Synthesis and secondary structure of oligo(α‐isobutyl β,L‐aspartate)s

• Published in: Biopolymers Vol. 77; no. 2; pp. 121 - 127
• Main Authors: García‐Martín, M. G., García‐Alvarez, M., Martínez de Ilarduya, A., Campos, L., Galbis, J. A., Muñoz‐Guerra, S.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 05-02-2005
• Subjects: Circular Dichroism; circular dichronism; conformation; Crystallography, X-Ray; NMR; Nuclear Magnetic Resonance, Biomolecular; oligo(β‐aspartate); oligo(β‐peptide); Oligopeptides - chemical synthesis; Oligopeptides - chemistry; poly(β‐aspartate); poly(β‐peptide); Protein Structure, Secondary; Solutions - chemistry; Temperature; x‐ray diffraction
• ISSN: 0006-3525; 1097-0282
• DOI: 10.1002/bip.20191

The oligo(β‐peptide)s, hexa(α‐isobutyl β,L‐aspartate) (Hex‐AIBLA) and octa(α‐isobutyl β,L‐aspartate) (Oct‐AIBLA), were synthesized in solution by using standard coupling methods. Powder x‐ray diffraction showed that the octamer crystallized in the two helical crystal forms known to exist in the homologous poly(β‐peptide), whereas the hexamer seemed to adopt an extended conformation. Both CD and 1H‐NMR spectra of Oct‐AIBLA in MeOH revealed the presence of a regularly folded conformation in this solvent, presumably the 314 helix. The helix‐to‐coil transition of Oct‐AIBLA was observed to take place upon heating in both MeOH and CHCl3, in the second case associated with a not‐well‐defined aggregation–disaggregation process. The spectroscopic evidence obtained on the presence of folded structures in Hex‐AIBLA were much weaker than for the octamer. © 2005 Wiley Periodicals, Inc. Biopolymers, 2005