| water

## Function

Smith-Waterman local alignment

## Description

water uses the Smith-Waterman algorithm (modified for speed enhancments) to calculate the local alignment.

The Smith-Waterman algorithm is a member of the class of algorithms that can calculate the best score and local alignment in the order of mn steps, (where 'n' and 'm' are the lengths of the two sequences). These dynamic programming algorithms were first developed for protein sequence comparison by Smith and Waterman, though similar methods were independently devised during the late 1960's and early 1970's for use in the fields of speech processing and computer science.

A local alignment searches for regions of local similarity between two sequences and need not include the entire length of the sequences. Local alignment methods are very useful for scanning databases or other circumsatnces when you wish to find matches between small regions of sequences, for example between protein domains.

Dynamic programming methods ensure the optimal local alignment by exploring all possible alignments and choosing the best. It does this by reading in a scoring matrix that contains values for every possible residue or nucleotide match. water finds an alignment with the maximum possible score where the score of an alignment is equal to the sum of the matches taken from the scoring matrix.

An important problem is the treatment of gaps, i.e., spaces inserted to optimise the alignment score. A penalty is subtracted from the score for each gap opened (the 'gap open' penalty) and a penalty is subtracted from the score for the total number of gap spaces multiplied by a cost (the 'gap extension' penalty).

Typically, the cost of extending a gap is set to be 5-10 times lower than the cost for opening a gap.

## Usage

Here is a sample session with water

    % water tsw:hba_human tsw:hbb_human
    Smith-Waterman local alignment.
    Gap opening penalty [10.0]:
    Gap extension penalty [0.5]:
    Output alignment [hba_human.water]:

Go to the input files for this example
Go to the output files for this example

## Command line arguments

       Mandatory qualifiers:
      [-sequencea]         sequence   Sequence USA
      [-seqall]            seqall     Sequence database USA
       -gapopen            float      The gap open penalty is the score taken away
                                      when a gap is created. The best value
                                      depends on the choice of comparison matrix.
                                      The default value assumes you are using the
                                      EBLOSUM62 matrix for protein sequences, and
                                      the EDNAFULL matrix for nucleotide
                                      sequences.
       -gapextend          float      The gap extension penalty is added to the
                                      standard gap penalty for each base or
                                      residue in the gap. This is how long gaps
                                      are penalized. Usually you will expect a few
                                      long gaps rather than many short gaps, so
                                      the gap extension penalty should be lower
                                      than the gap penalty. An exception is where
                                      one or both sequences are single reads with
                                      possible sequencing errors in which case you
                                      would expect many single base gaps. You can
                                      get this result by setting the gap open
                                      penalty to zero (or very low) and using the
                                      gap extension penalty to control gap
                                      scoring.
      [-outfile]           align      Output alignment file name

       Optional qualifiers:
       -datafile           matrixf    This is the scoring matrix file used when
                                      comparing sequences. By default it is the
                                      file 'EBLOSUM62' (for proteins) or the file
                                      'EDNAFULL' (for nucleic sequences). These
                                      files are found in the 'data' directory of
                                      the EMBOSS installation.

       Advanced qualifiers:
       -[no]brief          boolean    Brief identity and similarity

       Associated qualifiers:
      "-sequencea" related qualifiers
       -sbegin1             integer    First base used
       -send1               integer    Last base used, def=seq length
       -sreverse1           boolean    Reverse (if DNA)
       -sask1               boolean    Ask for begin/end/reverse
       -snucleotide1        boolean    Sequence is nucleotide
       -sprotein1           boolean    Sequence is protein
       -slower1             boolean    Make lower case
       -supper1             boolean    Make upper case
       -sformat1            string     Input sequence format
       -sopenfile1          string     Input filename
       -sdbname1            string     Database name
       -sid1                string     Entryname
       -ufo1                string     UFO features
       -fformat1            string     Features format
       -fopenfile1          string     Features file name
      "-seqall" related qualifiers
       -sbegin2             integer    First base used
       -send2               integer    Last base used, def=seq length
       -sreverse2           boolean    Reverse (if DNA)
       -sask2               boolean    Ask for begin/end/reverse
       -snucleotide2        boolean    Sequence is nucleotide
       -sprotein2           boolean    Sequence is protein
       -slower2             boolean    Make lower case
       -supper2             boolean    Make upper case
       -sformat2            string     Input sequence format
       -sopenfile2          string     Input filename
       -sdbname2            string     Database name
       -sid2                string     Entryname
       -ufo2                string     UFO features
       -fformat2            string     Features format
       -fopenfile2          string     Features file name
      "-outfile" related qualifiers
       -aformat3            string     Alignment format
       -aopenfile3          string     Alignment file name
       -aextension3         string     File name extension
       -adirectory3         string     Output directory
       -aname3              string     Base file name
       -awidth3             integer    Alignment width
       -aaccshow3           boolean    Show accession number in the header
       -adesshow3           boolean    Show description in the header
       -ausashow3           boolean    Show the full USA in the alignment
       -aglobal3            boolean    Show the full sequence in alignment

