title: Density functional theory analysis and spectral studies on amyloid peptide Abeta(28-35) and its mutants A30G and A30I.
abstract: Folding and self-assembly of amyloid beta (Abeta) peptide are linked to Alzheimer's disease. To understand the initial stage of amyloid-beta peptide aggregation, conformational characteristics of monomers of wild-type (WT) Abeta(28-35) and its mutant peptides A30G and A30I were investigated using density functional theory calculations and experimental studies. Monomeric structures and their relative stabilities were obtained on the basis of systematic structural optimization in the gas-phase and in the aqueous medium. Computations were performed by hybrid Hartree-Fock-Density Functional Theory (HF-DFT) at B3LYP/6-31G * level. Experimentally, the conformational transitions in the early stages of the octapeptide Abeta(28-35) and its mutants A30G and A30I in solution were characterized by CD, Thioflavin assay and FRET spectroscopy. Examination of the secondary structures revealed that Abeta(28-35) and its mutant monomers exist in random coil conformation in the aqueous medium in agreement with the theoretical predictions, which upon aging is transformed to sheet with different kinetics. This study deals with the structurally important intermediates and it may help to understand the mechanism of amyloid fibril aggregation leading to the onset of Alzheimer's disease.
authors.affiliation: Bio-Organic and Neurochemistry Laboratory, Central Leather Research Institute, Adyar, Chennai 600 020, India.
authors.forename: Sureshbabu
authors.initials: S
authors.lastname: Nagarajan
authors.forename: Jayakumar
authors.initials: J
authors.lastname: Rajadas
authors.forename: E J Padma
authors.initials: EJ
authors.lastname: Malar
mesh_terms: D000544:Alzheimer Disease / Q000209:etiology / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000235:genetics*; D052160:Benzothiazoles; D002942:Circular Dichroism; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes; D006801:Humans; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D066298:In Vitro Techniques; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry* / Q000235:genetics*; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics*; D011487:Protein Conformation; D055550:Protein Stability; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence; D055672:Static Electricity; D013816:Thermodynamics; D013844:Thiazoles
chemical_list: D016229:Amyloid beta-Peptides; D052160:Benzothiazoles; D005456:Fluorescent Dyes; D050505:Mutant Proteins; D010446:Peptide Fragments; D013844:Thiazoles; C009462:thioflavin T