4,4(')-Dianilino-1,1(')-binaphthyl-5,5(')-disulfonate: report on non-beta-sheet conformers of Alzheimer's peptide beta(1-40).
The venerable fluorescent probe of protein hydrophobic regions, 4,4(')-dianilino-1,1(')-binaphthyl-5,5(')-disulfonate (bis-ANS), unexpectedly increases in fluorescence with soluble beta(1-40) in acidic buffer solutions but reacts weakly with amyloid fibrils while other hydrophobic probes react with the fibrils. CD analysis correlates reaction with the probe with random coil/mixed conformations and alpha-helical forms of beta(1-40) in buffer solutions but less so with soluble beta-sheet forms or amyloid fibrils. The kinetics of the fluoroalcohol-induced interconversion of conformers can be followed by changes in bis-ANS fluorescence. Formation of the beta-sheet form in aqueous buffer is limited by a slow component (minutes) while fluoroalcohol-promoted changes between beta-sheet and alpha-helix occur over seconds. Variants of beta(1-40) such as beta(1-42) or the Dutch E22Q mutation of beta(1-40) and fragments beta(1-28), beta(12-28), beta(10-20 amide), and beta(10-35 amide) react with bis-ANS under conditions that do not support fibril formation. Primary amino acid sequence is important as beta(1-11) does not cause bis-ANS fluorescence while beta(1-16) does, but hydrophobicity is not as beta(25-35) and beta(15-20 amide) are unreactive. bis-ANS is a useful biophysical tool for characterizing particular, but not all, soluble Abeta conformations distinct from the fibrillar form of amyloid peptides detected by Thioflavin T.
LeVine
Harry
H
CNS Pharmacology, Pfizer Global Research and Development, Ann Arbor, MI 48105, USA. Harry.Levine@pfizer.com
D000544:Alzheimer Disease / Q000378:metabolism; D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000235:genetics; D000817:Anilino Naphthalenesulfonates; D005456:Fluorescent Dyes; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012995:Solubility; D013050:Spectrometry, Fluorescence
D016229:Amyloid beta-Peptides; D000817:Anilino Naphthalenesulfonates; D005456:Fluorescent Dyes; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); C035763:5,5'-bis(8-(phenylamino)-1-naphthalenesulfonate)