Question

Describe the behavior of a mixture of glutamic acid, arginine, and valine on paper electrophoresis at \(\mathrm{pH} 6.0\).

Short answer

Answer: At pH 6.0, glutamic acid, arginine, and valine behave differently on paper electrophoresis due to their varying charges. Glutamic acid will migrate towards the anode (positive electrode) as it is negatively charged at this pH, while arginine will migrate towards the cathode (negative electrode) as it is positively charged. Valine will have minimal migration due to its neutral charge at pH 6.0.

Step-by-step solution

Calculate the charge of each amino acid at pH 6.0

To predict the behavior of the amino acids on paper electrophoresis at pH 6.0, we need to determine the charge of each amino acid at this pH. The charges of amino acids depend on their side-chain functional group and the ionizable groups in the molecule (carboxyl and amino groups). Amino acids can be classified into acidic, basic, or neutral based on their side-chain groups. For glutamic acid, arginine, and valine their pKa values are as follows: Glutamic acid (Glu): COOH: pKa = 2.19 NH3+: pKa = 9.67 R-group (COOH): pKa = 4.25 Arginine (Arg): COOH: pKa = 2.17 NH3+: pKa = 9.04 R-group (NH3+): pKa = 12.48 Valine (Val): COOH: pKa = 2.29 NH3+: pKa = 9.72 Now, compare the pH of the solution (6.0) with the pKa values of each amino acid to determine their charges at this pH.

Determine the isoelectric points (pIs) of the amino acids

Isoelectric point (pI) is the pH at which the net charge of an amino acid is zero. The pIs of the amino acids are calculated using the average of the two pKa values that involve the amino acid's neutral form (zwitterion). The pIs for glutamic acid, arginine, and valine are: Glutamic acid (Glu): pI = (2.19 + 4.25) / 2 = 3.22 Arginine (Arg): pI = (9.04 + 12.48) / 2 = 10.76 Valine (Val): pI = (2.29 + 9.72) / 2 = 6.01

Analyze the behavior of amino acids on paper electrophoresis at pH 6.0

Paper electrophoresis separates molecules based on their charge and size. At pH 6.0, calculate the charges of the amino acids based on their pKa values: Glutamic acid (Glu): -1 (negatively charged) Arginine (Arg): +1 (positively charged) Valine (Val): 0 (neutral) During electrophoresis, the amino acids will migrate according to their charge: - Glutamic acid, which is negatively charged at pH 6.0, will migrate towards the positive electrode (anode). - Arginine, which is positively charged at pH 6.0, will migrate towards the negative electrode (cathode). - Valine will have a neutral charge at pH 6.0 and will migrate at a slower rate, as it will be primarily affected by its size and shape rather than its charge. In conclusion, at pH 6.0, glutamic acid, arginine, and valine will behave differently on paper electrophoresis due to their varying charges. Glutamic acid will migrate towards the anode, arginine will migrate towards the cathode, and valine will have minimal migration due to its neutral charge.