is the overall charge of glu (glutamate) at a pH of 4.3 0?

I thought it would be since there is a (+) charge on the NH3, counteracted by the negative charge on the COO(-) group.

To determine the overall charge of a molecule at a specific pH, you need to consider the pKa values of its functional groups and the pH at which you want to calculate the charge.

In the case of glutamate (glu), it has two ionizable functional groups: the amino group (NH3+) and the carboxyl group (COO-). The pKa values of these groups will determine their protonation state at a given pH.

At a pH of 4.3, let's consider the pKa values:
- The pKa of the carboxyl group in glutamate is around 2.2.
- The pKa of the amino group in glutamate is around 9.7.

Now, for the carboxyl group: at a pH below its pKa (2.2), it will be predominantly in its protonated form (COOH) and have a positive charge. At a pH above its pKa, it will be predominantly in its deprotonated form (COO-) and have a negative charge. At a pH around 4.3 (higher than the pKa), the carboxyl group will be mostly deprotonated, carrying a negative charge.

For the amino group: at a pH below its pKa (9.7), it will be predominantly in its protonated form (NH3+) and have a positive charge. At a pH above its pKa, it will be predominantly in its deprotonated form (NH2) and have no charge. At a pH around 4.3 (lower than the pKa), the amino group will be mostly protonated, carrying a positive charge.

Considering both functional groups, at a pH of 4.3, the carboxyl group will be negatively charged (COO-) and the amino group will be positively charged (NH3+). Therefore, the overall charge of glutamate at a pH of 4.3 is not 0; it has a net charge of -1.