# Blosum matrix example

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*2020-02-24 10:41*

The clustering step in BLOSUM matrix construction has two purposes: parameterizing evo lutionary divergence, via the percent identity parameter, n, and accounting for sample bias. The use of clusters in tabulating the incidence of amino acid pairs in the data contributes to these goals in several ways.This MATLAB function returns a BLOSUM (Blocks Substitution Matrix) scoring matrix with a specified percent identity. blosum matrix example

BLOSUM matrices are derived from blocks whose alignment corresponds to the BLOSUM, matrix number (e. g. BLOSUM 62 is derived from Blocks containing 62 identity in ungapped sequence alignment) BLOSUM 62 is the default matrix for the standard protein BLAST program

By using the scoring matrix (substitution matrix) to score the comparison of each residue pair, there are 20 3 possible match scores for a 3letter word. For example, the score obtained by comparing PQG with PEG and PQA is 15 and 12, respectively with the BLOSUM62 weighting scheme. A BLOSUM tells us the likelihood of occurrence of each pairwise substitution, and we can use these values to score a pairwise comparison. Each scoring matrix is constructed based on how identical the ungapped multiple sequence alignments are. For example, BLOSUM62 is derived from**blosum matrix example** BLOSUM is the widely used AA substitution matrix BLOSUM62 (Henikoff& Henikoff, 1992), CLESUM is the local structure substitution matrix, d(i, j) measures the spatial proximity of two aligned residues after rigidbody superposition with a reciprocallike cRMS form (see Eq.