Cell-Penetrating Peptides Containing Fluorescent d-Cysteines.

Area of Science:

• Organic Chemistry
• Biochemistry
• Biophysics

Background:

• Development of novel fluorescent amino acids is crucial for biological imaging.
• Non-natural amino acids offer unique properties for peptide modification.
• Solid-phase peptide synthesis (SPPS) is a standard technique for peptide construction.

Purpose of the Study:

• To synthesize and characterize a series of fluorescent d-cysteine (Cys) derivatives.
• To evaluate the utility of these novel amino acids in cell-penetrating peptides (CPPs).
• To monitor the cellular internalization of fluorescently labeled CPPs using fluorescence microscopy.

Main Methods:

• Diastereoselective 1,4-conjugate addition of aryl thiols to a chiral bicyclic dehydroalanine.
• Transformation of Michael adducts into d-cysteine derivatives and N-Fmoc-d-cysteine for SPPS.
• Incorporation of coumaryl and dansyl Cys derivatives into CPP sequences via SPPS.
• Optical property analysis and fluorescence microscopy of labeled peptides in cell lines.

Main Results:

• Successful synthesis of fluorescent d-cysteine derivatives with high chemo- and stereoselectivity.
• Demonstrated utility in standard SPPS for creating modified peptides.
• Incorporated fluorescent peptides showed distinct optical properties in various cell lines.
• Confirmed cellular internalization of fluorescent peptides by microscopy.

Conclusions:

• A novel and efficient synthetic route to fluorescent d-cysteine amino acids was established.
• These non-natural amino acids are valuable tools for creating fluorescently labeled peptides for biological studies.
• The fluorescent peptides effectively track cellular uptake and localization, advancing peptide-based imaging techniques.