       General qualifiers:
       -auto                boolean    Turn off prompts
       -stdout              boolean    Write standard output
       -filter              boolean    Read standard input, write standard output
       -options             boolean    Prompt for required and optional values
       -debug               boolean    Write debug output to program.dbg
       -acdlog              boolean    Write ACD processing log to program.acdlog
       -acdpretty           boolean    Rewrite ACD file as program.acdpretty
       -acdtable            boolean    Write HTML table of options
       -verbose             boolean    Report some/full command line options
       -help                boolean    Report command line options. More
                                      information on associated and general
                                      qualifiers can be found with -help -verbose
       -warning             boolean    Report warnings
       -error               boolean    Report errors
       -fatal               boolean    Report fatal errors
       -die                 boolean    Report deaths

Mandatory qualifiers | Allowed values | Default
--- | --- | ---
[-sequencea] (Parameter 1) | Sequence USA | Readable sequence | Required
[-seqall] (Parameter 2) | Sequence database USA | Readable sequence(s) | Required
-gapopen | The gap open penalty is the score taken away when a gap is created. The best value depends on the choice of comparison matrix. The default value assumes you are using the EBLOSUM62 matrix for protein sequences, and the EDNAFULL matrix for nucleotide sequences. | Number from 1.000 to 100.000 | 10.0 for any sequence
-gapextend | The gap extension penalty is added to the standard gap penalty for each base or residue in the gap. This is how long gaps are penalized. Usually you will expect a few long gaps rather than many short gaps, so the gap extension penalty should be lower than the gap penalty. An exception is where one or both sequences are single reads with possible sequencing errors in which case you would expect many single base gaps. You can get this result by setting the gap open penalty to zero (or very low) and using the gap extension penalty to control gap scoring. | Number from 0.100 to 10.000 | 0.5 for any sequence
[-outfile] (Parameter 3) | Output alignment file name | Alignment output file |
Optional qualifiers | Allowed values | Default
-datafile | This is the scoring matrix file used when comparing sequences. By default it is the file 'EBLOSUM62' (for proteins) or the file 'EDNAFULL' (for nucleic sequences). These files are found in the 'data' directory of the EMBOSS installation. | Comparison matrix file in EMBOSS data path | EBLOSUM62 for protein EDNAFULL for DNA
Advanced qualifiers | Allowed values | Default
-[no]brief | Brief identity and similarity | Boolean value Yes/No | Yes

## Input file format

water reads any two sequence USAs of the same type (DNA or protein).

### Input files for usage example

'tsw:hba_human' is a sequence entry in the example protein database 'tsw'

