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Incomplete Fmoc deprotection in solid-phase synthesis of peptides
1Department of Chemical Physics, H. C. Orsted Institute, University of Copenhagen, Denmark.
International Journal of Peptide and Protein Research
|January 1, 1994
Summary
Ineffective N-alpha-deprotection during solid-phase peptide synthesis, specifically with the Fmoc strategy, hinders amino acid coupling. This study identifies beta-sheet formation as the cause, offering insights for optimizing peptide synthesis.
Area of Science:
- Organic Chemistry
- Biochemistry
- Materials Science
Background:
- Solid-phase peptide synthesis (SPPS) is crucial for creating peptides.
- The Fmoc (9-fluorenylmethoxycarbonyl) strategy is widely used in SPPS.
- Challenges in deprotection and coupling steps can impede synthesis efficiency.
Purpose of the Study:
- To investigate sequence-dependent ineffective N-alpha-deprotection during Fmoc-SPPS of homo-oligopeptides.
- To identify the underlying causes of difficult deprotection and subsequent coupling.
- To optimize deprotection conditions for improved peptide synthesis.
Main Methods:
- Fmoc-based solid-phase peptide synthesis of leucine and alanine homo-oligopeptides.
- Systematic variation of deprotection conditions: time, temperature, solvents, and chaotropes.
- Monitoring of coupling and deprotection using colorimetry, Fast Atom Bombardment Mass Spectrometry (FAB MS), and High-Performance Liquid Chromatography (HPLC).
Main Results:
- Observed sequence-dependent ineffective N-alpha-deprotection with piperidine.
- Incomplete deprotection correlated with slow or incomplete amino acid coupling.
- Identified beta-sheet formation as the common physicochemical origin for both difficult deprotection and coupling.
Conclusions:
- Beta-sheet formation in peptide chains is a significant impediment in Fmoc-SPPS.
- Optimization of deprotection conditions can mitigate synthesis challenges.
- Understanding the physical chemistry of peptide aggregation is key to improving SPPS efficiency.