Image: Direct Detect Protein Quantitation System (Photo Courtesy of EMD Millipore).
A system for rapid, simplified protein quantitation has been introduced that enables infrared-based measurement of amide bonds in protein chains.
The system does not rely on amino acid composition, dye-binding properties, or redox potential unlike conventional assays based on ultraviolet- visual (UV-Vis) spectroscopy, which do rely on absorbance by a protein’s aromatic amino acids and therefore have limited utility.
The Direct Detect system employs a hydrophilic polytetrafluoroethylene (PTFE) membrane designed to be transparent in most of the infrared spectral region and enables application of biomolecular 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, an accurate standard for quantitation, yet can be time-consuming and often costly.
The system relies on infrared-based detection of biomolecules, so that the users can obtain accurate and reproducible protein quantitation in the presence of reducing agents and detergents. As a result, the Direct Detect (EMD Millipore, Billerica, MA, USA) 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.
John Sweeney, Head of Life Science Business Field, EMD Millipore, said, "In addition to its analytical powers, the Direct Detect system provides a groundbreaking departure from traditional sample preparation requirements typical of biomolecular quantitation. After samples are spotted on assay cards, they can be stored in ambient conditions without appreciable change in readout. Another important advantage over conventional assays is that the Direct Detect calibration standard curve requires generation once, which provides additional time savings and ease of use." EMD Millipore is a division of Merck (Darmstadt, Germany).