Fmoc-Compatible and C-terminal-Sequence-Independent Peptide Alkyl Thioester Formation Using Cysteinylprolyl Imide.

We report an Fmoc-compatible and external-thiol-free method of peptide C-terminus thioesterification with cysteinylprolyl imide. The newly synthesized structure, i.e.

Cysteinylprolyl imide (CPI) peptide: a highly reactive and easily accessible crypto-thioester for chemical protein synthesis.

Native chemical ligation (NCL) between the C-terminal peptide thioester and the N-terminal cysteinyl-peptide revolutionized the field of chemical protein synthesis. The difficulty of direct synthesis of the peptide thioester in the Fmoc method has prompted the development of crypto-thioesters that can be efficiently converted into thioesters. Cysteinylprolyl ester (CPE), which is an - acyl shift-driven crypto-thioester that relies on an intramolecular - acyl shift to displace the amide-thioester equilibrium, enabled -thioesterification and subsequent NCL in one pot.

Simultaneous and Traceless Ligation of Peptide Fragments on DNA Scaffold.

Peptide ligation is an indispensable step in the chemical synthesis of target peptides and proteins that are difficult to synthesize at once by a solid-phase synthesis. The ligation reaction is generally conducted with two peptide fragments at a high aqueous concentration to increase the reaction rate; however, this often causes unpredictable aggregation and precipitation of starting or resulting peptides due to their hydrophobicities. Here, we have developed a novel peptide ligation strategy harnessing the two intrinsic characteristics of oligodeoxynucleotides (ODNs), i.

Hybridization-sensitive fluorescent oligonucleotide probe conjugated with a bulky module for compartment-specific mRNA monitoring in a living cell.

Live-cell RNA imaging at specific intracellular locations is technically limited because of the diffusive nature of small oligonucleotide probes. The bulky fluorescent light-up probes that possess streptavidin or gold nanoparticles at the end of oligonucleotides were designed and synthesized. The bulky probes allowed nucleus- and cytoplasm-selective monitoring of endogenous mRNAs through nuclear and cytoplasmic microinjection, respectively.