### Database entry: tsw:hba_human

    ID   HBA_HUMAN      STANDARD;      PRT;   141 AA.
    AC   P01922;
    DT   21-JUL-1986 (Rel. 01, Created)
    DT   21-JUL-1986 (Rel. 01, Last sequence update)
    DT   15-JUL-1999 (Rel. 38, Last annotation update)
    DE   HEMOGLOBIN ALPHA CHAIN.
    GN   HBA1 AND HBA2.
    OS   Homo sapiens (Human), Pan troglodytes (Chimpanzee), and
    OS   Pan paniscus (Pygmy chimpanzee) (Bonobo).
    OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Mammalia;
    OC   Eutheria; Primates; Catarrhini; Hominidae; Homo.
    RN   [1]
    RP   SEQUENCE FROM N.A. (ALPHA-1).
    RX   MEDLINE; 81088339.
    RA   MICHELSON A.M., ORKIN S.H.;
    RT   "The 3' untranslated regions of the duplicated human alpha-globin
    RT   genes are unexpectedly divergent.";
    RL   Cell 22:371-377(1980).
    RN   [2]
    RP   SEQUENCE FROM N.A. (ALPHA-2).
    RX   MEDLINE; 81175088.
    RA   LIEBHABER S.A., GOOSSENS M.J., KAN Y.W.;
    RT   "Cloning and complete nucleotide sequence of human 5'-alpha-globin
    RT   gene.";
    RL   Proc. Natl. Acad. Sci. U.S.A. 77:7054-7058(1980).
    RN   [3]
    RP   SEQUENCE FROM N.A. (ALPHA-2).
    RX   MEDLINE; 80137531.
    RA   WILSON J.T., WILSON L.B., REDDY V.B., CAVALLESCO C., GHOSH P.K.,
    RA   DERIEL J.K., FORGET B.G., WEISSMAN S.M.;
    RT   "Nucleotide sequence of the coding portion of human alpha globin
    RT   messenger RNA.";
    RL   J. Biol. Chem. 255:2807-2815(1980).
    RN   [4]
    RP   SEQUENCE FROM N.A. (ALPHA-1 AND ALPHA-2).
    RA   FLINT J., HIGGS D.R.;
    RL   Submitted (JAN-1997) to the EMBL/GenBank/DDBJ databases.
    RN   [5]
    RP   SEQUENCE.
    RA   BRAUNITZER G., GEHRING-MULLER R., HILSCHMANN N., HILSE K., HOBOM G.,
    RA   RUDLOFF V., WITTMANN-LIEBOLD B.;
    RT   "The constitution of normal adult human haemoglobin.";
    RL   Hoppe-Seyler's Z. Physiol. Chem. 325:283-286(1961).
    RN   [6]
    RP   SEQUENCE.
    RA   HILL R.J., KONIGSBERG W.;
    RT   "The structure of human hemoglobin: IV. The chymotryptic digestion of
    RT   the alpha chain of human hemoglobin.";
    RL   J. Biol. Chem. 237:3151-3156(1962).
    RN   [7]

      [Part of this file has been deleted for brevity]

    FT                                /FTId=VAR_002841.
    FT   VARIANT     130    130       A -> D (IN YUDA; O2 AFFINITY DOWN).
    FT                                /FTId=VAR_002842.
    FT   VARIANT     131    131       S -> P (IN QUESTEMBERT; HIGHLY UNSTABLE;
    FT                                CAUSES ALPHA-THALASSEMIA).
    FT                                /FTId=VAR_002843.
    FT   VARIANT     133    133       S -> R (IN VAL DE MARNE; O2 AFFINITY UP).
    FT                                /FTId=VAR_002844.
    FT   VARIANT     135    135       V -> E (IN PAVIE).
    FT                                /FTId=VAR_002845.
    FT   VARIANT     136    136       L -> M (IN CHICAGO).
    FT                                /FTId=VAR_002846.
    FT   VARIANT     136    136       L -> P (IN BIBBA; UNSTABLE;
    FT                                CAUSES ALPHA-THALASSEMIA).
    FT                                /FTId=VAR_002847.
    FT   VARIANT     138    138       S -> P (IN ATTLEBORO; O2 AFFINITY UP).
    FT                                /FTId=VAR_002848.
    FT   VARIANT     139    139       K -> E (IN HANAKAMI; O2 AFFINITY UP).
    FT                                /FTId=VAR_002849.
    FT   VARIANT     139    139       K -> T (IN TOKONAME; O2 AFFINITY UP).
    FT                                /FTId=VAR_002850.
    FT   VARIANT     140    140       Y -> H (IN ROUEN; O2 AFFINITY UP).
    FT                                /FTId=VAR_002851.
    FT   VARIANT     141    141       R -> C (IN NUNOBIKI; O2 AFFINITY UP).
    FT                                /FTId=VAR_002852.
    FT   VARIANT     141    141       R -> L (IN LEGNANO; O2 AFFINITY UP).
    FT                                /FTId=VAR_002853.
    FT   VARIANT     141    141       R -> H (IN SURESNES; O2 AFFINITY UP).
    FT                                /FTId=VAR_002854.
    FT   VARIANT     141    141       R -> P (IN SINGAPORE).
    FT                                /FTId=VAR_002855.
    FT   HELIX         4     35
    FT   HELIX        37     42
    FT   TURN         44     45
    FT   TURN         50     51
    FT   HELIX        53     71
    FT   TURN         72     74
    FT   HELIX        76     79
    FT   TURN         80     80
    FT   HELIX        81     89
    FT   TURN         90     91
    FT   TURN         95     95
    FT   HELIX        96    112
    FT   TURN        114    116
    FT   HELIX       119    136
    FT   TURN        137    139
    SQ   SEQUENCE   141 AA;  15126 MW;  5EC7DB1E CRC32;
         VLSPADKTNV KAAWGKVGAH AGEYGAEALE RMFLSFPTTK TYFPHFDLSH GSAQVKGHGK
         KVADALTNAV AHVDDMPNAL SALSDLHAHK LRVDPVNFKL LSHCLLVTLA AHLPAEFTPA
         VHASLDKFLA SVSTVLTSKY R
    //

