Final answer:
To calculate the net charge of a peptide at a specific pH, compare the pH to the pKa values of its functional groups. If the pH is lower than the pKa of an acidic group, it will be protonated and carry a positive charge.
Step-by-step explanation:
The net charge of a peptide at a specific pH can be determined by considering the ionization state of its functional groups. To calculate the net charge of a peptide at pH 4.7, you need to know the pKa values of the acidic and basic groups in the peptide. Using the Henderson-Hasselbalch equation, you can compare the pH to the pKa values to determine whether each group is protonated or deprotonated.
Let's assume the peptide has an acidic group with a pKa of 3.5 and a basic group with a pKa of 10.5.
If the pH is lower than the pKa of an acidic group, the group will be protonated and carry a positive charge (+1). If the pH is higher than the pKa of an acidic group, the group will be deprotonated and carry a negative charge (-1).
Similarly, if the pH is higher than the pKa of a basic group, the group will be deprotonated and carry a positive charge (+1). If the pH is lower than the pKa of a basic group, the group will be protonated and carry a negative charge (-1).
By considering the pH and the pKa values of the acidic and basic groups in the peptide, you can determine the net charge of the peptide at pH 4.7.
If the pH is higher than the pKa of an acidic group, it will be deprotonated and carry a negative charge. The same applies to basic groups, but in reverse.