Chapter 5 - Proteins: Primary Structure - Exercises - Page 127: 7

a) At ph 6 ,pka of his is 6.09,ie His side chain is 50% charged(+0.50). Similarly Arg(+1),and Leu is (0). The C-terminal Pka is 2.2 and so it is -1 at ph 6. The N-terminal Pka is 9.4 and so it is +1 at ph 6. Carboxy methy matrix is the most commonly used cation exchanger. The molecules with posive charge will stick to the negatively charged coloum first.so the order will be Leu(0)-His(+0.5)-Arg(+1) b) At Ph 8,Glu(-1), Val(0),Lys(+1). The C-terminal Pka is 2.2 so it is -1 at ph 8 The N-terminal Pka is 9.4 so it is +1 at ph 8. Diethylaminoethyl is an anionic coloumn ,so the negatively charged molecules will stick to the anion exchanger and come off later. So the order would be LYS(+1)-VAI(0) Glu(-1).

a) At ph 6 ,pka of his is 6.09,ie His side chain is 50% charged(+0.50). Similarly Arg(+1),and Leu is (0). The C-terminal Pka is 2.2 and so it is -1 at ph 6. The N-terminal Pka is 9.4 and so it is +1 at ph 6. Carboxy methy matrix is the most commonly used cation exchanger. The molecules with posive charge will stick to the negatively charged coloum first.so the order will be Leu(0)-His(+0.5)-Arg(+1) b) At Ph 8,Glu(-1), Val(0),Lys(+1). The C-terminal Pka is 2.2 so it is -1 at ph 8 The N-terminal Pka is 9.4 so it is +1 at ph 8. Diethylaminoethyl is an anionic coloumn ,so the negatively charged molecules will stick to the anion exchanger and come off later. So the order would be LYS(+1)-VAI(0) Glu(-1).