Isoelectric Point: also known as pI; pH at which a peptide carries no net electrical charge or is electrically neutral
• pH < pI: net charge is positive
• pH = pI: net charge is zero
• pH > pI: net charge is negative
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 5.0 and the other with a pI of 9.4, bind to a caution- and anion-exchange column? Each peptide may be capable of binding to each column at more than one pH value.