### Database entry: tsw:hbb_human

    ID   HBB_HUMAN      STANDARD;      PRT;   146 AA.
    AC   P02023;
    DT   21-JUL-1986 (Rel. 01, Created)
    DT   21-JUL-1986 (Rel. 01, Last sequence update)
    DT   15-JUL-1999 (Rel. 38, Last annotation update)
    DE   HEMOGLOBIN BETA CHAIN.
    GN   HBB.
    OS   Homo sapiens (Human), Pan troglodytes (Chimpanzee), and
    OS   Pan paniscus (Pygmy chimpanzee) (Bonobo).
    OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Mammalia;
    OC   Eutheria; Primates; Catarrhini; Hominidae; Homo.
    RN   [1]
    RP   SEQUENCE.
    RC   SPECIES=HUMAN;
    RA   BRAUNITZER G., GEHRING-MULLER R., HILSCHMANN N., HILSE K., HOBOM G.,
    RA   RUDLOFF V., WITTMANN-LIEBOLD B.;
    RT   "The constitution of normal adult human haemoglobin.";
    RL   Hoppe-Seyler's Z. Physiol. Chem. 325:283-286(1961).
    RN   [2]
    RP   SEQUENCE FROM N.A.
    RC   SPECIES=HUMAN;
    RX   MEDLINE; 81064667.
    RA   LAWN R.M., EFSTRATIADIS A., O'CONNELL C., MANIATIS T.;
    RT   "The nucleotide sequence of the human beta-globin gene.";
    RL   Cell 21:647-651(1980).
    RN   [3]
    RP   SEQUENCE OF 121-146 FROM N.A.
    RC   SPECIES=HUMAN;
    RX   MEDLINE; 85205333.
    RA   LANG K.M., SPRITZ R.A.;
    RT   "Cloning specific complete polyadenylylated 3'-terminal cDNA
    RT   segments.";
    RL   Gene 33:191-196(1985).
    RN   [4]
    RP   X-RAY CRYSTALLOGRAPHY (2.5 ANGSTROMS) OF DEOXYHEMOGLOBIN.
    RC   SPECIES=HUMAN;
    RX   MEDLINE; 76027820.
    RA   FERMI G.;
    RT   "Three-dimensional fourier synthesis of human deoxyhaemoglobin at
    RT   2.5-A resolution: refinement of the atomic model.";
    RL   J. Mol. Biol. 97:237-256(1975).
    RN   [5]
    RP   SEQUENCE.
    RC   SPECIES=P.TROGLODYTES;
    RX   MEDLINE; 66071496.
    RA   RIFKIN D.B., KONIGSBERG W.;
    RT   "The characterization of the tryptic peptides from the hemoglobin of
    RT   the chimpanzee (Pan troglodytes).";
    RL   Biochim. Biophys. Acta 104:457-461(1965).
    RN   [6]

      [Part of this file has been deleted for brevity]

