Not All β-Sheets Are the Same: Amyloid Infrared Spectra, Transition Dipole Strengths, and Couplings Investigated by 2D IR Spectroscopy.

ABSTRACT: We report the transition dipole strengths and frequencies of the amyloid β-sheet amide I mode for the aggregated proteins amyloid-β_1-40, calcitonin, α-synuclein, and glucagon. According to standard vibrational coupling models for proteins, the frequencies of canonical β-sheets are set by their size and structural and environmental disorder, which determines the delocalization length of the vibrational excitons. The larger the delocalization the lower the frequency of the main infrared-allowed transition, A_⊥. The models also predict an accompanying increase in transition dipole strength. For the proteins measured here, we find no correlation between transition dipole strengths and amyloid β-sheet transition frequency. To understand this observation, we have extracted f

SUBMITTER: Lomont JP 

PROVIDER: S-EPMC5705941 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature