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Structural analysis of thermally inactivated nisin

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dc.contributor.advisor Daeschel, Mark A.
dc.creator Musafija-Jeknic, Tamara
dc.date.accessioned 2012-10-25T17:36:29Z
dc.date.available 2012-10-25T17:36:29Z
dc.date.copyright 1996-01-12
dc.date.issued 1996-01-12
dc.identifier.uri http://hdl.handle.net/1957/34669
dc.description Graduation date: 1996 en_US
dc.description.abstract Nisin, an antimicrobial peptide used in food preservation was evaluated for thermal stability. Nisin retained antimicrobial activity after having been heated at 121°C for seven hours. Anhydrous nisin and concentrated nisin solutions (5-10 mg/ml) were still active after having been heated up to 190°C or 230°C. When exposed to high temperatures of 200 or 250°C for up to one hour, nisin lost all antimicrobial activity. After 3.5 hours of heating at 121°C an inactive nisin degradation product, designated nisin L, was isolated. In comparison to native nisin, nisin L had reduced activity against Pediococcus pentosaceus FBB-61 and no activity against Bacillus cereus T vegetative cells or spores. Structural changes to nisin L were studied by high performance liquid chromatography (HPLC), ion spray mass spectroscopy (MS), ¹H nuclear magnetic resonance spectroscopy (NMR) and circular dichroism (CD) spectroscopy and compared to original nisin. There was no difference in molecular weight between nisin and nisin L. Both MS spectra contained nisin, with average molecular weight (MW) of 3354 daltons (D), and hydrated nisin with average molecular weight of 3372 D. Nisin L had higher proportion of hydrated molecules, and it had molecules with more then one water addition. Proton NMR analysis of nisin L indicated that dehydrobutyrine 2 and dehydroalanine 5 residues had been altered, and that several new hydrogen resonances appeared. Water additions in nisin L are likely to have occurred at dehydroresidues, making them inactive. Nisin L was found to be more polar, as would be expected for a more hydrated peptide. Analysis of CD spectra indicated that nisin L had smaller content of a helix and therefore lesser membrane spanning capability. Tandem mass spectroscopy of original nisin revealed that it was hydrated at lysine 34 residue. en_US
dc.language.iso en_US en_US
dc.subject.lcsh Nisin -- Thermal properties en_US
dc.subject.lcsh Nisin -- Spectra en_US
dc.title Structural analysis of thermally inactivated nisin en_US
dc.type Thesis/Dissertation en_US
dc.degree.name Master of Science (M.S.) in Microbiology en_US
dc.degree.level Master's en_US
dc.degree.discipline Science en_US
dc.degree.grantor Oregon State University en_US
dc.contributor.committeemember Anderson, Sonia R.
dc.contributor.committeemember Stone, Jeffrey K.
dc.description.digitization File scanned at 300 ppi (Monochrome, 8-bit Grayscale, 24-bit Color) using ScandAll PRO 1.8.1 on a Fi-6670 in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR. en_US
dc.description.peerreview no en_us

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