Nitric acid concentrated acid and nitric oxide for dilute acid. or Concentrated nitric acid oxidizes I, P, and S into HIO, HPO, and HSO, respectively. Nitric acid reacts with proteins to form yellow nitrated products. This reaction is known as the xanthoproteic reaction. This test is carried out by adding concentrated nitric acid to the substance being tested, and then heating the mixture. If proteins that contain amino acids with aromatic rings are present, the mixture turns yellow. Upon adding a base such as ammonia, the color turns orange. These color changes are caused by nitrated aromatic rings in the protein. Xanthoproteic
Methylmalonic acid Methylmalonic acid Methylmalonic acid (MMA) (conjugate base methylmalonate) is a dicarboxylic acid that is a "C"-methylated derivative of malonate. The coenzyme A linked form of methylmalonic acid, methylmalonyl-CoA, is converted into succinyl-CoA by methylmalonyl-CoA mutase, in a reaction that requires vitamin B as a cofactor. In this way, it enters the Krebs cycle, and is thus part of one of the anaplerotic reactions. Increased methylmalonic acid levels may indicate a vitamin B deficiency. However, it is sensitive (those with the disease almost always test positive) but not specific (those that do not have the disease do not always test negative).