title: Synchrotron radiation circular dichroism spectroscopy applied to metmyoglobin and a 4-alpha-helix bundle carboprotein.
abstract: The novel technique, synchrotron radiation-based circular dichroism (SR-CD), has been applied to the study of metmyoglobin and a carboprotein (carbohydrate-based peptide with protein tertiary structure) with 4-alpha-helix bundle structure, as well as a carbopeptide (carbohydrate-based peptide) with a truncated peptide sequence. The use of synchroton radiation (SR) enabled circular dichroism (CD) measurements in the vacuum ultraviolet (VUV) down to 168 nm in D(2)O and 160 nm in 2,2,2-trifluoroethanol (TFE). The band shape in the CD spectra in the low wavelength region was studied, comparing samples with two types of alpha-helical tertiary structure, namely the globin fold and the 4-alpha-helix bundle motif. No significant differences were found between the CD spectra of the alpha-helical samples (metmyoglobin and carboprotein) in D(2)O solution. The use of 2,2,2-TFE (TFE) as solvent clearly alters the VUV CD but the two samples have very similar CD spectra. The solvent-induced denaturing of metmyoglobin in TFE was observed using absorption and CD spectroscopy of the Soret band, with results indicating heme release. The VUV spectrum of TFE-denatured metmyoglobin exhibits dramatic differences in comparison with previous studies of the native enzyme in aqueous solution. The implications of this observation are discussed.
authors.affiliation: Department of Natural Sciences, Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark. pwt@kvl.dk
authors.forename: Peter W
authors.initials: PW
authors.lastname: Thulstrup
authors.forename: Jesper
authors.initials: J
authors.lastname: Brask
authors.forename: Knud J
authors.initials: KJ
authors.lastname: Jensen
authors.forename: Erik
authors.initials: E
authors.lastname: Larsen
mesh_terms: D000818:Animals; D002942:Circular Dichroism; D005690:Galactose / Q000031:analogs & derivatives* / Q000737:chemistry; D006736:Horses; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008786:Metmyoglobin / Q000737:chemistry* / Q000187:drug effects; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012997:Solvents; D013056:Spectrophotometry, Ultraviolet; D017356:Synchrotrons; D014270:Trifluoroethanol / Q000494:pharmacology; D014867:Water / Q000737:chemistry
chemical_list: D010455:Peptides; D012997:Solvents; C469243:methyl-galactopyranoside; D014867:Water; D008786:Metmyoglobin; D014270:Trifluoroethanol; D005690:Galactose