Separation, detection, and quantification of hydroperoxides formed at side-chain and backbone sites on amino acids, peptides, and proteins

TY - JOUR

T1 - Separation, detection, and quantification of hydroperoxides formed at side-chain and backbone sites on amino acids, peptides, and proteins

AU - Morgan, Philip E

AU - Pattison, David I

AU - Hawkins, Clare Louise

AU - Davies, Michael Jonathan

PY - 2008/11/1

Y1 - 2008/11/1

N2 - Hydroperoxides are major reaction products of radicals and singlet oxygen with amino acids, peptides, and proteins. However, there are few data on the distribution of hydroperoxides in biological samples and their sites of formation on peptides and proteins. In this study we show that normal-or reversed-phase gradient HPLC can be employed to separate hydroperoxides present in complex systems, with detection by postcolumn oxidation of ferrous xylenol orange to the ferric species and optical detection at 560 nm. The limit of detection (10-25 pmol) is comparable to chemiluminescence detection. This method has been used to separate and detect hydroperoxides, generated by hydroxyl radicals and singlet oxygen, on amino acids, peptides, proteins, plasma, and intact and lysed cells. In conjunction with EPR spin trapping and LC/MS/MS, we have obtained data on the sites of hydroperoxide formation. A unique fingerprint of hydroperoxides formed at alpha-carbon (backbone) positions has been identified; such backbone hydroperoxides are formed in significant yields only when the amino acid is part of a peptide or protein. Only side-chain hydroperoxides are detected with free amino acids. These data indicate that free amino acids are poor models of protein damage induced by radicals or other oxidants.

AB - Hydroperoxides are major reaction products of radicals and singlet oxygen with amino acids, peptides, and proteins. However, there are few data on the distribution of hydroperoxides in biological samples and their sites of formation on peptides and proteins. In this study we show that normal-or reversed-phase gradient HPLC can be employed to separate hydroperoxides present in complex systems, with detection by postcolumn oxidation of ferrous xylenol orange to the ferric species and optical detection at 560 nm. The limit of detection (10-25 pmol) is comparable to chemiluminescence detection. This method has been used to separate and detect hydroperoxides, generated by hydroxyl radicals and singlet oxygen, on amino acids, peptides, proteins, plasma, and intact and lysed cells. In conjunction with EPR spin trapping and LC/MS/MS, we have obtained data on the sites of hydroperoxide formation. A unique fingerprint of hydroperoxides formed at alpha-carbon (backbone) positions has been identified; such backbone hydroperoxides are formed in significant yields only when the amino acid is part of a peptide or protein. Only side-chain hydroperoxides are detected with free amino acids. These data indicate that free amino acids are poor models of protein damage induced by radicals or other oxidants.

KW - Amino Acids

KW - Animals

KW - Carbon

KW - Cell Line

KW - Chromatography, High Pressure Liquid

KW - Electron Spin Resonance Spectroscopy

KW - Humans

KW - Hydrogen Peroxide

KW - Hydroxyl Radical

KW - Mass Spectrometry

KW - Mice

KW - Peptides

KW - Proteins

U2 - 10.1016/j.freeradbiomed.2008.08.004

DO - 10.1016/j.freeradbiomed.2008.08.004

M3 - Journal article

C2 - 18762246

SN - 0891-5849

VL - 45

SP - 1279

EP - 1289

JO - Free Radical Biology & Medicine

JF - Free Radical Biology & Medicine

IS - 9

ER -