Giant amino acids designed on the polysaccharide scaffold and their protein-like structural interconversion

Abstract

Amphoteric β-1,3-glucans possessing both amino groups and carboxylic acid groups on the C6 positions of glucose units were designed and synthesized from naturally produced curdlan. The amphoteric polysaccharides showed the isoelectric point and the pH responsive interconversion between the original triple helix and single-stranded random structures. Since the pH dependences are comparable to the typical properties of proteins, the polysaccharides can be considered as a new class of giant amino acids. Utilizing the pH responsiveness, pH-controlled catch-and-release has been realized for cationic peptides or anionic DNA. We believe that the amphoteric polysaccharide can act as a new potential polymer to construct stimuli-responsive smart materials on the basis of the polysaccharide scaffold.

Regioselective synthesis of cationic 6-deoxy-6-(N,N,N-trialkylammonio)curdlan derivatives

“…Cationic polysaccharides are materials of interest for a number of applications, ranging from industrial (e.g., flocculants (Pal, Mal & Singh, 2005) and anti-bacterial coatings (Dilamian, Montazer & Masoumi, 2013)) to biomedical (e.g., vehicles for gene delivery (Ikeda, Minari, Shimada, Numata, Sakurai & Shinkai, 2007;Mai, Zhang, Liang, Gao, Du & Zhang, 2015) and for delivery of anionic drugs (Bernkop-Schnurch & Dunnhaupt, 2012;Tamaru, Tokunaga, Hori, Matsuda & Shinkai, 2014)). Despite the potential utility of such materials, there are relatively few synthetic approaches to cationic polysaccharides, especially to those that carry a permanent positive charge (and thus are charged even at neutral pH).…”

Protein‐Mimicking Functions of Nano‐Size Monoamido Amino Acids Derived from Polysaccharides of Marine Origin

“…The optical rotatory dispersion (ORD) measurements were done in different pHs to see the structural folding/unfolding of Alg‐EDA (Figure S10, Supporting Information). Alg‐EDA also showed no ORD maximum in the 200–600 nm wavelength region indicating the formation of single‐stranded structural formations in Alg‐EDA, exhibiting no sign of formation of the helical structure . Alg‐EDA displayed random coil (single‐stranded) structures over the region pH 2.0–12.0.…”

“…AEAm and AECAm showed no ORD maximum in the 200–600 nm wavelength region. It suggested that there were single‐stranded structural formations in AEAm and AECAm, and no evidence of helical structure being formed . AEAm and AECAm exhibited random coil (single‐stranded) structures over the region pH 2.0–12.0.…”

“…It has been demonstrated that seaweed polysaccharides including agarose, a linear polymer of 1,3‐linked d ‐galactopyranose and 1,4‐linked 3,6‐anhydro‐ l ‐glactopyranose, can be variously derivatized imparting new properties, for example, protein‐like behavior, pH‐responsive, fluorogenic, self‐assembled nano‐material properties as well as for its use in smart drug delivery applications . Present study deals with three monoamido amino acids based on agarose derivatives of 1,6‐hexamethylene‐ and 1,4‐cyclohexyl diamines resembling glycoconjugates as well as alginic acid amide of ethylenediamine.…”

pH‐Responsive Fluorescence Change Based on Dynamic Exchange between Emitting Aggregates and Quenching Monomers in Donor–Acceptor Dyes Bearing Carboxylic Acid Groups

“…At lower pH, the aggregate bearing the carboxylic acid group in its neutral, protonated form is preserved and shows light emission. In contrast, at higher pH, the aggregate dissociates to the monomer due to electrostatic repulsion among the anionic carboxylate moieties generated from the protonation/deprotonation equilibrium, leading to a pH‐responsive change between the emitting aggregate and the quenching monomer (Figure ). The parent donor–acceptor dye has two additional advantages: a longer‐wavelength red‐light emission inside the biological optical window for lower interference from background fluorescence, and a large Stokes shift for minimizing reabsorption of emitted red‐light fluorescence .…”