peptide mass fingerprinting (http://www.matrixscience.com/cgi/search_form.pl
?FORMVER=2&SEARCH=PMF), a search engine that employs MS data to identify proteins
from the NCBInr database. The taxonomy for these searcheswas limited to Rattus
norvegicus. The database allowed up to one missed cleavage, and the mass tolerance
was set as 75 ppm peptide limited by fixed modification of carbamidomethyl
and variable modification of oxidation with monoisotopic values. Mascot reported
the molecular weight search (MOWSE) score, which is calculated by −10 × log10 (P),
where P is the probability that the observed match is a random event. The p value
is limited by the size of the sequence database being searched (limited by taxonomy),
the conditions, and the settings of the trypsin digestion. Each calculated value
that falls within a given mass tolerance of an experimental value counts as a match.
The accepted threshold is that an event is significant when it would be expected
to occur at random with a frequency of <5%. In this study, a protein match with a
score of >61 was regarded as significant
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