Urea is classified on the basis of its biuret content.

A further effort to prepare a colorless biuret reagent.

The test is so named because it also gives a positive reaction to the peptide-like bonds in the biuret molecule.

The most common impurity of synthetic urea is biuret, which impairs plant growth.

The biuret content is a serious concern because it is often toxic to the very plants that are to be fertilized.

Typical impurities in the production are biuret and isocyanic acid:

Franz Hofmeister made the proposal in the morning, based on his observations of the biuret reaction in proteins.

It is based on the biuret reagent, a blue solution that turns violet upon contact with proteins, or any substance with peptide bonds.

Not all biuret tests require the biuret reagent.

This is achieved by the chelation of bicinchoninic acid with the cuprous ion formed by the biuret reaction.

NPN are given to ruminants in the form of pelleted urea, ammonium phosphate and/or biuret.

Hofmeister also argued for peptide bonds based on the biuret reaction observed with all proteins but never with free amino acids.

The traditional method for measuring total protein uses the biuret reagent, but other chemical methods such as Kjeldahl method, dye-binding and refractometry are now available.

The term "biuret" also describes a family of organic compounds with the functional group -(HN-CO-)N-.

The test and reagent do not actually contain biuret; they are so named because both biuret and proteins have the same response to the test.

Ammeline can be synthesized by the pyrolysis of urea, or the condensation reaction among 2 moles of dicyandiamide with 1 mole of biuret.

Thus, the two substrates of this enzyme are cyanuric acid and HO, whereas its two products are biuret and CO.

He received a PhD in 1957 for his work on the structure of biuret hydrate, where he completed most of the calculations for the crystal structure by hand.

Since biuret has the formula NH-CO-NH-CO-NH, that suggested the presence of similar peptide bonds in proteins.

For example, Archer Daniels Midland manufactures an NPN supplement for cattle, which contains biuret, triuret, cyanuric acid and urea.

Thus dimethyl biuret is CHHN-CO-NR'-CO-NHCH.

Millon's test is not specific for proteins (it actually detects phenolic compounds), and so must be confirmed by other tests for proteins such as the biuret test and the ninhydrin reaction.

Intermediates and impurities include biuret, cyanuric acid, and potassium allophanate (KOCNHC(O)NH), as well as unreacted starting urea, but these species are unstable at 400 C.

The reagent is commonly used in a biuret protein assay, a colorimetric assay used to determine protein concentration-such as UV-VIS at wavelength 540 nm (to detect the Cu ion).

His research group extended its interests beyond purely organic compounds and on to metal complexes (such as copper biuret, one of the first bioinorganic substances to be structurally determined) and went on to determine the structures of numerous metal complexes of amino acids and peptides.