For a given value of E, a given query sequence, and a single scoring scheme, the calculated value of the cutoff score S will be different when searching databases of different lengths. A statistical analysis is then performed to determine if these alignments are significant or if they just occurred by chance. In this way, distant, more subtle, relationships between sequences can be more easily identified. Amino acid substitution matrices from an information theoretic perspective. A protein alignment scoring system sensitive at all evolutionary distances.
Protein database searches for multiple alignments.
Basic local alignment search tool. Identification of protein coding regions by database similarity search. Amino acid substitution matrices from protein blocks. Methods for assessing the statistical significance of molecular sequence features by using general scoring schemes. All Rights Reserved.