    FT   VARIANT     140    140       A -> T (IN ST JACQUES: O2 AFFINITY UP).
    FT                                /FTId=VAR_003081.
    FT   VARIANT     140    140       A -> V (IN PUTTELANGE; POLYCYTHEMIA;
    FT                                O2 AFFINITY UP).
    FT                                /FTId=VAR_003082.
    FT   VARIANT     141    141       L -> R (IN OLMSTED; UNSTABLE).
    FT                                /FTId=VAR_003083.
    FT   VARIANT     142    142       A -> D (IN OHIO; O2 AFFINITY UP).
    FT                                /FTId=VAR_003084.
    FT   VARIANT     143    143       H -> D (IN RANCHO MIRAGE).
    FT                                /FTId=VAR_003085.
    FT   VARIANT     143    143       H -> Q (IN LITTLE ROCK; O2 AFFINITY UP).
    FT                                /FTId=VAR_003086.
    FT   VARIANT     143    143       H -> P (IN SYRACUSE; O2 AFFINITY UP).
    FT                                /FTId=VAR_003087.
    FT   VARIANT     143    143       H -> R (IN ABRUZZO; O2 AFFINITY UP).
    FT                                /FTId=VAR_003088.
    FT   VARIANT     144    144       K -> E (IN MITO; O2 AFFINITY UP).
    FT                                /FTId=VAR_003089.
    FT   VARIANT     145    145       Y -> C (IN RAINIER; O2 AFFINITY UP).
    FT                                /FTId=VAR_003090.
    FT   VARIANT     145    145       Y -> H (IN BETHESDA; O2 AFFINITY UP).
    FT                                /FTId=VAR_003091.
    FT   VARIANT     146    146       H -> D (IN HIROSHIMA; O2 AFFINITY UP).
    FT                                /FTId=VAR_003092.
    FT   VARIANT     146    146       H -> L (IN COWTOWN; O2 AFFINITY UP).
    FT                                /FTId=VAR_003093.
    FT   VARIANT     146    146       H -> P (IN YORK; O2 AFFINITY UP).
    FT                                /FTId=VAR_003094.
    FT   VARIANT     146    146       H -> Q (IN KODAIRA; O2 AFFINITY UP).
    FT                                /FTId=VAR_003095.
    FT   HELIX         5     15
    FT   TURN         16     17
    FT   HELIX        20     34
    FT   HELIX        36     41
    FT   HELIX        43     45
    FT   HELIX        51     55
    FT   TURN         56     56
    FT   HELIX        58     75
    FT   TURN         76     77
    FT   HELIX        78     94
    FT   TURN         95     96
    FT   TURN        100    100
    FT   HELIX       101    121
    FT   HELIX       124    142
    FT   TURN        143    144
    SQ   SEQUENCE   146 AA;  15867 MW;  EC9744C9 CRC32;
         VHLTPEEKSA VTALWGKVNV DEVGGEALGR LLVVYPWTQR FFESFGDLST PDAVMGNPKV
         KAHGKKVLGA FSDGLAHLDN LKGTFATLSE LHCDKLHVDP ENFRLLGNVL VCVLAHHFGK
         EFTPPVQAAY QKVVAGVANA LAHKYH
    //

## Output file format

The output is a standard EMBOSS alignment file.

The results can be output in one of several styles by using the command-line qualifier -aformat xxx, where 'xxx' is replaced by the name of the required format. Some of the alignment formats can cope with an unlimited number of sequences, while others are only for pairs of sequences.

The available multiple alignment format names are: unknown, multiple, simple, fasta, msf, trace, srs

The available pairwise alignment format names are: pair, markx0, markx1, markx2, markx3, markx10, srspair, score

See: http://www.uk.embnet.org/Software/EMBOSS/Themes/AlignFormats.html for further information on alignment formats.

### Output files for usage example

### File: hba_human.water

    ########################################
    # Program:  water
    # Rundate:  Thu May 22 11:00:10 2003
    # Align_format: srspair
    # Report_file: hba_human.water
    ########################################
    #=======================================
    #
    # Aligned_sequences: 2
    # 1: HBA_HUMAN
    # 2: HBB_HUMAN
    # Matrix: EBLOSUM62
    # Gap_penalty: 10.0
    # Extend_penalty: 0.5
    #
    # Length: 145
    # Identity:      63/145 (43.4%)
    # Similarity:    88/145 (60.7%)
    # Gaps:           8/145 ( 5.5%)
    # Score: 293.5
    #
    #
    #=======================================

    HBA_HUMAN          2 LSPADKTNVKAAWGKVGAHAGEYGAEALERMFLSFPTTKTYFPHF-DLS-     49
                         |:|.:|:.|.|.||||  :..|.|.|||.|:.:.:|.|:.:|..| |||
    HBB_HUMAN          3 LTPEEKSAVTALWGKV--NVDEVGGEALGRLLVVYPWTQRFFESFGDLST     50

