Secondary conformations and temperature effect on structural transformation of amyloid beta (1-28), (1-40) and (1-42) peptides.
Secondary structure of three amyloid b-peptides [A beta(1-28), A beta(1-40) and A beta(1-42)] in the solid state was respectively determined by Fourier transform infrared (FT-IR) microspectroscopy. Their thermal-dependent structural transformation were also investigated by FT-IR microspectroscopy equipped with a thermal analyzer. The present result demonstrates that the solid-state A beta(1-28), A beta(1-40) and A beta(1-42) peptides showed a significant IR spectral difference in the amide I and II bands. The secondary conformation of A beta(1-28) peptide was the combination of major beta-sheet and minor alpha-helix with little random coil structures, but A beta(1-40) peptide showed the co-existence of major beta-sheet and minor random coil with little alpha-helix structures. A beta(1-42) peptide mainly consisted of the predominant b-sheet structure. Although the intact A beta(1-28), A beta(1-40) or A beta(1-42) peptide exhibits a different secondary structure, a similar beta-conformation may form after thermal treatment. A thermal-dependent transition was found for solid A beta(1-28) and A beta(1-40) peptides near 40 degrees C and 45 degrees C, respectively. There was no transition temperature for solid A beta(1-42) peptide, however, due to only a very little level of alpha-helix and random coil structure containing in the solid A beta(1-42) peptide. The thermal denaturation plays an important role in the structural transformation from alpha-helix/random coil to beta-sheet.
Lin
Shan-Yang
SY
Biopharmaceutics Laboratory, Department of Medical Research and Education, Veterans General Hospital-Taipei, Taipei, Taiwan. sylin@vghtpe.gov.tw
Chu
Horng-Lun
HL
Wei
Yen-Shan
YS
D016229:Amyloid beta-Peptides / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D006801:Humans; D010446:Peptide Fragments / Q000737:chemistry*; D017433:Protein Structure, Secondary; D012984:Software; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; C084358:amyloid beta-protein (1-28); C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42)