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BLASTp, or Protein BLAST, is used to compare protein sequences. You can input one or more protein sequences that you want to compare against a single protein sequence or a database of protein sequences. This is useful when you're trying to identify a protein by finding similar sequences in existing protein databases. [17]
A BLAST variant called MegaBLAST indexes 4 databases to speed up alignments. [9] BLAT can extend on multiple perfect and near-perfect matches (default is 2 perfect matches of length 11 for nucleotide searches and 3 perfect matches of length 4 for protein searches), while BLAST extends only when one or two matches occur close together. [1] [9]
CS-BLAST greatly improves alignment quality over the entire range of sequence identities and especially for difficult alignments in comparison to regular BLAST and PSI-BLAST. PSI-BLAST (Position-Specific Iterated BLAST) runs at about the same speed per iteration as regular BLAST, but is able to detect weaker sequence similarities that are still ...
A sequence profiling tool in bioinformatics is a type of software that presents information related to a genetic sequence, gene name, or keyword input. Such tools generally take a query such as a DNA, RNA, or protein sequence or ‘keyword’ and search one or more databases for information related to that sequence. Summaries and aggregate ...
For instance, two protein sequences may be relatively similar but differ at certain intervals as one protein may have a different subunit compared to the other. Representing these differing sub-sequences as gaps will allow us to treat these cases as “good matches” even though there are long consecutive runs with indel operations in the ...
A profile HMM modelling a multiple sequence alignment. HMMER is a free and commonly used software package for sequence analysis written by Sean Eddy. [2] Its general usage is to identify homologous protein or nucleotide sequences, and to perform sequence alignments.
E.g., BLOSUM62 is the matrix built using sequences with less than 62% similarity (sequences with ≥ 62% identity were clustered together). Note: BLOSUM 62 is the default matrix for protein BLAST. Experimentation has shown that the BLOSUM-62 matrix is among the best for detecting most weak protein similarities. [1]
Recently, sequence context-specific amino acid similarities have been derived that do not need substitution matrices but that rely on a library of sequence contexts instead. Using this idea, a context-specific extension of the popular BLAST program has been demonstrated to achieve a twofold sensitivity improvement for remotely related sequences ...