The chromogenic substrate MAOS reagent is a high-sensitivity chromogenic reagent commonly used in biochemical kits. The full name is N-Ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethylaniline sodium Salt monohydrate; TMB is also a commonly used color reagent. The color development principles of the two are similar, but there are some differences.
Trinder Reagent MAOS
MAOS: The reagent belongs to a new type of Trinder's reagent. In the presence of hydrogen peroxide and peroxidase POD, it forms a very stable orange or red quinone with 4-aminoantipyrine (4-AAP). It can be oxidatively coupled with 3-methylbenzothiazole sulfone hydrazone (MBTH) to form a very stable purple or blue dye. The molar absorbance of MBTH coupled dye is 1.5-2 times higher than that of 4-AA coupled dye; however, 4-AAP solution is more stable than MBTH solution, so Trinder's reagent is more used with 4-AAP.
TMB reagent: It is a chromogenic substrate used in ELISA kits. TMB or TMBZ under the catalysis of peroxidase is blue after being oxidized by hydrogen peroxide, and turns yellow after adding stop solution. The OD value was measured with a microplate reader at a wavelength of 450 nm, and the antigen concentration was proportional to the OD value, and the concentration of antigen in the sample was calculated by drawing a standard curve. It does not need to be like chromogens ADPS, TOOS, MAOS, etc. It needs to add another compound (such as 4-AA, MBTH) to react to show color, but TMBZ needs to react under acidic conditions (HCl) for color reaction. Some biochemical tests are more accurate under neutral conditions. The catalytic performance of some enzymes is very sensitive to pH, and it is necessary to maintain a neutral environment to maintain activity, which limits the application of TMB.
Like other Trinder reagents, MAOS is a highly water-soluble sodium salt of aniline. When coupled with 4-aap, the N of aniline becomes a C=N double bond, and the para position is combined with the amino group of 4-AA to form a C=N double The bond, thus forming a quinoneimine structure, is similar to the C=O double bond of p-benzoquinone, and the absorption wavelengths are in the visible light region, resulting in a color reaction. The maximum absorption wavelength of the oxidized product of MAOS is far more than that of ordinary color reagents, and its product UV absorption wavelength is quite high at 630nm. If you use a product like MAOS, the maximum absorption wavelength of the product is in the ultraviolet region and is relatively high, which can greatly reduce the interference of substances with similar absorption wavelengths in the sample. Therefore, it is recommended to use MAOS as the color development substrate for some biochemical detection items that require highly accurate values.
All in all, the difference between MAOS and TMB is that the absorption wavelength of the color product is much higher than that of TMB. The coupling requires the introduction of 4-AAP or MBTH, which can be detected in a neutral pH environment. Desheng currently produces 9 new Trinder’s reagents including MAOS.
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