Methylglyoxal analysis

In the ozonolysis of 2,5-dimethylpyrrole (IV), methylglyoxal and glyoxal are formed in addition to ammonia (83%), formic acid, and acetic acid. The yield of the dioximes is about 24% and of p-nitrophenylosazones, 29 to 33%. For the molecular ratio, methylglyoxal to glyoxal, values of about 5 to 7 are found by analysis of the mixture of oximes a value of 7 has been found by analysis of the mixture of p-nitrophenylosazones. The dioximes and the p-nitrophenylosazones of both dicarbonyl compounds have been isolated in a pure form and were identified by mixed melting points with authentic samples. 

Methylglyoxal (MG) is a highly reactive a-dicarbonyl formed endogenously in numerous enzymatic and nonenzymatic reactions. MG is very volatile and often coelutes with the solvent peak when the mixture is prepared for GC analysis. Hence, many papers focusing on environmental, clinical, or food studies have been published on its detection and quantification using chemical derivatization. After derivatization, the specificity of analyte, which carries a unique functional group. 

Identification of the diacid butyl esters was conducted by comparing the GC retention times with those of authentic standards. Mass spectra of the organic compounds were also obtained with a GC/MS (ThermoQuest, Trace MS) using a similar GC condition. Duphcate analyses of several filter samples showed that the analytical errors for major diacids were within 10%. Spiked experiments using authentic standards (oxalic, malonic, succinic and adipic acids) in quartz filter showed that recoveries were 77% for oxalic acid and better than 86% for other diacids. Recoveries of glyoxylic acid, pyruvic acid, and methylglyoxal were 88, 72, and 47, respectively (Kawamura and Yasui, in preparation). The procedural blanks showed that contamination levels of the diacids during the analysis were less than 5% of the sample. The data reported here are corrected for the procedural blanks, but not for recoveries. 

Colitis was induced by 2% DSS in the drinking water. Methylglyoxal-modified proteins were identified by immunoblot analysis using anti-argpyrimidine monoclonal antibody (A). Hsp25 and /3-actin were identified by immunoblot analysis using anti- Hsp25 antibody (B) and anti- fi-actin antibody (C), respectively. 

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