what order, first to last, would the amino acids Lys, Glu and His elute from an anion exchange column at pH 6.0? First__ Second__ Third__
The order of elution is Lys, His and Glu.
Anion exchange colums consists of positively charge resins, which binds negetively charged molecules, displacing the counter ion.
At Ph 6, net charge on Lys side chain is +ve because its pKa value is 10.54,
Glu side chain will be negetively charged by donating its proton at pH 6 (pKa 4.25)
His has zero charge at pH 6 because for His, pH = pKa = 6
Hence Glu binds with anion exchange column therefore elute last and Lys elute first because of repulsion, and due to zero charge on His it will elute in between Lys and Glu.
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