Question

Q1: You have two short peptides: Peptide A) KVDFSA; Peptide B) IRGTKL a. Write the chemical structure of peptide A as it would appear at pH 7. Include all charges and begin from the N-terminus b. determine the net charge on each of the peptides at pH 2, 7, and 11 c. You would now like to separate the two peptides. You decide to use a cation exchange column at pH 7 A cation exchange column is composed of negatively charged molecules, ie. SO3-, that are covalently bound to a resin. The peptides interact with these molecules via ionic interactions. You add your mixture of peptides followed by an increasing amount of NaCl (this serves to weaken the ionic interactions). In what order do you expect the peptides to be eluted from the column? Why? d. Many proteins bind tightly to DNA. Based on what you know about the composition of DNA, name two amino acids from these two peptides you might expect to find interacting with DNA. Briefly explain (limit to one sentence) your choice.

Answer 1

Peptide TKCTKL Peptide KDDFs A Peplide IRGTKL Orderin Peptrer KDFSA wall eltr 6rst then pepticle KDFSA i o so it is wealy bound Foom above two pepêtdes Ayinine ane sine Can react witb DNA They can yct rug ipmic lan ka ke th nege hvely makj