The Direct Detect system for protein quantitation from EMD Millipore uses membrane technology to enable infrared-based measurement of amide bonds in protein chains without relying on amino acid composition, dye-binding properties, or redox potential. Conventional assays based on UV-Vis spectroscopy rely on absorbance by a protein’s aromatic amino acids.
 
Samples are spotted on assay cards, which can be stored in ambient conditions without appreciable change in readout. The calibration standard curve requires generation once, which provides additional time savings and ease of use.
 
The system employs a hydrophilic polytetrafluoroethylene (PTFE) membrane designed to be transparent in most of the infrared spectral region and enables application of biomolecule solutions directly onto the membrane. The system delivers more universally applicable and faster protein quantitation, requiring minimal sample consumption. System accuracy and precision are comparable with results obtained by amino acid analysis, the company reports. 
 
Because the system relies on IR-based detection of biomolecules, users can obtain accurate and reproduc¬ible protein quantitation in presence of reducing agents and detergents.  The system can measure protein concentrations from 0.2 mg/mL to 5 mg/mL within seconds, without any bio- or immunochemical staining, directly from samples, including buffered solutions.
 components, such as lipids and nucleic acids.
 
EMD Millipore