Structural transitions involved in a novel amyloid-like β-sheet assemblage of tripeptide derivatives
✍ Scribed by S. Ganesh; R. Jayakumar
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 2003
- Tongue
- English
- Weight
- 167 KB
- Volume
- 70
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Abstract
Self‐assembly of two tripeptide derivatives containing three nonpolar isoleucine moieties and polar oxyethylene groups are studied in methanol. Peptide A [CH~3~(OCH~2~CH~2~)~3~OCH~2~CO(Ile)~3~OCH~3~] and peptide B [CH~3~(OCH~2~CH~2~)~3~OCH~2~CO(Ile)~3~NH (CH~2~CH~2~O)~3~CH~3~] take a mixture of unordered and helical conformation at low concentration (8.5×10^−4^M). However, at high concentration (2×10^−3^M), both the peptide showed significant increase in the helical conformation. An interesting conformational transition of peptides A and B at various methanol contents was observed in the solvated films of these compounds by spectroscopic methods like the far‐uv circular dichroism and Fourier transform infrared (FT‐IR) techniques. Peptide B, which contains more polar oxyethylene groups than A, showed a highly cooperative conformational transition when the methanol content was decreased. This transition was characterized by a large increase of β‐sheet, retaining a α‐helical contribution. Peptide A showed a conformational transition resulting in a β‐sheet in the aggregated state. From the CD spectra, the ratio in the ellipticity indicates that peptide B forms twisted antiparallel β‐sheet conformation, whereas peptide A takes a parallel β‐sheet conformation. The results obtained in this work indicates the role of polar derivatization on the conformational preference of peptides having similar sequence. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 336–345, 2003