A method for detection of 4-hydroxy-2-nonenal adducts in proteins

We developed a procedure to measure 4-hydroxy-2-nonenal (HNE)-amino acid adducts using the fluorescent probe 2-aminopyridine (2-AP). The method is based on the fact that HNE forms Michael addition-type amino acid adducts possessing an aldehyde functionality, which upon reaction with 2-AP in the presence of NaBH3CN can be converted to their pyridylaminated derivatives. The HNE-amino acid adducts, namely Michael addition-type HNE-cysteine, HNE-histidine, and HNE-lysine adducts, after pyridylamination were resistant to conventional acid-hydrolysis conditions for protein (6 N HCl/110 degrees C/24 h) and could be detected by HPLC with a fluorescence detector. The reductive amination-based fluorescent labeling of HNE adducts is a simple and accurate technique that may be widely used to reveal increased levels of covalently modified proteins with HNE and its related aldehydes during aging and disease. (C) 2011 Elsevier Inc. All rights reserved.