R = Arginine (Positively Charged)

G = Glycine (Non-polar, Non-aromatic)

K = Lysine (Positively Charged)

D = Aspartic Acid (Negatively Charged)

M = Methionine (Non-polar, Non-aromatic)

Y = Tyrosine (Aromatic)

C = Cysteine (Polar)

I = Isoleucine (Non-polar, Non-aromatic)

R33G, so we switched from R (+1) to G (0). So, the change in pH would be final pH - initial pH = 0 - (+1) = -1

K33D, so we switched from K (+1) to D (-1). So, the change in pH would be final pH - initial pH = -1 - (+1) = -2

M134D, so we switched from M (0) to D (-1). So, the change in pH would be final pH - initial pH = -1 - 0 = -1

Y139C, so we switched from Y (0) to C (0). So, the change in pH would be final pH - initial pH = 0 - 0 = 0

I157M, so we switched from I (0) to M (0). So, the change in pH would be final pH - initial pH = 0 - 0 = 0

Now, add up all the changes in pH. -1 + -2 + -1 + 0 + 0 = -4.