Characterization of intermolecular structure of β2- microglobulin core fragments in amyloid fibrils by vacuum-ultraviolet circular dichroism spectroscopy and circular dichroism theory

Koichi Matsuo*, Hirotsugu Hiramatsu, Kunihiko Gekko, Hirofumi Namatame, Masaki Taniguchi, Robert W. Woody

*Corresponding author for this work

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Intermolecular structures are important factors for understanding the conformational properties of amyloid fibrils. In this study, vacuum-ultraviolet circular dichroism (VUVCD) spectroscopy and circular dichroism (CD) theory were used for characterizing the intermolecular structures of β2- microglobulin (β2m) core fragments in the amyloid fibrils. The VUVCD spectra of β2m20-41, β2m 21-31, and β2m21-29 fragments in the amyloid fibrils exhibited characteristic features, but they were affected not only by the backbone conformations but also by the aromatic side-chain conformations. To estimate the contributions of aromatic side-chains to the spectra, the theoretical spectra were calculated from the simulated structures of β2m21-29 amyloid fibrils with various types of β-sheet stacking (parallel or antiparallel) using CD theory. We found that the experimental spectrum of β2m21-29 fibrils is largely affected by aromatic-backbone couplings, which are induced by the interaction between transitions within the aromatic and backbone chromophores, and these couplings are sensitive to the type of stacking among the β-sheets of the fibrils. Further theoretical analyses of simulated structures incorporating mutated aromatic residues suggested that the β2m21-29 fibrils are composed of amyloid accumulations in which the parallel β-sheets stack in an antiparallel manner and that the characteristic Phe-Tyr interactions among the β-sheet stacks affect the aromatic-backbone coupling. These findings indicate that the coupling components, which depend on the characteristic intermolecular structures, induce the spectral differences among three fragments in the amyloid fibrils. These advanced spectral analyses using CD theory provide a useful method for characterizing the intermolecular structures of protein and peptide fragment complexes.

Original languageEnglish
Pages (from-to)2785-2795
Number of pages11
JournalJournal of Physical Chemistry B
Volume118
Issue number11
DOIs
StatePublished - 20 Mar 2014

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