oddcomp was written to answer the question 'which proteins contain at least n X and m Y in p residues'.
One could search for serine rich or polyglutamine rich, collagen helix, or similar proteins using this program.
oddcomp takes as input an amino acid composition data file in the same format as the output from compseq. It can tolerate any word length within reason for the memory capacity of the machine in question. Only the first two fields in the composition data file are used: the word and the number of occurrences. Any word not mentioned is initialised to a threshold of zero.
oddcomp measures the amino acid composition (this can be dimers etc as well as monomers) in a sliding window. If and when composition meets or exceeds all the specified thresholds, the sequence is reported and oddcomp moves to the next sequence. It does not report where in the sequence it found the matching region, merely the sequence ID.
oddcomp was originally written to identify SR/RS containing proteins. eg. specifying a window of forty amino acids containing at least 3 SR and 4 RS words.
To search for a specific set of words in a sequence, edit the input composition data file to delete any words from the input file in which you are not interested. The search is a boolean AND so there must be (from the short example above) at least 3 SR AND at least 4 RS for the sequence to be reported. If your total words specified exceeds window-wordlength+1 you will never get any hits.
Only one word size can be used and is specified at the top of the file in compseq-style output.
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The columns "Obs Frequency", "Exp Frequency" and "Obs/Exp Frequency" are not required - they were simply included in this example to show the similarity between this input file format and the output of the program compseq. A compseq output file can be used as the input to oddcomp - the extra columns are ignored by oddcomp.
A minimal composition input data file would look like this:
Word size 2 Total count 0 RS 2 SR 1
Blank lines and lines starting with '#' are ignored.
The first non-comment line should start with 'Word size' and will specify the word size to use.
A line starting with the word 'Total' is required.
Anything after the line starting with the word 'Total' will be read as word count data.
Word count data consists of a word to search for and the count of that word to search for within the sliding window. The columns are separated by one or more spaces or TAB characters. Anything after these two columns will be ignored.