α-Chromanoxyl radical formed by the interaction of α-tocopherol (vitamin E) with alkoxyl radical or DPPH was found by electron spin resonance spectroscopy to react with glutathione and vitamin C to regenerate α-tocopherol.

Hydrophobic peptides are generally difficult to detect using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) because the majority of MALDI matrixes are hydrophilic and therefore have a low affinity for hydrophobic peptides. Here, we report on a novel matrix additive, o-alkylated dihydroxybenzoic acid (ADHB), which is a 2,5-dihydroxybenzoic acid (DHB) derivative incorporating a hydrophobic alkyl chain on a hydroxyl group to improve its affinity for hydrophobic peptides, thereby improving MALDI-MS sensitivity. The addition of ADHB to the conventional matrix α-cyano-4-hydroxycinnamic acid (CHCA) improved the sensitivity of hydrophobic peptides 10- to 100-fold. The sequence coverage of phosphorylase b digest was increased using ADHB. MS imaging indicated that hydrophobic peptides were enriched in the rim of a matrix/analyte dried spot when ADHB was used. In conclusion, the addition of ADHB to the standard matrix led to improved sensitivity of hydrophobic peptides by MALDI-MS.

Sodium hypochlorite (NaOCl) induced decomposition of organic hydroperoxides gave strong chemiluminescence. Chemiluminescence intensity reached its maximum a few seconds after the addition of sodium hypochlorite and decreased to the background level in three min. Good linear relationships were observed between total chemiluminescence counts in three min and the amounts of hydroperoxides. This chemiluminescence method can be applied to the detection of low levels of lipid hydroperoxides.

No abstract

Mass spectrometry (MS) is a highly sensitive analytical technique that is o en coupled with liquid chromatography (LC). However, some bu ering salts used in LC (e.g., phosphate and tris(hydroxymethyl) aminomethane (Tris)) are incompatible with MS since they cause ion-source contamination and signal suppression. In this study, we examined salt tolerance of MALDI and applied a matrix additive methylenediphosphonic acid (MDPNA) to reduce salt-induced signal suppression. MDPNA signi cantly improved the salt tolerance of MALDI-MS. Using ammonium formate bu er at pH 5.0, the e ective range of bu ering salt concentration in MALDI-MS using MDPNA was estimated up to 250 mM. MDPNA reduced signal suppression caused by bu ering salts at pH 4.0 to 8.0. We observed that MDPNA e ectively worked over a wide range of bu er conditions. MDPNA was further applied to hydrophilic interaction chromatography (HILIC) and chromatofocusing-MALDI-MS. As a result, the analytes in the eluent containing high-concentration salts were detected with high sensitivity. us, our study provides simple and fast LC-MALDI-MS analysis technique not having strict limitation of bu ering condition in LC by using matrix additive MDPNA.