Merck Millipore Direct Detect spectrometer

With Merck Millipore’s Direct Detect spectrometer, the user is simply required to spot 2 μL of the sample, blank with buffer and read. There is no sample prep, no tedious standard curves and no messy cuvettes or liquid waste.

The system exploits membrane technology that makes aqueous biological samples compatible with direct infrared (IR) analysis. IR spectroscopy exploits the fact that molecules absorb radiation at specific frequencies characteristic of their internal structure and functional groups.

A protein’s primary structure is formed by a long chain of amide bonds that show characteristic absorption in multiple regions of the IR spectrum, including the Amide I band at 1600-1690 cm^-1. By measuring the intensity of this Amide I band, the system accurately quantifies an intrinsic component of every protein without relying on amino acid composition, dye-binding properties or reduction-oxidation (redox) potential. In addition, amide bond quantitation is not subject to interference from many common buffer components, such as detergents, reducing agents, thiols and chelators, which are often problematic using traditional methods.

Like proteins, lipids also show characteristic absorption in the IR spectrum including the C-H symmetric stretching band at 2870-2840 cm^-1. The spatial separation of this C-H symmetric stretching band from the Amide I band enables users of the product to simultaneously analyse both protein and lipid content from the same spotted 2 μL sample.