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Fourier transform infrared spectroscopic studies of polypeptides and membrane-associated proteins

Kennedy, Dorian Francis; (1991) Fourier transform infrared spectroscopic studies of polypeptides and membrane-associated proteins. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Fourier transform infrared (FTIR) spectroscopy has been used to investigate the interaction of polypeptides and proteins with model biomembranes. The characterisation of peptides known to possess a structure, or mixed α-/β-helical structures, was carried out. Fully stable β-helices in organic solvent were found to absorb IR radiation in the 1666-1662 cm-1 range. Peptides known to contain both α- and β-helical structures exhibit IR absorption bands characteristic of both structures. Peptides containing β-helical structure in organic solvent altered their structure in aqueous lipid dispersion to become predominantly α-helical. Peptides containing mixed α- and β-helices in organic solvent also altered their structure on interaction with lipids, and formed aqueous channels in the membrane. Peptides known to fold into the β-bend ribbon structure in organic solvent showed an amide I band maxima at 1648-1645 cm-1 β-bend ribbon peptides were largely unaltered by the membrane environment, but formed aqueous pores in the membrane. The mechanism of spontaneous insertion of soluble proteins into model membranes was investigated using colicin A and aerolysin. The secondary structure of colicin A remained α-helical on insertion into the membrane but it adopted a more open configuration. Aerolysin and its precursor, proaerolysin, contain predominantly β-sheet structure with a small region of hydrophobic α-helix in their soluble form. An increase in α-helical content was observed when aerolysin interacted with model membranes. The structure of phospholipase A2's from different sources contained a high degree of conformational homology. Conformational changes consistent with an increase α-helix and a decrease in β-sheet, and possibly β-turns, were observed on binding to lipids and a transition-state inhibitor in micellar form.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Fourier transform infrared spectroscopic studies of polypeptides and membrane-associated proteins
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/10116690
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