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  • 1995-1999  (4)
  • Chemistry  (3)
  • Enzymatic sequencing  (1)
  • Key words:Δ5-3β-Hydroxysteroid dehydrogenase  (1)
  • 1
    ISSN: 1432-2048
    Keywords: Key words:Δ5-3β-Hydroxysteroid dehydrogenase ; Δ5-Δ4-Ketosteroid isomerase ; Pregnenolone ; Proges-terone ; Short-chain dehydrogenase/reductases ; Digitalis (cardenolide biosynthesis)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Δ5-3β-Ηydroxysteroid dehydrogenase (Δ5-3β-HSD; EC 1.1.1.145), an enzyme converting pregn-5-ene-3β-ol-20-one (pregnenolone) to pregn-5-ene-3,20-dione (isoprogesterone), was isolated from the soluble fraction of suspension-cultured cells of Digitalis lanata L. strain VIII. Starting with acetone dry powder the enzyme was purified in three steps using column chromatography on Fractogel-TSK DEAE, hydroxyapatite and Sephacryl G-200. Fractions with highest Δ5-3β-HSD activity were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. After in-situ digestion the resulting bands were sequenced N-terminally. The 29-kDa band yielded three fragments with high sequence homology to members of the superfamily of short-chain dehydrogenases/reductases. High similarity was found to microbial hydroxysteroid dehydrogenases. The band may therefore represent the Δ5-3β-HSD. The purified enzyme was characterized with respect to kinetic parameters, substrate specificity and localization. The function of the enzyme in steroid metabolism is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0173-0835
    Keywords: In-gel digestion ; Automation ; Peptide elution ; In-line column adapter ; Protein sequencing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: An improved method for the generation and automated isolation of internal peptides by in situ gel digestion of electrophoretically separated proteins is described [1]. To enhance the sensitivity of the method, and to reduce the amount of sample handling steps, we have automated the extraction procedure of peptides after protein cleavage in a sodium dodecyl sulfate (SDS) gel matrix. The excised protein-containing polyacrylamide bands or spots are first minced to defined particles of about 30 μm. After in situ gel digestion, the gel slurry is transferred into a mini reversed-phase column-funnel assembly in the sample loading station of the Hewlett-Packard protein sequencer. Applying nitrogen pressure elutes peptides from the gel slurry onto the reversed-phse material. The mini reversed-phase column is then placed in an in-line column adapter and connected to a micropreparative high performance liquid chromatography (HPLC) column, where separation of the peptides under standard conditions is achieved. In the work described here complete digestions and excellent peptide recoveries allowed the generation of extensive internal sequence information from low picomole amounts of proteins. The method has been routinely applied in both laboratories for two yearsPart of the results were presented as a poster at the Protein Society Meeting 1994 in San Diego..
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0173-0835
    Keywords: Mass determination ; Matrix-assisted laser desorption ionization-mass spectrometry ; Electroblotting ; Protein ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Direct mass spectrometric analysis of proteins electroblotted onto polyvinylidene fluoride membranes after sodium dodecyl sulfate-polyacrylamide gel electrophoresis is demonstrated by matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) with a linear time-of-flight instrument, equipped with a nitrogen laser (337 nm). The blotted proteins were desorbed directly from the blotting membrane after incubation with sinapinic acid as matrix. Different commercially available membranes resulted in high quality protein signals for hydrophobic membranes exhibiting high specific surface areas (Immobilon PSQ or Trans-Blot) or for charged membranes (Immobilon CD). Systematic investigations with standard proteins were performed to compare standard preparation procedures for ultraviolet (UV) MALDI-MS on stainless steel sample stages and preparation of proteins immobilized onto membranes either by direct application from protein solutions (spotting) or by electrotransfer from gels (electroblotting). Aspects such as mass resolution, reproducibility from shot to shot and spot to spot, mass accuracy, and preservation of protein localization are addressed in this paper.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0173-0835
    Keywords: Matrix assisted laser desorption ; ionization - mass spectrometry ; Suppression effects ; Enzymatic sequencing ; Peptide sequencing ; Ladder sequencing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The techniques of enzymatic and chemical peptide ladder sequencing, coupled with ultraviolet - matrix assisted laser desorption/ionization - mass spectrometry (UV-MALDI-MS) have been improving continuously in the last five years and have now become important tools for primary structure identification. In this work, signal suppression effects, appearing in UV-MALDI-MS (excitation 337 nm) of ladder peptides, were investigated using the 17-amino acid peptide dynorphin A. We show, with examples of simple “two-peptide” systems and more complex “multi-peptide” systems, that suppression effects do in fact exist. The magnitude of the observed suppression is strongly dependent upon both the nature and the amount of the suppressing peptide. Suppression behavior of individual ladder peptides was investigated on equimolar mixtures of ten ladder peptides. Significant signal suppression was recorded for all ladder peptides, with some of them being approximately 170 times lower in signal intensity than the pure, i.e., unsuppressed peptide at the same concentration. For the investigated system  -  dynorphin A, 4-hydroxy-α-cyanocinnamic acid (4-HCCA) matrix, UV excitation  -  a correlation between the extent of suppression and an intractable combination of peptide hydrophobicity and the presence of several basic amino acids can be seen.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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