If the side chain of a glutamic acid residue has a pKa of 4.1, at pH 6.1 the ratio of uncharged to charged side chain would be about

A. 100:1
B. 10:1
C. 1:1
D. 1:10
E. 1:100

To determine the ratio of uncharged to charged side chain at pH 6.1, we need to compare the pH to the pKa value of the side chain.

The pKa value represents the pH at which half of the molecules of the compound are ionized, and half are in their uncharged form.

In this case, the pKa of the side chain of a glutamic acid residue is given as 4.1.

Since pH 6.1 is higher than the pKa of 4.1, the pH is closer to neutral, which means the proportion of charged to uncharged side chain will be relatively low.

As a general rule, when the pH is two units above or below the pKa value, the ratio of charged to uncharged form is approximately 10:1.

Since pH 6.1 is approximately two units above the pKa of 4.1, we can estimate that the ratio of uncharged to charged side chain would be approximately 10:1.

Therefore, the answer is B. 10:1.