Titration Curve and pl 12 NH2ch2coo 10 pKa2=9.6 pH>9.6 H 8 6 pl=60 NH3 CH2cOo 2.3≤pH<9.6 pKa1=2.3 H3CH2coo pH<2.3 00.51 52 加入OH的当量
Titration Curve and pI
Calculation of pI (1) HaN-C-cooH pKi NHa-c-coo pK2 NHa-c-coo CH CH CH low pH high pH 电荷 11e 编号 Ⅲ O pKa=2.34 CH3CHCOH NH alanine pKa=9.69 2.34+9.6912.03 p =6.02
Calculation of pI (1) H C COOH NH 3 H C CO O NH 2 H C COO p K1 p K2 lo w pH pI high pH 电荷 1 1 1 1 编号 Ⅱ Ⅰ Ⅲ H 3 N CH 3 CH 3 CH 3
Calculation of pl (2) NH3CH2 CH2 CH2CH2 CHCOOH pKi NH3CH2 CH2 CH2 CH2 CHCOO 20 10 Nh 2 NH3CH2 CH2 CH2 CH2 CHCOO NH2 CH2 CH2 CH2 CH2 CHCOO NH 11 pKa=2. 18 十 H3NCH2 CH2CH2 CH, CHCOH pKa=10.79 N pKa=8.95 sIne 8.95+10.7919.74 2=.87
Calculation of pI (2) N + H 3CH 2CH 2CH 2CH 2CHCOO H NH 3 p K1 N + H 3CH 2CH 2CH 2CH 2CHCO O- NH 3 p K2 N + H 3CH 2CH 2CH 2CH 2CHCO O- NH 2 p KNH2 NH 2CH 2CH 2CH 2CH 2CHCO O- NH 2 2 2 1 1 1 1
Calculation of pI 3) pK1 HOOCCH2 CH2 CHCOOH HOOCCH2CH2CHCO0 16 10 NH 1G4h3 COOH OOCCH2 CH2 CHCOO oocCHbCHbCHCOO NH NH 2 261 2 pKa=2.19 HOCCH, CH,CHCOH p a≈4 25 NH glutamic acid >pKa=9.67 2.19+4.256.44 2 2=3.22
Calculation of pI (3) HOOCCH 2CH 2CHCOOH NH 3 p K1 HOOCCH 2CH 2CHCOONH 3 p KCO O H -OOCCH 2CH 2CHCO O- NH 3 p K2 - OOCCH 2CH 2CHCO O- NH 2 2 1 2 1 1 1
(2)Isoelectric Point ④纸电泳( aper electrophoresis cathode anode tNH H2NCNHCH, CH, CH,CHCO CHCHCO OCCH CHCO NH NH arginine alanine aspartate pl=10.76 pl=6.02 pl=298 p<pl,样品带正电荷,样品点向阴极移动 p>pl,样品带负电荷,样品点向阳极移动 p=p样品不带电荷,样品点不移动
(2) Isoelectric Point ④纸电泳 (Paper electrophoresis) pH < pI, 样品带正电荷，样品点向阴极移动 pH > pI, 样品带负电荷，样品点向阳极移动 pH = pI, 样品不带电荷，样品点不移动