Let’s consider histidine as a free amino acid in aqueous solution. a) Draw the most likely structure of histidine under biochemical standard state conditions. b) Given that free histidine has the following three pKa values, assign each to its corresponding acidic hydrogen or conjugate base in your structure from part a). pKa1 = 1.7; pKa2 = 6.2; and pKa3 = 9.1 c) For each pKa, give the corresponding expression for the equilibrium constant. It helps to write out the chemical equation for each. d) Create a speciation diagram for histidine by plotting Xi vs pH from pH = 4 to pH = 8 where Xi is the mole fraction of the two histidine species involved in the K2 equilibrium in part c).
Let’s consider histidine as a free amino acid in aqueous solution.
a) Draw the most likely structure of histidine under biochemical standard state conditions.
b) Given that free histidine has the following three pKa values, assign each to its corresponding acidic hydrogen or conjugate base in your structure from part a).
pKa1 = 1.7; pKa2 = 6.2; and pKa3 = 9.1
c) For each pKa, give the corresponding expression for the equilibrium constant. It helps to write out the chemical equation for each.
d) Create a
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