Search results for "Xanthoproteic reaction"
showing 2 items of 2 documents
Protein Tyrosine Nitration Induced by Heme/Hydrogen Peroxide: Inhibitory Effect of Hydroxycinnamoyl Conjugates
2006
The present study was designed to optimize the experimental conditions that govern the heme-catalyzed nitration of protein tyrosine residues by nitrite, and, within this framework, to study the effects of 3,5-dicaffeoylquinic acid and its methyl ester, both of which have been previously reported to be antioxidants and inhibitors of leukocyte functions. Although the presence of hydrogen peroxide is essential in cell-free systems, an excess of this compound was found to be detrimental, so much so that an increase in hemin concentration actually resulted in an inverse effect on the reaction, depending on the levels of fixed hydrogen peroxide. Unlike previous reports on nitrite-induced albumin …
Determination of the protein and free amino acid content in a sample using o-phthalaldehyde and N-acetyl-L-cysteine
1990
A spectrophotometric method is proposed for determining the protein content in a sample after total acid hydrolysis. In the procedure, free amino acids are caused to react with o-phthalaldehyde and N-acetyl-L-cysteine at pH 9.5, using isoleucine as the reference compound. Correction factors are used to take into account the differences between the molar absorptivities of the amino acid isoindoles and the recoveries of the amino acids after the hydrolysis treatment. The limit of detection was in the range 40-50 micrograms of protein, and the recoveries were usually 101 +/- 3% with a coefficient of variation lower than 4%. The free amino acid content in a partially hydrolysed protein was also…