Question 3 of 17 Incorrect Incorrect Map Sapling Learning macmillan learning Pep

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Question 3 of 17 Incorrect Incorrect Map Sapling Learning macmillan learning Peptides can be separated using an ion-exchange column based on their isoelectric (pl) values. At which pH values would two different peptides, one with a pl of 5.7 and the other with a pl of 9.4, bind to a cation- and anion-exchange column? Each peptide may be capable of binding to each column at more than one pH value Peptide BPeptide A pl = 9.4 pl = 5.7 anion-exchange column at cation-exchange column at pH 3.6 pH = 3.6 Peptide A pl = 5.7 Peptide B pl = 9.4 Incorrect pH 6.5 lies between the pl values of the two peptides, meaning that one will be positively charged and one will be negatively charged. Glven that negatively-charged species bind to the anion-exchange column, consider which of the two peptides will bind to the anion-exchange column at pH 6.5 pH 6.5 pH = 6.5 Peptide B pl= 9.4 Peptide A pl = 5.7 pH 10.1 pH 10.1 Peptide A pl = 5.7 Previous Try Again Next Exit

Explanation / Answer

pI --> isoelectric point, pH in which charges of COO- and NH4+ are the same

if pH is less than pI --> positive charge; binds to cation exchangers

if pH is more than pI --> negtively charge; binds to anions exhcangers

then...

For Protein A; Anion Exchanger:

a) pH = 3.6, Peptide A (pI = 5.7), Positive charge --> no bind

b) pH = 6.5, Peptide A (pI = 5.7), Negative Charge -->  binds

c) pH = 10.1, Peptide A (pI = 5.7), Negative charge --> bind

For Protein A; Canion Exchanger:

a) pH = 3.6, Peptide A (pI = 5.3), Positive charge --> binds

b) pH = 6.5, Peptide A (pI = 5.3), Negative Charge --> will not bind

c) pH = 10.1, Peptide A (pI = 5.3), Negative charge --> will not bind

For Protein B; Anion Exchanger:

a) pH = 3.6, Peptide B (pI = 8.7), Positive charge --> no bind

b) pH = 6.5, Peptide B (pI = 8.7), Positive charge --> no bind

c) pH = 10.1, Peptide B (pI = 8.7), Negative charge --> will bind

For Protein B; Canion Exchanger:

a) pH = 3.6, Peptide B (pI = 8.7), Positive charge --> binds

b) pH = 6.5, Peptide B (pI = 8.7), Positive charge --> binds

c) pH = 10.1, Peptide B (pI = 8.7), Positive charge --> no bind

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