edialign.txt

emboss的linux版本的源代码

                                 edialign 



Function

   Local multiple alignment of sequences

Description

   edialign is an EMBOSS version of the program DIALIGN2 by B.
   Morgenstern. It takes as input nucleic acid or protein sequences and
   produces as output a multiple sequence alignment. The sequences need
   not be similar over their complete length, since the program
   constructs alignments from gapfree pairs of similar segments of the
   sequences. Such segment pairs are referred to as "diagonals". If
   (possibly) coding nucleic acid sequences are to be aligned, edialign
   can optionally translate the compared "nucleic acid segments" to
   "peptide segments", or even perform comparisons at both nucleic acid
   and protein levels, so as to increase the sensitivity of the
   comparison.

Algorithm

   For a complete explanation of the algorithm, see the references. In
   short :

   As described in our papers, the program DIALIGN constructs alignments
   from gapfree pairs of similar segments of the sequences. Such segment
   pairs are referred to as "diagonals". Every possible diagonal is given
   a so-called weight reflecting the degree of similarity among the two
   segments involved. The overall score of an alignment is then defined
   as the sum of weights of the diagonals it consists of and the program
   tries to find an alignment with maximum score -- in other words : the
   program tries to find a consistent collection of diagonals with
   maximum sum of weights. This novel scoring scheme for alignments is
   the basic difference between DIALIGN and other global or local
   alignment methods. Note that DIALIGN does not employ any kind of gap
   penalty.

   It is possible to use a threshold T for the quality of the diagonals.
   In this case, a diagonal is considered for alignment only if its
   "weight" exceeds this threshold. Regions of lower similarity are
   ignored. In the first version of the program (DIALIGN 1), this
   threshold was in many situations absolutely necessary to obtain
   meaningful alignments. By contrast, DIALIGN 2 should produce
   reasonable alignments without a threshold, i.e. with T = 0. This is
   the most important difference between DIALIGN 2 and the first version
   of the program. Nevertheless, it is still possible to use a positive
   threshold T to filter out regions of lower significance and to include
   only high scoring diagonals into the alignment.

   The use of overlap weights improves the sensitivity of the program if
   multiple sequences are aligned but it also increases the running time,
   especially if large numbers of sequences are aligned. By default,
   "overlap weights" are used if up to 35 sequences are aligned but
   switched off for larger data sets.

   If (possibly) coding nucleic acid sequences are to be aligned, DIALIGN
   optionally translates the compared "nucleic acid segments" to "peptide
   segments" according to the genetic code -- without presupposing any of
   the three possible reading frames, so all combinations of reading
   frames get checked for significant similarity. If this option is used,
   the similarity among segments will be assessed on the "peptide level"
   rather than on the "nucleic acid level".

   For the levels of sequence similarity, release 2.2 of DIALIGN has two
   additional options:
     * It can measure the similarity among segment pairs at both levels
       of similarity (nucleotide-level and peptide-level similarity). The
       score of a fragment is based on whatever similarity is stronger.
       As a result, the program can now produce mixed alignments that
       contain both types of fragments. Fragments with stronger
       similarity at the "nucleotide level" are referred to as
       N-fragments whereas fragments with stronger similarity a the
       peptide level are called P-fragments.
     * If the translation or mixed alignment option is used, it is
       possible to consider the reverse complements of segments, too. In
       this case, both the original segments and their reverse
       complements are translated and both pairs of implied "peptide
       segments" are compared. This option is useful if DNA sequences
       contain coding regions not only on the "Watson strand" but also on
       the "Crick strand".

   The score that DIALIGN assigns to a fragment is based on the
   probability to find a fragment of the same respective length and
   number of matches (or BLOSUM values, if the translation option is
   used) in random sequences of the same length as the input sequences.
   If long genomic sequences are aligned, an iterative procedure can be
   applied where the program first looks for fragments with strong
   similarity. In subsequent steps, regions between these fragments are
   realigned. Here, the score of a fragment is based on random occurrence
   in these regions between the previously aligned segment pairs.

Usage

   Here is a sample session with edialign


% edialign 
Local multiple alignment of sequences
Input sequence set: vtest.seq
Output file [vtest.edialign]: 
(gapped) output sequence(s) [vtest.fasta]: 

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

Command line arguments

   Standard (Mandatory) qualifiers:
  [-sequences]         seqset     Sequence set filename and optional format,
                                  or reference (input USA)
  [-outfile]           outfile    [*.edialign] Output file name
  [-outseq]            seqoutall  [.] (Aligned) sequence
                                  set(s) filename and optional format (output
                                  USA)

   Additional (Optional) qualifiers (* if not always prompted):
*  -nucmode            menu       [n] Nucleic acid sequence alignment mode
                                  (simple, translated or mixed) (Values: n
                                  (simple); nt (translation); ma (mixed
                                  alignments))
*  -revcomp            boolean    [N] Also consider the reverse complement
   -overlapw           selection  [default (when Nseq =< 35)] By default
                                  overlap weights are used when Nseq =<35 but
                                  you can set this to 'yes' or 'no'
   -linkage            menu       [UPGMA] Clustering method to construct
                                  sequence tree (UPGMA, minimum linkage or
                                  maximum linkage) (Values: UPGMA (UPGMA); max
                                  (maximum linkage); min (minimum linkage))
   -maxfragl           integer    [40] Maximum fragment length (Integer 0 or
                                  more)
*  -fragmat            boolean    [N] Consider only N-fragment pairs that
                                  start with two matches
*  -fragsim            integer    [4] Consider only P-fragment pairs if first
                                  amino acid or codon pair has similarity
                                  score of at least n (Integer 0 or more)
   -itscore            boolean    [N] Use iterative score
   -threshold          float      [0.0] Threshold for considering diagonal for
                                  alignment (Number 0.000 or more)

   Advanced (Unprompted) qualifiers:
   -mask               boolean    [N] Replace unaligned characters by stars
                                  '*' rather then putting them in lowercase
   -dostars            boolean    [N] Activate writing of stars instead of
                                  numbers
   -starnum            integer    [4] Put up to n stars '*' instead of digits
                                  0-9 to indicate level of conservation
                                  (Integer 0 or more)

   Associated qualifiers:

   "-sequences" associated qualifiers
   -sbegin1            integer    Start of each sequence to be used
   -send1              integer    End of each sequence to be used
   -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
   -sdbname1           string     Database name
   -sid1               string     Entryname
   -ufo1               string     UFO features
   -fformat1           string     Features format
   -fopenfile1         string     Features file name

   "-outfile" associated qualifiers
   -odirectory2        string     Output directory

   "-outseq" associated qualifiers
   -osformat3          string     Output seq format
   -osextension3       string     File name extension
   -osname3            string     Base file name
   -osdirectory3       string     Output directory
   -osdbname3          string     Database name to add
   -ossingle3          boolean    Separate file for each entry
   -oufo3              string     UFO features
   -offormat3          string     Features format
   -ofname3            string     Features file name
   -ofdirectory3       string     Output directory

   General qualifiers:
   -auto               boolean    Turn off prompts
   -stdout             boolean    Write standard output
   -filter             boolean    Read standard input, write standard output
   -options            boolean    Prompt for standard and additional values
   -debug              boolean    Write debug output to program.dbg
   -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 dying program messages

Input file format

   edialign reads any normal sequence USAs. You must give as input at
   least two sequences. You can use proteins as well as nucleic acids,
   but you can't mix them.

  Input files for usage example