explain how #14 was obtained

13. What is the name of the adjacent peptide? Use the one-letter code for amino acids to report your answer. (Please note that the protonation state of this peptide as shown - is unusual.) DSR Y 14. Considering the peptide shown above, what would be the net charge of this peptide at pH=12.5 ? To facilitate answering this question, assume that the N-terminal aminium group has a pK, of 8 , the C-terminal carboxyl group has a pK3 of 3.5, and the acidic forms of ionizable side chains have pK2s as follows: Asp =4.0,Glu=4.0, His =6,Cys=8.4, Tyr=10, Lys =10, and Arg = 12.5. Also, assume that if the pH is at least two units above or below the pK,of a particular group, then that group is completely unprotonated or protonated, as the case may be. NetCh,=(1)(1)+(+1)(0)+(+1)(0.5)=2,5+(1)(1)+(1)(1)