<p class="first" id="d1213709e133">Exposure of biological molecules to oxidants is
inevitable and therefore commonplace.
Oxidative stress in cells arises from both external agents and endogenous processes
that generate reactive species, either purposely (
<i>e.g.</i> during pathogen killing or enzymatic reactions) or accidentally (
<i>e.g.</i> exposure to radiation, pollutants, drugs, or chemicals). As proteins are
highly abundant
and react rapidly with many oxidants, they are highly susceptible to, and major targets
of, oxidative damage. This can result in changes to protein structure, function, and
turnover and to loss or (occasional) gain of activity. Accumulation of oxidatively-modified
proteins, due to either increased generation or decreased removal, has been associated
with both aging and multiple diseases. Different oxidants generate a broad, and sometimes
characteristic, spectrum of post-translational modifications. The kinetics (rates)
of damage formation also vary dramatically. There is a pressing need for reliable
and robust methods that can detect, identify, and quantify the products formed on
amino acids, peptides, and proteins, especially in complex systems. This review summarizes
several advances in our understanding of this complex chemistry and highlights methods
that are available to detect oxidative modifications—at the amino acid, peptide, or
protein level—and their nature, quantity, and position within a peptide sequence.
Although considerable progress has been made in the development and application of
new techniques, it is clear that further development is required to fully assess the
relative importance of protein oxidation and to determine whether an oxidation is
a cause, or merely a consequence, of injurious processes.
</p>