Biomimetic Nanostructures Based on Enforced Folding and Assembly

摘要

@@ The folding and further assembly of protein leads to dazzling arrays of structures with different complexities. Since the mid-1990s, the structural and functional diversities of protein structures have inspired the creation of many unnatural folding oligomers, I.e., foldamers[1'6]. The first examples of foldamers are peptidomimetic oligomers including the helical β-peptides reported by Gellmam[7] and Seebach[8], and the oligo(aminoxy acids) reported by Yang and Wu[9]. Since these early reports, numerous peptidomimetic foldamers, such as γ-peptides, δ-peptides, and many other folding unnatural oligomers, have been described. The majority of these peptidomimetic foldamers adopt tightly packed helical conformation with no internal void. In contrast, void-containing molecular and especially supramolecular structures are commonplace in nature. For example, gramicidin A, a naturally occurring antibiotic peptide consisting of alternating D and L amino acid residues, adopts a β-helical conformation containing a small (-4 A across) hydrophilic internal pore that, upon dimerization within lipid bilayers, allows monovalent cations and water to pass[10]. Α-Hemolysin assembles into a heptameric aggregate containing a large (14-16 A across) hydrophilic pore that spans cell membranes and cause cell death by non-selectively passing various ions and small molecules[11]. Other void-or pore-containing molecular and supramolecular structures formed by the folding and assembly of proteins include highly selective ion[12] or water channels[13] or the tubular capsid of tobacco mosaic virus[14]. The structures and functions of biological pores and channels have inspired the creation of void-containing synthetic molecules and/or their corresponding assemblies. In addition to mimicking the fascinating features of biological porous structures, synthetic architectures possess their own unique advantages, such as reduced structural complexities, improved thermal and mechanical stability, as well as compatibility with both natural and unnatural media.