BLOSUM
From Bioinformatics.Org Wiki
BLOSUM (“Blocks Amino Acid Substitution Matrices”) matrices were developed for a range of changes. They were determined by local alignments. The BLOSUM number represents a derivation from a sequence of that percent change or greater, so BLOSUM62 corresponds to a change of 62% or greater Distantly related proteins can be compared directly with the BLOSUM matrix, as empirical data were used in the development of the matrices.