes the development and current state-of-the-art in computerized systems for the storage and retrieval of chemical structure information. The main types of machine-readable structure representation  -  fragmentation codes, linear notations and connection tables  -  are described, together with the retrieval algorithms which are used to provide structure and substructure search facilities. Current research work in chemical structure retrieval includes the development of techniques for the representation and searching of the generic structures which occur in chemical patents, for searching files of three-dimensional structures, for ranking searches designed to identify compounds structurally similar to a given query compound, and the use of parallel computers to increase the efficiency of substructure searching. Chemical structure handling techniques are also applicable in a range of application areas, including chemical reaction indexing, computer-aided synthesis design and structure elucidation, and substructural analysis methods for the study of quantitative structure - activity relationships.
    Type of Medium: Electronic Resource
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  • 96
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 197-197 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 97
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 185-196 
    ISSN: 0886-9383
    Keywords: Cross-validation ; Partial least squares ; Two-sample location ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for statistical analysis of two independent samples with respect to difference in location is investigated. The method uses the partial least squares projections to latent structures (PLS) with cross-validation. The relation to classical methods is discussed and a Monte Carlo study is performed to describe how the distribution of the test-statistic employed depends on the number of objects, the number of variables, the percentage variance explained by the first PLS-component and the percentage missing values. Polynomial approximations for the dependency of the 50 per cent and the 5 per cent levels of the test-statistic on these factors are given. The polynomial for the 50 per cent level is complicated, involving several first-, second- and third-degree terms, whereas the polynomial for the 5 per cent level is dependent only on the number of objects and the size of the first component. A separate Monte Carlo experiment indicates that a moderate difference in sample size does not affect the distribution of the test-statistic. The multi-sample location problem is also studied and the effect of increasing the number of samples on the test-statistic is shown in simulations.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 98
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 198-198 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 197-198 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 1 (1987), S. 198-198 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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