Kinetically Tunable Photostability of Fluorogen-Activating Peptide-Fluorogen Complexes

Area of Science:

• Biochemistry
• Molecular Biology
• Chemical Biology

Background:

• Fluorophores are crucial for biological detection, with high photostability, labeling specificity, and genetic encoding being key desired qualities.
• Fluorogen-activating peptides (FAPs) bind fluorogens noncovalently, offering potential for enhanced photostability and fluorogenic labeling.
• Understanding FAP-fluorogen interactions is essential for developing advanced biological imaging tools.

Purpose of the Study:

• To compare the photostabilities of malachite green (MG)-binding and thiazole-orange-binding FAPs.
• To elucidate the distinct mechanisms of photostability related to FAP-fluorogen complex dissociation rates.
• To develop novel FAPs with improved photostability for biological labeling applications.

Main Methods:

• Comparative analysis of FAP photostability under limiting and excess fluorogen conditions.
• Investigation of FAP-fluorogen complex dissociation rates and their correlation with photostability.
• Utilizing selection pressure based on bleaching, flow cytometry, and site-specific mutagenesis to engineer FAPs.

Main Results:

• FAPs with slow dissociation exhibited dye encapsulation and single-step bleaching, suggesting protection from degradation.
• FAPs with rapid dissociation demonstrated repeated cycles of binding and photostability through fluorogen exchange.
• A modified FAP with enhanced photostability was developed, characterized by rapid dissociation of the malachite green fluorogen.

Conclusions:

• Noncovalent association mechanisms significantly influence photostable labeling in biological systems.
• FAPs with rapid dissociation enable intermittent labeling and enhanced photostability via fluorogen exchange.
• Novel FAP reagents were developed for robust and versatile photostable labeling of biological targets.