BLAST Search main parameters

The statistical significance threshold for reporting matches against database sequences; the default value is 10 in NCBI-BLAST, such that 10 matches are expected to be found merely by chance, according to the stochastic model of Karlin and Altschul (1990). If the statistical significance ascribed to a match is greater than the EXPECT threshold, the match will not be reported. Lower EXPECT thresholds are more stringent, leading to fewer chance matches being reported. Fractional values are acceptable.

In our program, we set the default E-value 1e-5. The lower of the E-value is chosen, the more accurate the prediction will be.