Benzophenone-Based ncAAs (e.g., BpA)
Genetic code expansion (GCE) technology has significantly advanced protein science by enabling the site-specific incorporation of non-canonical amino acids (ncAAs) into proteins. By engineering highly efficient, orthogonal aaRS/tRNA pairs, our platform facilitates the precise installation of photo-crosslinking ncAAs. This powerful methodology allows for the covalent capture of transient and weak biomolecular interactions within native cellular environments. Leveraging our proprietary, high-throughput GCEngine platform, we provide end-to-end services, from orthogonal pair identification to in vivo validation, to support robust proximity-dependent labeling and interactome studies.
Photo-crosslinking offers a precise method for investigating biomolecular interactions within live cells. The technique involves genetically encoding an ncAA bearing a photo-activatable crosslinker at a defined site within a "bait" protein. Under physiological conditions, this moiety remains inert. Upon exposure to specific wavelengths of UV light, it is rapidly converted to a highly reactive species (e.g., diradical, carbene, or nitrene) with a lifetime on the nanosecond to microsecond scale. This species can form a covalent bond with any proximal molecule (e.g., protein, nucleic acid, lipid) within a short radius. This covalent "snapshot" enables the subsequent isolation, identification, and characterization of interaction partners, transforming dynamic events into stable, analyzable complexes.
Fig.1 NcAAs for photocrosslinking. (Aydin, Y., and Coin, I., 2023)
The site-specific incorporation of photo-crosslinking ncAAs has become a cornerstone method for studying protein interactions in living systems. It provides unique insights into transient, weak, or spatially constrained interactions that are often inaccessible to conventional methods.
Elucidating Protein Interaction Networks
Captures weak, transient, or endogenous interactors (e.g., enzyme substrates, chaperone substrates), which are frequently missed in traditional pull-down assays.
Mapping Ligand-Receptor Interfaces
Serves as a proximity sensor to identify contact residues or bound molecules, providing structural information for protein-ligand complexes.
Studying Dynamic Interaction Kinetics
Enables time-resolved analysis of interaction dynamics, such as stimulus-induced association or dissociation events in live cells.
Trapping Enzymatic Intermediates
This approach traps fleeting enzyme-substrate complexes and reaction intermediates, providing mechanistic insights into catalysis and ATPase function.
Investigating Host-Pathogen Interactions
Mapping both intra-pathogen and pathogen-host protein-protein interactions by encoding photo-crosslinkers in pathogenic organisms.
Analyzing Membrane Protein Function
Probes the function and conformational states of integral membrane proteins (e.g., GPCRs, ion channels) in their native cellular context.
Built upon our proprietary GCEngine platform, we offer a comprehensive, collaborative service for photo-crosslinking ncAA incorporation. Our end-to-end solution includes strategic consultation, experimental design, molecular and cellular engineering, protein expression with ncAA incorporation, execution of controlled crosslinking experiments, and downstream analysis. This integrated approach streamlines the technical process, accelerating timelines from conceptual design to biologically meaningful data.
The selection of a photo-activatable moiety is critical, as it dictates the spatial resolution, crosslinking efficiency, and structural integrity of the protein under study. The choice among these moieties depends on the specific experimental goals, balancing factors such as crosslinking radius, reactivity lifetime, steric demand, and biocompatibility. Our platform supports the incorporation of a diverse array of photo-crosslinking ncAAs.
Benzophenone-Based ncAAs (e.g., BpA)
Benzophenones feature a diaryl ketone group that, upon UV irradiation at 350-365 nm, transitions into a reactive triplet diradical state.
Key Advantage: A distinguishing feature is the recyclability of the excited state; if the diradical does not find a proximal C-H bond to react with, it can relax back to the ground state. This allows for multiple excitation cycles, significantly enhancing crosslinking yields for stable protein-protein interactions. They are chemically inert toward water and exhibit a low propensity for non-specific background reactions, though their relatively bulky size may occasionally cause steric perturbation.
Diazirine-Based ncAAs (e.g., DiZPK)
Diazirines contain a compact three-membered heterocyclic ring. Upon exposure to ~360 nm light, they eliminate nitrogen gas to generate a highly reactive, short-lived carbene intermediate.
Key Advantage: Carbenes are among the most reactive species in chemistry, capable of universal insertion into both C-H and heteroatom-H bonds. This makes diazirines exceptionally versatile for capturing transient or "weak" interactions in diverse microenvironments. Due to their small molecular footprint (comparable to natural residues like Leucine or Isoleucine), they offer superior steric compatibility and are less likely to disrupt the native fold of the host protein.
Aryl Azide-Based ncAAs (e.g., Azi)
Aryl azides contain an azido group that undergoes photolysis under UV light to yield a nitrene intermediate, which can insert into C-H bonds or undergo rearrangement to form covalent adducts.
Key Advantage: The tunability of their activation wavelength and their distinct electronic properties make them valuable alternatives for targeting specific microenvironments (e.g., membrane interfaces) or when complementary crosslinking chemistry is required. Modern derivatives are optimized for activation at longer, more cell-friendly wavelengths, significantly reducing phototoxicity.
Our platform is uniquely equipped to design and implement customized strategies. From novel ncAA chemistry to specialized host system engineering, we collaborate closely with you to develop a precise and tailored solution that addresses the specific challenges of your target protein and biological question.
Custom ncAA & Orthogonal Pair Development
For novel experimental needs, we offer custom ncAA design and synthesis, coupled with high-throughput screening to evolve proprietary orthogonal aaRS/tRNA pairs with high activity and fidelity for your unique chemistry.
Host System Optimization
We provide tailored services across diverse expression systems (E. coli, yeast, mammalian cells), optimizing the GCE machinery and culture conditions to maximize incorporation efficiency and target protein functionality.
Integrated Analysis Packages
Beyond providing crosslinked samples, we offer comprehensive downstream analysis packages. This can include mass spectrometry, proteomic analysis, and structural biology support for characterization.
By combining deep expertise in synthetic biology and GCE with a robust GCEngine platform, our services are designed to de-risk and accelerate your protein interaction discovery and engineering projects. We are committed to delivering reliable, reproducible data that meets the rigorous demands of modern life science research. Contact us to discuss how our photo-crosslinking ncAA incorporation services can illuminate the critical interactions driving your research.
All our services are exclusively intended for preclinical research purposes. They are not intended for diagnostic, therapeutic, or patient management applications.
A specialized platform advancing genetic code expansion through orthogonal tRNA/aaRS technologies, enabling precise ncAA incorporation for biotherapeutic development, synthetic biology, and diagnostics.