Sequence-specific liquid crystallinity of collagen model peptides. I. Transmission electron microscopy studies of interfacial collagen gels
✍ Scribed by Regina Valluzzi; David L. Kaplan
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 2000
- Tongue
- English
- Weight
- 250 KB
- Volume
- 53
- Category
- Article
- ISSN
- 0006-3525
No coin nor oath required. For personal study only.
✦ Synopsis
The conformation, crystal structure and self-assembly behavior of three peptides with collagen-like repetitive sequences [(1) peptide GAPGPP: (Glu) 5 (Gly-Ala-Pro-Gly-Pro-Pro) 6 (Glu) 5 ; (2) peptide GVPGPP: (Glu) 5 (Gly-Val-Pro-Gly-Pro-Pro) 6 (Glu) 5 ; and (3) peptide GAPGPA: (Glu) 5 (Gly-Ala-Pro-Gly-Pro-Ala) 6 (Glu) 5 ] were compared. The peptides were characterized using transmission electron microscopy, electron diffraction, environmental scanning electron microscopy, and Fourier transform ir spectroscopy in order to determine how the molecular geometry dictated by each sequence affects the spontaneous generation of long-range ordered structures. Samples of each peptide, at ambient temperature and at 5°C, were examined as films dried from aqueous solution, air-water interfacial films, and chloroform-water interfacial films. Peptide GAPGPP prepared at 5°C and dried from bulk solution was found to have a collagen-like triple-helical structure. A sinusoidally textured gel, suggestive of cholesteric behavior was observed for peptides GAPGPP and GVPGPP at the aqueous chloroform interface at 5°C. Peptide GAPGPA also formed a gel, but less reproducibly and the sinusoidal texture was not as well defined. The periodicities of the sinusoidal textures were reproducibly 10 m for peptide GAPGPP, 7 m for peptide GVPGPP, and 6 m for peptide GAPGPA. The differences in the periodicity of the banded structure and in the crystallization behavior of the three peptides is attributed to differences in the symmetry of the preferred packing arrangement for each peptide, as evidenced by electron diffraction from crystallites that coexist with the sinusoidal gel. These differences are believed to be a measure of the effective symmetry and shape of the molecular cross section.