title: Effects of fluidity on the ensemble structure of a membrane embedded α-helical peptide.
abstract: Melittin, the main hemolytic component of honeybee venom, is unfolded in an aqueous environment and folds into an α-helical conformation in a lipid environment. Membrane fluidity is known to affect the activity and structure of melittin. By combining two structurally sensitive optical methods, circular dichroism (CD) and deep-ultraviolet resonance Raman spectroscopy (dUVRR), we have identified distinct structural fluctuations in melittin correlated with increased and decreased 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayer fluidities. CD spectra have reduced intensity at temperatures above 22°C and high concentrations of the cholesterol analog 5α-cholestan-3β-ol indicating distortions in the α-helical structure under these conditions. No increase in the amide S is observed in the temperature-dependent dUVRR spectra, suggesting an increase in 310 -helical structure with increasing temperatures above 22°C. However, incorporation of 25 mol% 5α-cholestan-3β-ol resulted in a small increase in the amide S intensity indicating partial unfolding of melittin.
authors.affiliation: Department of Chemistry, University of Missouri, 601 S College Ave, 125 Chemistry Building, Columbia, MO, 65211.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Eagleburger
authors.forename: Jason W
authors.initials: JW
authors.lastname: Cooley
authors.forename: Renee D
authors.initials: RD
authors.lastname: JiJi
mesh_terms: D016880:Anisotropy; D002942:Circular Dichroism; D008081:Liposomes / Q000737:chemistry*; D008555:Melitten / Q000737:chemistry*; D008560:Membrane Fluidity; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence; D013059:Spectrum Analysis, Raman; D013696:Temperature
chemical_list: D008081:Liposomes; D008555:Melitten
keywords: circular dichroism; deep-UV resonance Raman spectroscopy; melittin; membrane