title: Pressure-induced transformation of alpha-helix to beta-sheet in the secondary structures of amyloid beta (1-40) peptide exacerbated by temperature.
abstract: The effect of pressure on the conformational structure of amyloid beta (1-40) peptide (A beta(1-40)), exacerbated with or without temperature, was determined by Fourier transform infrared (FT-IR) microspectroscopy. The result indicates the shift of the maximum peak of amide I band of intact solid A beta(1-40) from 1655 cm(-1) (alpha-helix) to 1647-1643 cm(-1) (random coil) with the increase of the mechanical pressure. A new peak at 1634 cm(-1) assigned to beta-antiparallel sheet structure was also evident. Furthermore, the peak at 1540 cm(- 1) also shifted to 1527 (1529) cm(-1) in amide II band. The former was assigned to the combination of alpha-helix and random coil structures, and the latter was due to beta-sheet structure. Changes in the composition of each component in the deconvoluted and curve-fitted amide I band of the compressed A beta(1-40) samples were obtained from 33% to 22% for alpha-helix/random coil structures and from 47% to 57% for beta-sheet structure with the increase of pressure, respectively. This demonstrates that pressure might induce the conformational transition from alpha-helix to random coil and to beta- sheet structure. The structural transformation of the compressed A beta(1-40) samples was synergistically influenced by the combined effects of pressure and temperature. The thermal-induced formation of beta-sheet structure was significantly dependent on the pressures applied. The smaller the pressure applied the faster the beta-sheet structure transformed. The thermal-dependent transition temperatures of solid A beta(1-40) prepared by different pressures were near 55-60 degrees C.
authors.affiliation: Biopharmaceutics Laboratory, Department of Medical, Research and Education, Veterans General Hospital-Taipei, 201 Shih-Pai Road, Sec. 2, Taipei 11217, Taiwan R.O.C. sylin@vghtpe.gov.tw
authors.forename: Shan-Yang
authors.initials: SY
authors.lastname: Lin
authors.forename: Horng-Lun
authors.initials: HL
authors.lastname: Chu
authors.forename: Yen-Shan
authors.initials: YS
authors.lastname: Wei
mesh_terms: D000577:Amides / Q000737:chemistry; D016229:Amyloid beta-Peptides / Q000737:chemistry*; D010446:Peptide Fragments / Q000737:chemistry*; D011312:Pressure; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics
chemical_list: D000577:Amides; D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40)