Protein Sequencing: A student is sequencing a short peptide using the Sanger method. Based on the experimental results, write out the complete peptide structure using $3$ letter amino acid abbreviations and showing all covalent bonds between amino acids.

Experimental Results:

The peptide hormone was treated with DNFB$,$ followed by hydrolysis and amino acid analysis.

Results: DNP$-$ Ala

Free aa: Ala, Arg, Asp, Lys$,$ Phe, Ser, Val

$2.$ The peptide hormone was treated with Trypsin. Two peptides $($A & B$)$ were separated, treated with DNFB$,$ followed by hydrolysis and amino acid analysis.

Peptide A Results: DNP$-$Ala and free aa: Arg, Asp, Val

Peptide B Results: DNP$-$Ser and free aa: Ala, Lys$,$ Phe

$3.$ The peptide hormone was treated with Chymotrypsin. One peptide and a free amino acid were separated. The peptide treated with DNFB$,$ followed by hydrolysis and amino acid analysis.

Free Amino acid: Lys

Peptide A Results: DNP$-$Ala and free aa: Ala, Arg, Asp, Phe, Ser, Val

$4.$ The peptide hormone was treated with Asp$-$N$-$Protease: Two peptides $($A & B$)$ were separated, treated with DNFB$,$ followed by hydrolysis and amino acid analysis.

Peptide A Results: DNP$-$Ala and free aa: Val

Peptide B Results: DNP$-$Asp and free aa: Ala, Arg, Lys$,$ Phe, Ser