Please use the attached pKa table to solve this problem Do n

Please use the attached pKa table to solve this problem. Do not use any other pKa table except what is included here. What is the isoelectric point of the following tetrapeptide that contains the amino acids represented by the single letters \'TLIK\", such that Tis at the amino-terminal end of the peptide and Kis at the carboy-terminal end. (-COOH) Amino Acid pk, Glycine 9.600 9.69 2.32 9.62 Leucine Isoleucine 9.60 9.15 2.63 10.43 9.21 2.28 Phenylalanine 9.13 2.83 8.80 Asparagine 2.17 Glutamine 9.13 10.60 Proline 1.99 10.78 9.17 6.000 Aspartic acid 2.09 9.82 2.19 Glutamic acid 9.67 4.25 2.20 9.11 10.07 8.95 10.79 2.17 9.04. O A. 9.5 O B. 10.00 O C. 10.07 E. 10.61

Solution

in the peptide \'TLIK\' \'T\' (threonine) is at the amino terminal end. therefore, its amino group is free. its carboxyl group is attached to amino group of \'L\' (leucine). leucine has no functional group in its side chain. its carboxyl group is attached to amino group of \'K\' (Lysine). the carboxyl group of \'K\' is free.

therefore, amino group of \'T\' and carboxyl group of \'K\' are free. the amino and carboxyl groups of \'L\' and \'I\' are not free, and they have no functional groups in their side chains.

pKa value of amino group of \'T\' = 10.43

pKa value of \'K\' = 10.79

average of the above the above two values = 10.61

(NOTE: since only the amino group of \'K\' is freely available, we should consider the pKa of only COOH of \'K\' i.e, 2.18. therefore, pI would be average of 10.43 and 2.18, i.e, 6.3. But since this answer is not given in the options, I did it in the other way. However, I think this is the correct way of solving this question)