Extra Credit Problem #2

If you want to work on this problem as a group project, that will be
okay (and even preferable).  Just turn in a solution with the names of
the group that participated in the solution.  You will get one point
for an honest attempt, two points for a correct solution.

To save time in sequencing, sometimes the Edman degradation procedure
can be run on a mixture of peptides without first separating them. 
The results are like a jigsaw puzzle which one can then piece together
to get the overall sequence.  The following data are sufficient to 
deduce a complete sequence for the small protein described.

1.   A small protein, containing only 40 amino acid residues was
reduced and carboxymethylated to alkylate the cysteine residues and
then characterized as follows:

(a) Edman degradation gave Asp as N-terminal.

(b) CNBr cleavage, followed by Edman sequencing of the
unfractionated mixture of peptides gave the following sets of amino
acids in each round of sequencing (each set listed in alphabetical
order; data beyond the 8th round were not reliable):

Round:          1    2    3    4    5    6    7    8

Amino          Arg  Gln  Asn  Arg  Asn  Arg  Ala  Ala
   Acids:      Asp  Pro  Pro  His  Ilu  His  Gly  Lys
               Glu  Thr  Ser  Ilu  Leu  Trp  Phe  Met
               Gly  Tyr  Tyr  Val  Phe  Val  Thr  Tyr

(c) Trypsin digestion followed by Edman sequencing of the
unfractionated mixture of peptides gave the following sets of amino
acids in each round of sequencing (each set listed in alphabetical
order; data beyond the 8th round were not reliable.): (Cys
indicates carboxymethylcysteine.)

Round:          1    2    3    4    5    6    7    8

Amino          Asp  Cys  His  Ala  Ilu  Arg  Cys  Glu
   Acids:      Gly  His  Met  Asn  Leu  Phe  Lys  Leu
               Gly  Pro  Thr  Glu  Thr  Ser  Ilu
               Phe  Pro  Tyr  Val  Trp  Ser
               Tyr  Tyr

Deduce the sequence of this 40-residue peptide from this
information.