At our company, we specialize in identifying the direct protein targets of natural products through our bioactive natural products target identification technology platforms. Photoaffinity labeling (PAL) has emerged as an indispensable tool in our platform. By utilizing light-controllable reactivity, PAL allows researchers to convert weak, reversible binding events into permanent covalent bonds. This enables the "capture" of target proteins even within the crowded environment of a live cell or complex lysate, providing a clear map of the molecular interactions driving biological activity.
What is PAL?
PAL is a technique that employs a bifunctional small-molecule probe—a synthetic analog of your bioactive natural product. This probe is equipped with a photoreactive group (photophore) that remains inert under normal conditions but becomes highly reactive when exposed to specific wavelengths of light (usually UV). When the probe binds to its target protein, brief irradiation triggers the photophore to form a covalent cross-link with the amino acid residues in the immediate vicinity of the binding pocket. This "stamps" the protein, allowing it to be isolated and identified through downstream proteomics.
Fig. 1. Representative PAL probes [1].
Our PAL-Based Technology Platform
Our company has established a comprehensive and modular PAL-based technology platform specifically optimized for bioactive natural products. The platform integrates chemistry, biology, and proteomics to deliver end-to-end target identification solutions.
Key Components of Our Platform
- Rational probe design guided by SAR and structural analysis
- Optimized photo-crosslinking protocols for different biological systems
- High-efficiency click chemistry and affinity enrichment workflows
- Quantitative proteomics and bioinformatics analysis
- Validation strategies including competition assays and functional studies
Our PAL Probe Design Capabilities
The success of PAL depends entirely on the quality of the probe. A poorly designed probe may lose its biological activity or label proteins non-specifically. Our chemical biology team excels in bifunctional and trifunctional probe design:
- The Recognition Element: We use SAR (Structure-Activity Relationship) data to identify "bolt-on" positions that do not interfere with binding.
- The Photoreactive Group (Photophore): We offer a selection of photophores tailored to the specific project, including benzophenone, azide, tetrazole, diazirine, α-Ketoamide, isoxazole, and cyclobutane diazirine.
- The Reporter Tag (The "Handle"): We primarily utilize Click Chemistry (Alkyne/Azide) handles. By using a small alkyne tag on the probe, we can "click" on biotin for enrichment or fluorescent dyes for visualization after the labeling event has occurred. This minimizes the size of the probe and improves cell permeability.
Key strengths include:
- Minimal Structural Perturbation: Strategic placement of photo-reactive groups to preserve activity
- Multiple Photo-Crosslinker Options: Diazirines for short-range labeling, benzophenones for flexible interactions
- Flexible Reporter Strategies: Alkyne/azide handles compatible with click chemistry
- SAR-guided Optimization: Iterative refinement based on biological activity testing
- Scalability: Synthesis of probes suitable for cellular and proteomic studies
Key Advantages of PAL
- Direct Target Capture: Covalent crosslinking ensures direct identification of binding proteins rather than downstream effects.
- Physiological Relevance: Experiments can be performed in live cells, preserving native protein conformations and interactions.
- High Sensitivity: Capable of detecting low-abundance proteins and weak or transient interactions.
- Broad Applicability: Suitable for enzymes, receptors, scaffolding proteins, and membrane proteins.
- Unbiased Discovery: Enables proteome-wide target profiling without prior assumptions.
- Compatibility with Natural Products: Especially powerful for complex, non-synthetic molecules with unknown mechanisms.
PAL is a powerful and versatile technology for unraveling the molecular targets of bioactive natural products. Through our advanced PAL technology, robust probe design capabilities, and integrated proteomics workflows, we provide a reliable solution for target identification and mechanism-of-action studies.
Online Inquiry
Frequently Asked Questions (FAQ)
Q1: Is probe synthesis always required?
Q2: Can PAL be used in live cells?
A: Yes. Our platform supports PAL experiments in live cells, allowing target identification under physiologically relevant conditions.
Q3: How are false positives controlled?
A: We employ competition assays with the parent compound, negative controls, and orthogonal validation methods to ensure target specificity.
Reference
- Zhou Y. F., et al. Targeting the Reactive Proteome: Recent Advances in Activity-Based Protein Profiling and Probe Design[J]. Biomolecules, 2025, 15(12): 1699.