A simple protocol for combinatorial cyclic depsipeptide libraries sequencing by matrix-assisted laser...

Area of Science:

• Biochemistry
• Organic Chemistry
• Analytical Chemistry

Background:

• Cyclic peptides are valuable in therapeutics and diagnostics.
• Screening peptide libraries with mass spectrometry (MS) aids in identifying target-binding peptides.
• Analyzing cyclic peptide mass spectra is challenging due to complex fragmentation.

Purpose of the Study:

• To develop a simple protocol for synthesizing combinatorial cyclic peptide libraries.
• To enable efficient ring-opening and sequencing of cyclic peptides using MS.
• To facilitate the discovery of cyclic peptides for various applications.

Main Methods:

• Utilized a 4-hydroxymethylbenzoic acid linker for benzyl ester formation.
• Incorporated a glycolamidic ester group using glycolic acid.
• Developed a multi-step synthesis including Fmoc-Asp[2-phenylisopropyl (OPp)]-OH incorporation, library synthesis, cyclization, and deprotection.
• Employed ammonia for simultaneous ring-opening and peptide release.
• Analyzed peptides using matrix-assisted laser desorption/ionisation MS.

Main Results:

• Successfully synthesized one-bead-one-cyclic depsipeptide libraries.
• Demonstrated efficient simultaneous ring-opening and peptide release.
• Enabled peptide sequence determination from tandem MS data.
• The protocol is accessible to labs without specialized organic synthesis expertise.

Conclusions:

• The proposed method simplifies the preparation and analysis of cyclic peptide libraries.
• This approach facilitates the identification and sequencing of cyclic peptides for therapeutic and diagnostic applications.
• The protocol's ease of use makes it broadly applicable in research settings.