    HBA_HUMAN         50 ----HGSAQVKGHGKKVADALTNAVAHVDDMPNALSALSDLHAHKLRVDP     95
                             .|:.:||.|||||..|.::.:||:|::....:.||:||..||.|||
    HBB_HUMAN         51 PDAVMGNPKVKAHGKKVLGAFSDGLAHLDNLKGTFATLSELHCDKLHVDP    100

    HBA_HUMAN         96 VNFKLLSHCLLVTLAAHLPAEFTPAVHASLDKFLASVSTVLTSKY    140
                         .||:||.:.|:..||.|...||||.|.|:..|.:|.|:..|..||
    HBB_HUMAN        101 ENFRLLGNVLVCVLAHHFGKEFTPPVQAAYQKVVAGVANALAHKY    145

    #---------------------------------------
    #---------------------------------------

The Identity: is the percentage of identical matches between the two sequences over the reported aligned region (including any gaps in the length).

The Similarity: is the percentage of matches between the two sequences over the reported aligned region (including any gaps in the length).

## Data files

For protein sequences EBLOSUM62 is used for the substitution matrix. For nucleotide sequence, EDNAFULL is used. Others can be specified.

EMBOSS data files are distributed with the application and stored in the standard EMBOSS data directory, which is defined by EMBOSS environment variable EMBOSS_DATA.

Users can provide their own data files in their own directories. Project specific files can be put in the current directory, or for tidier directory listings in a subdirectory called ".embossdata". Files for all EMBOSS runs can be put in the user's home directory, or again in a subdirectory called ".embossdata".

The directories are searched in the following order:

- . (your current directory)
- .embossdata (under your current directory)
- ~/ (your home directory)
- ~/.embossdata

## Notes

water is a true implementation of the Smith-Waterman algorithm and so produces a full path matrix. It therefore cannot be used with genome sized sequences unless you have a lot of memory and a lot of time.

## References

1. Smith TF, Waterman MS (1981) J. Mol. Biol 147(1);195-7

## Warnings

Local alignment methods only report the best matching areas between two sequences - there may be a large number of alternative local alignments that do not score as highly. If two proteins share more than one common region, for example one has a single copy of a particular domain while the other has two copies, it may be possible to "miss" the second and subsequent alignments. You will be able to see this situation if you have done a dotplot and your local alignment does not show all the features you expected to see.

water is for aligning the best matching subsequences of two sequences. It does not necessarily align whole sequences against each other; you should use needle if you wish to align closely related sequences along their whole lengths.

A true Smith Waterman implementation like water needs memory proportional to the product of the sequence lengths. For two sequences of length 10,000,000 and 1,000 it therefore needs memory proportional to 10,000,000,000 characters. Two arrays of this size are produced, one of ints and one of floats so multiply that figure by 8 to get the memory usage in bytes. That doesn't include other overheads. Therefore only use water and needle for accurate alignment of reasonably short sequences.

If you run out of memory, try using supermatcher or matcher.

## Diagnostic Error Messages

    Uncaught exception
     Assertion failed
     raised at ajmem.c:xxx

Probably means you have run out of memory. Try using supermatcher or matcher if this happens.

## Exit status

0 if successful.

## Known bugs

None.

## See also

Program name | Description
--- | ---
matcher | Finds the best local alignments between two sequences
seqmatchall | Does an all-against-all comparison of a set of sequences
supermatcher | Finds a match of a large sequence against one or more sequences
wordmatch | Finds all exact matches of a given size between 2 sequences

matcher is a local alignment program that gives as good an alignment as

water

but it uses far less memory. However,

water

runs twice as fast as matcher.

supermatcher is designed for local alignments of very large sequences. It gives good results as long as there is not significant amounts of insertion or deletion in the alignment.

supermatcher Finds a match of a large sequence against one or more sequences matcher Finds the best local alignments between two sequences

## Author(s)

Alan Bleasby (ableasby © hgmp.mrc.ac.uk)
HGMP-RC, Genome Campus, Hinxton, Cambridge CB10 1SB, UK

## History

    Completed 7th July 1999.
    Modified 27th July 1999 - tweaking scoring.
    Modified 22 Oct 2000 - added ID and Similarity scores.

## Target users

This program is intended to be used by everyone and everything, from naive users to embedded scripts.

## Comments