Molecular assembly formation of cyclic hexa‐β‐peptide composed of acetylated glycosamino acids

Abstract

A novel cyclic hexamer of acetylated β‐glycosamino acid was synthesized and its conformation and molecular assembly formation was investigated. Variable temperature NMR study indicated that the cyclic hexapeptide took a C3 symmetric conformation at room temperature, but at elevated temperatures a C6 symmetric one, which was not due to averaging of the C3 symmetric conformation, appeared. Computational geometry optimization showed that the C6 symmetric conformation was a highly planar structure with amide groups orienting perpendicular to the ring plane. The cyclic hexa‐β‐peptide formed rod‐shaped crystals from an N,N‐dimethyl formamide solution at elevated temperature. The optical microscopy observation with a sensitive tint plate under cross‐nicol configuration and electron diffraction analysis of the crystals revealed that the cyclic hexa‐β‐peptides were stacked one after the other to form a regular nanotube structure. © 2007 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 88: 150–156, 2007. This article was originally published online as an accepted preprint. The ‘Published Online’ date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

Peptide nanotube aligning side chains onto one side

“…The electron diffraction patterns were obtained with these crystals, indicating the spacings of 4.9 Å and 4.8 Å respectively for CP5ES and CP3 along the long axis of the needle-like molecular assemblies ( Figure S2). These spacings are agreeable with the distance between cyclic β-peptides in PNTs as reported previously [6,[9][10][11]. CP5ES and CP3 can therefore self-assemble into PNTs, which bundle together to grow into the needle-and rod-like crystals.…”

“…A sharp N–H stretching peak (amide A band) appears at 3309 cm −1 , supporting that all the amide protons are involved in hydrogen bond formation and their environment is highly homogeneous. The IR analysis therefore supports the PNT formation .…”

Peptid‐Nanoröhren

“…Vernetzen des gebundenen WGA‐Lectins ermöglicht das Wegwaschen des “Gerüsts” aus cyclischen Tri‐β‐peptiden, wodurch eine Protein‐Nanoröhre zurückbleibt 20. Nanoröhren wurden auch für ein cyclisches Hexa‐β‐peptid aus acetylierten Glycosaminosäuren beobachtet, auch hier mit gut geordneten Ringstapeln 21…”

Artificial β-sheets: chemical models of β-sheets

“…Kimura and coworkers have reported parallel β-sheet stacking of cyclic β-peptides based on trans -2-aminocyclohexanecarboxylic acid and trans-pyranoid sugar amino acids in the solid state [44,45,46]; Chandrasekhar and coworkers have reported parallel β-sheet stacking of cyclic β-peptides based on cis-furanoid sugar amino acids in the solid state and in non-hydrogen-bonding solvents [47]. …”