Columnar assembly of cyclic beta-amino acid functionalized with pyranose rings.
A novel cyclic trimer and tetramer of protected beta-glycamino acids were synthesized and investigated on conformation and assembly formation. A characteristic point of these cyclic beta-glycamino acids is their better solubility than other cyclic beta-amino acids due to the pyranose rings. Thus, the assembling process of the cyclic molecules could be examined by CD or NMR spectroscopy. FT-IR and NMR measurements and geometry optimization revealed a highly symmetric and planar conformation for each cyclic beta-peptide with all-trans amide groups. The amide groups in the cyclic peptides took a vertical orientation against the cyclic skeleton to be suitably arranged for intermolecular hydrogen bonds, which should promote formation of molecular assembly in a columnar structure through molecular stacking. These cyclic beta-peptides were successfully crystallized to yield rod-shaped molecular assemblies in nanometer sizes. Evidence for the columnar structure in the crystals was obtained by electron diffraction analysis, which showed a layer spacing of ca. 4.8 A. Interestingly, the molecular assembly of the cyclic trimer showed a high aspect ratio, width less than 40 nm, and length more than 2 mum, suggesting stable molecular stacking in the column.
Fujimura
Futoshi
F
Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
Hirata
Tatsuya
T
Morita
Tomoyuki
T
Kimura
Shunsaku
S
Horikawa
Yoshiki
Y
Sugiyama
Junji
J
D000596:Amino Acids / Q000737:chemistry*; D002942:Circular Dichroism; D006860:Hydrogen Bonding; D015394:Molecular Structure; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
D000596:Amino Acids; D010456:Peptides, Cyclic