title: Structural diversity of alpha-amino acid based layer-block dendrons and their layer-block sequence-dependent gelation properties.
abstract: A library of G1-G3 alpha-amino acid based layer-block dendrons 1-6 containing different amino acid residues in the different concentric layers was prepared by solution-phase peptide synthesis. The structures of these dendrons were characterized by 1H and 13C NMR spectroscopy and, except for the G3 series of compounds, by mass spectrometry. The purities of these compounds were also determined by size-exclusion chromatography. Owing to the presence of a large number of amide groups, these dendrons exhibit unusually strong self-aggregating properties in both polar and nonpolar solvents. Some of these dendrons are found to be extremely good organogelators towards aromatic solvents with minimum gel concentrations approaching 4 mg mL(-1). Their gelation ability is found to be highly dependent on the nature of the amino acid compositions, the amino acid layer-block sequence within the dendritic architecture and the nature of the focal-point functionality. IR spectroscopic analysis indicates that gelation is induced by intermolecular hydrogen bonds. Circular dichroism studies suggest the formation of hierarchical chiral structures in the gel state, although the existence of chiral morphologies could not be observed by scanning electron microscopy.
authors: Department of Chemistry and Materials Science and Technology Research Center, Institute of Science and Technology, Chinese University of Hong Kong, Shatin, NT, SAR, Hong Kong. hfchow@cuhk.edu.hk
authors: Hak-Fun
authors: HF
authors: Chow
authors: Jie
authors: J
authors: Zhang
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D000873:Anthracenes / Q000737:chemistry*; D002850:Chromatography, Gel; D002942:Circular Dichroism; D005782:Gels / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008855:Microscopy, Electron, Scanning; D008958:Models, Molecular; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000596:Amino Acids; D000873:Anthracenes; D005782:Gels; C501244:dendron