Dong-Sik Shin

Preparation of tri(ethylene glycol) grafted core-shell type polymer support for solid-phase peptide synthesis

A core‐shell type polymer support for solid‐phase peptide synthesis has been developed for high coupling efficiency of peptides and versatile applications such as on‐bead bioassays. Although various kinds of polymer supports have been developed, they have their own drawbacks including poor accessibility of reagents and incompatibility in aqueous solution. In this paper, we prepared hydrophilic tri(ethylene glycol) (TEG) grafted core‐shell type polymer supports (TEG SURE) for efficient solid‐phase peptide synthesis and on‐bead bioassays. TEG SURE was prepared by grafting TEG derivative on the surface of AM PS resin via biphasic diffusion control method and subsequent acetylation of amine groups which are located at the core region of AM PS resin. The performance of TEG SURE was evaluated by synthesizing several peptides. Three points can be highlighted: (1) easy control of loading level of TEG, (2) improved efficiency of peptide synthesis compared with the conventional resins, and (3) applicability of on‐bead bioassays.

Ultra-selective detection of Fe2+ ion by redox mechanism based on fluorescent polymerized dopamine derivatives

Polydopamine (PDA) is considered as a fluorescent molecule, however, the molecular structure and degree of polymerization that yield the most efficient fluorescence have yet to be identified. Here, we first present the fluorescence origin of polymerized dopamine derivatives (pDA) and their extraordinary behavior on the ultra-selective recognition of Fe2+ ions. Dopamine molecules are polymerized to 5,6-dihydroxyindole-rich pDA in basic conditions, followed by readily oxidizing to indole-5,6-quinone-rich pDA by dropping the pH to strongly acidic conditions. It was clearly demonstrated that oligomeric dopamine molecules were water-soluble with intense fluorescence (F-ODA, n = 3–4), while polymeric dopamine molecules were water-insoluble without fluorescence (PDA, n > 5). Also, F-ODA was dramatically selective to Fe2+ ions contradicting previous studies, and their unique binding mechanism was described through the redox potential analysis.

A phase-reversible Pd containing sphere-to-bridge-shaped peptide nanostructure for cross-coupling reactions

A sphere-to-bridge-shaped peptide nanostructure was constructed from a tyrosine-rich peptide (H-YYACAYY-OH) via mediating Pd2+ ions as well as changing temperature. This novel assembly technique provided a recyclable Pd nano-catalyst with a function of reversible thermal phase transition between the homogeneous and heterogeneous states for cross-coupling reactions.

Solid-Phase Synthesis of Peptide-Conjugated Perylene Diimide Bolaamphiphile and Its Application in Photodynamic Therapy

Here, we describe a rapid and efficient synthetic method of peptide-conjugated perylene diimide (P-PDI) using solid-phase peptide synthesis (SPPS). Due to severe insolubility of perylene dianhydride (PDA) as a starting material of perylene diimide (PDI), PDA was initially conjugated with amino acids to obtain soluble PDI derivatives. Target peptides were synthesized on a 2-chlorotrityl chloride resin using the SPPS method and then conjugated with the amino acid-appended PDI. Various conditions such as loading levels, reaction times and solvents were optimized for introducing the peptides to both sides of the amino acid-appended PDI. The final P-PDI was obtained with a maximum yield of 80% in 12 h. Its singlet oxygen-derived phototoxicity on cells was confirmed, which could be applicable to photodynamic therapy.