A Highly Efficient Method for Site-Specific Modification of Unprotected Peptides after Chemical Synthesis

Synthesis of an amphiphilic copolymer using biopolymer-dextran via combination of ROP and RAFT techniques

The ring-opening polymerization (ROP) and reversible addition−fragmentation chain-transfer polymerization (RAFT) are efficient synthetic approaches to develop self-assembled copolymers with narrow dispersity (Ɖ). The aim of this work is to develop...

N-Sulfanylethylaminooxybutyramide (SEAoxy): A Crypto-Thioester Compatible with Fmoc Solid-Phase Peptide Synthesis

An N-sulfanylethylaminooxybutyramide (SEAoxy) has been developed as a novel thioester equivalent for native chemical ligation. SEAoxy peptide was straightforwardly synthesized by conventional Fmoc solid-phase peptide synthesis without a problem. Moreover, SEAoxy peptide could be directly applied to native chemical ligation owing to the intramolecular N-to-S acyl shift that releases the peptide-thioester in situ. This methodology was successfully applied to the synthesis of two bioactive peptides.

Peptide purification using the chemoselective reaction between N-(methoxy)glycine and isothiocyanato-functionalized resin

An efficient peptide purification strategy is established, comprising the selective reaction of an N-terminal N-(methoxy)glycine residue of the peptide and isothiocyanato-functionalized resins, and subsequent Edman degradation. These reactions take place in acidic media; in particular, the Edman degradation proceeds smoothly in media containing more than 50% trifluoroacetic acid (v/v). These acidic conditions offer increased solubility, making them advantageous for the purification of hydrophobic and aggregation-prone peptides. The effectiveness of this method, together with scope and limitations, is demonstrated using model peptides and the practical purification of the loop region of the human dopamine D2 receptor long isoform (residues 240-272). Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

Site-specific labeling of synthetic peptide using the chemoselective reaction between N-methoxyamino acid and isothiocyanate

Site-specific labeling of synthetic peptides carrying N-methoxyglycine (MeOGly) by isothiocyanate is demonstrated. A nonapeptide having MeOGly at its N-terminus was synthesized by the solid-phase method and reacted with phenylisothiocyanate under various conditions. In acidic solution, the reaction specifically gave a peptide having phenylthiourea structure at its N-terminus, leaving side chain amino group intact. The synthetic human β-defensin-2 carrying MeOGly at its N-terminus or the side chain amino group of Lys(10) reacted with phenylisothiocyanate or fluorescein isothiocyanate also at the N-methoxyamino group under the same conditions, demonstrating that this method is generally useful for the site-specific labeling of linear synthetic peptides as well as disulfide-containing peptides.

2-(N-Fmoc)-3-(N-Boc-N-methoxy)-diaminopropanoic acid, an amino acid for the synthesis of mimics of O-linked glycopeptides

Amino acids with N-alkylaminooxy side chains have proven effective for the rapid synthesis of neoglycopeptides. Chemoselective reaction of reducing sugars with peptides containing these amino acids provides glycoconjugates that are structurally similar to their natural counterparts. 2-(N-Fmoc)-3-(N-Boc-N-methoxy)-diaminopropanoic acid (Fmoc: 9-fluorenylmethoxycarbonyl; Boc: t-butyloxycarbonyl) was synthesized from Boc-Ser-OH in >40% overall yield and incorporated into peptides by standard Fmoc chemistry based solid phase peptide synthesis. The resulting peptides are efficiently glycosylated and serve as mimics of O-linked glycopeptides. The synthesis of this derivative greatly expands the availability of the N-alkylaminooxy strategy for neoglycopeptides.

Synthesis and biological activities of aryl-ether-, biaryl-, and fluorene-aspartic acid and diaminopropionic acid analogs as potent inhibitors of the high-affinity glutamate transporter EAAT-2

Excitatory amino acid transporters (EAATs) play a pivotal role in maintaining glutamate homeostasis in the mammalian central nervous system, with the EAAT-2 subtype thought to be responsible for the bulk of the glutamate uptake in forebrain regions. A complete elucidation of the functional role of EAAT-2 has been hampered by the lack of potent and selective pharmacological tools. In this study, we describe the synthesis and biological activities of novel aryl-ether, biaryl-, and fluorene-aspartic acid and diaminopropionic acid analogs as potent inhibitors of EAAT-2. Compound (16) represents one of the most potent (IC50=85+/-5 nM) and selective inhibitors of EAAT-2 identified to date.

Watching proteins in the wild: fluorescence methods to study protein dynamics in living cells

The advent of GFP imaging has led to a revolution in the study of live cell protein dynamics. Ease of access to fluorescently tagged proteins has led to their widespread application and demonstrated the power of studying protein dynamics in living cells. This has spurred development of next generation approaches enabling not only the visualization of protein movements, but correlation of a protein's dynamics with its changing structural state or ligand binding. Such methods make use of fluorescence resonance energy transfer and dyes that report changes in their environment, and take advantage of new chemistries for site-specific protein labeling.