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Assay Services

Colorful infographic depicting customized protein assay services, baculovirus titer assay, thermal shift analysis (TSA), insect mass analysis services from Proteos | US-based recombinant protein production CRO

Assay Services

Baculovirus titer assay, thermal shift assay (TSA), intact mass measurement, colorimetric and fluorometric assays.

Our available assay services include baculovirus titer assay, thermal shift assay (TSA), intact mass analysis, commercially available colorimetric and fluorometric assays. These services can be used for stand-alone analysis or integrated into a customized gene-to-protein workflow to meet your specific needs. 

 

Baculovirus Titer Assay 

We utilize a plate-based flow cytometry assay for rapid, reproducible titer determination (infectious particles per mL) of baculovirus stocks, enabling infection of insect cells using a calculated MOI (multiplicity of infection). Understanding MOI is an important step in consistent production of recombinant proteins using baculovirus mediated expression platforms. 

Advantages: 

  • Accurate determination of baculovirus titers in the range of 107-109 IU/mL. 
  • Requires as little as 1 mL of baculovirus stock for the assay to be performed in triplicate 
  • Results in as few as 3-5 business days from sample receipt 

 

Thermal Shift Assay (TSA) 

Thermal shift assay (TSA), also known as Differential Scanning Fluorimetry (DSF), is widely used in structural biology and drug discovery to study the thermal stability and binding properties of proteins, aiding in the characterization and optimization of protein-based research. 

Applications: 

  • Determination of protein stability 
  • Evaluation of ligand binding 
  • Comparative studies of protein variants or mutants 
  • Optimization of protein formulation  
  • Analysis of protein-protein interactions 

Intact Mass Analysis 

Mass spectrometry is a powerful tool for protein characterization. Our intact mass analysis service offers high-accuracy molecular weight determination for confirming the integrity of protein sequences and the identification of post-translational modifications or chemical adducts. 

Common PTM and adducts detectable by intact mass: 

  • Phosphorylation/dephosphorylation 
  • Acetylation 
  • Glycosylation 
  • Disulfide bond formation 
  • Removal of initiator Met 
  • β-ME and glutathione adducts 
  • Biotinylation 

Frequently Asked Questions

What instrumentation do you use for intact mass analysis?

We utilize the Waters BioAccord LC-MS, an electrospray ionization-time of flight (ESI-TOF) mass spectrometer for intact mass determination of proteins and antibodies. The instrument is self-optimizing to ensure consistent, high-quality data. 

How does the thermal shift assay work?

The thermal shift assay relies on the principle that as proteins undergo thermal denaturation, their hydrophobic regions become exposed. These exposed regions can then interact with hydrophobic dyes or fluorescent probes. By tracking changes in fluorescence intensity, the protein’s melting temperature (Tm), an indicator of its stability, can be determined. 

What is MOI and why is it important?

MOI (multiplicity of infection) measures the number of infectious virus particles used for infection relative to the number of insect cells in the culture. Infections based on MOI, rather than volume to volume, result in greater consistency between pilot and production scale expression and batch-to-batch production because the titer of a baculovirus stock will decrease over time.

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