NOS Colorimetric Non-Enzymatic Assay


The NOS Colorimetric Non-Enzymatic Assay is for the quantitative determination of Nitric Oxide Synthase in biological fluids by a microplate assay.

SKU: NOS39-K01 Categories: , ,

NOS Colorimetric Non-Enzymatic Assay

The NOS Colorimetric Non-Enzymatic Assay is For Research Use Only

Size: 1 x 96 wells
Sensitivity: 1 pmol/µL or ~0.5 µM
Dynamic Range: 0.5 – 100 µM
Incubation Time: 5 minutes
Sample Type: Biological Fluids
Sample Size: 5 µl
Alternative Name: Nitric Oxide Synthase

Assay Background

This Nitric Oxide Synthase Colorimetric Non-enzymatic Assay allows you to measure total nitric oxide (NO) produced for in vitro experimental systems following conversion of nitrate to nitrite by metallic cadmium.  Nitric oxide can be spectrophotometrically assayed by measuring the accumulation of its stable degradation products, nitrate and nitrite.  The ratio of these two products in biological fluids, tissue culture media, etc. may vary substantially.  Hence, for accurate assessment of the total nitric oxide generated, one must monitor both nitrate and nitrite.  An excellent solution to this problem involves the conversion of nitrate to nitrite catalyzed by cadmium. This is then followed by the quantitation of nitrite using the griess reaction.

This kit is suitable for the quantitative determination of total nitric oxide in samples that have high protein concentrations. The cadmium catalyst proves far more robust when in the presence of harsh deproteinating reagents than the alternative, nitrate reductase.

Related Products

Nitric Oxide Synthase Colorimetric Non-Enzymatic Assay (Refill Kit)
NOS Ultrasensitive Colorimetric Assay
Nitric Oxide Synthase Colorimetric Assay Kit

Additional Information

Assay Principle

In aqueous solution, nitric oxide rapidly degrades to nitrate and nitrite. Spectrophotometric quantitation of nitrite using Griess Reagent is straightforward, but does not measure nitrate. This kit employs metallic cadmium for quantitative conversion of nitrate to nitrite prior to quantitation of nitrate using Griess reagent — thus providing for accurate determination of total NO production.

Assay Procedure

  1. Establish a plate layout  accounting for each sample and standard.
  2. Add 100 mL of sample and standard to their respective wells on the plate.  Note: samples may require further dilution with DD water if the concentration exceeds the standard curve parameters.
  3. Add 50mL Color Reagent #1 and shake briefly.
  4. Add 50mL Color Reagent #2.  Shake for 5 minutes at room temperature.
  5. Read plate at 540 nm and proceed to the calculations section.


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