Synthesis and secondary structure of oligo(alpha-isobutyl beta,L-aspartate)s.
The oligo(beta-peptide)s, hexa(alpha-isobutyl beta,L-aspartate) (Hex-AIBLA) and octa(alpha-isobutyl beta,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(beta-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 3(14) 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.
García-Martín
M G
MG
Departamento de Química Orgánica y Farmacéutica, Universidad de Sevilla, Facultad de Farmacia, 41071 Sevilla, Spain.
García-Alvarez
M
M
Martínez de Ilarduya
A
A
Campos
L
L
Galbis
J A
JA
Muñoz-Guerra
S
S
D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D019906:Nuclear Magnetic Resonance, Biomolecular; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D017433:Protein Structure, Secondary; D012996:Solutions / Q000737:chemistry; D013696:Temperature
D009842:Oligopeptides; D012996:Solutions; C500053:hexa(alpha-isobutyl beta-aspartate); C500054:octa(alpha-isobutyl beta-aspartate)