HELP NEEDED

[STELLA2 at ROMA1.infn.it]

I have to start a new research project in fluorescence spectroscopy
of proteins. Therefore I would like to  find out wich of the proteins with 
known sequence contain only one triptophan (and no matter how many
tyrosines) and wich contain a single tyrosine and no triptophan.
Does such a list already exist? Is it possible to do such a search
in the protein sequences data banks and if yes how?
Thank you for your help,
Lorenzo Stella
 
Lorenzo Stella
University of Rome "La Sapienza", Italy
E-Mail STELLA2 at VAXROM.ROMA1.INFN.IT