The IDK® Tryptophan ELISA is intended for the quantitative determination of L-tryptophan in human EDTA plasma, serum, and dried blood spots.

For research use only. Not for use in diagnostic procedures.

For Laboratory Professional Use Only.

This is the RUO version of Immundiagnostik part number K 7730.

Test Principle of the IDK® Tryptophan ELISA

The IDK® Tryptophan ELISA is designed for the quantitative determination of L-tryptophan. The assay is based on the method of competitive enzyme-linked immunoassays.

The sample preparation includes the addition of a derivatization reagent for tryptophan derivatization. Afterward, the treated samples and a polyclonal L-tryptophan antiserum are incubated in the wells of a microtiter plate coated with L-tryptophan derivative (tracer). During the incubation period, the target L-tryptophan in the sample competes with the tracer, immobilized on the wall of the microtiter wells, to bind the polyclonal antibodies.

During the second incubation step, a peroxidase-conjugated antibody is added to each microtiter well to detect the L-tryptophan antibodies. After washing away the unbound components, tetramethylbenzidine (TMB) is added as a peroxidase substrate.

Finally, the enzymatic reaction is terminated by an acidic stop solution. The color changes from blue to yellow, and the absorbance is measured in the photometer at 450 nm. The intensity of the yellow color is inversely proportional to the L-tryptophan concentration in the sample; this means high L-tryptophan concentration in the sample reduces the concentration of tracer-bound antibodies and lowers the photometric signal.

A dose-response curve of absorbance unit (optical density, OD at 450 nm) vs. concentration is generated using the values obtained from the standard. The presence of L-tryptophan in the samples is determined directly from this curve.