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Unformatted text preview: Biological Sciences 110a, Fall 2011 Lecture Outline #8: Membrane structure and function reading: Sections 4.2, 4.4, 4.5, 4.6 Membrane proteins integral transmembrane require detergents or organic solvents to remove from membrane transmembrane segments: alpha-helical (many examples) or beta-barrel (e.g. porins) about 20 amino acids required to cross the hydrophic core of a membrane in the alpha- helical conformation (30 Å) can predict transmembrane segments in amino acid sequences - calculate hydrophobicity for 20-residue sequences - hydropathy plots (e.g. text Fig. 4-20 (4-18)) peripheral easily removed from membrane - e.g. by high salt solutions, acids or bases lipid-anchored hydrocarbon anchors fatty acid anchors glycolipid anchors (GPI anchors) Membrane properties sheets 60 - 100 Å thick ¡uid mosaics two-dimensional solution of proteins in lipids lipids function as a solvent within the membrane, as a barrier across the membrane proteins never ¡ip orientation, lipids very rarely (except cholesterol)...
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- Fall '08