N-term
pKa = 8.23+3.6 / -0.27

CHC-6.6 /OOHCCCH2CHNHC

HNC

CH2+1.1+2.6 / -0.92 (ε1)

HC

NH2+0.1/ -0.01++4.2+0.3 / -0.01
0.0 /H C
0.00 30.0 C
OH
N+0.4 /
0.0 , +0.11

CH2C

CH

N
H

-0.3 / -0.33 (δ2)

C+0.1/+0.02+0.2 /H3C+0.1+0.4 /+0.6H
N

C

CH2

CH +3.3 / -0.28

HCCH -0.1 / -0.17

CH+0.1 / -0.08

CH
N+0.4Arg
pKa = 13.9
H2 NH2N

C+0.1 /NH2H
N

0.0 /
H C
0.00 3C0.0CH2P+0.1 /+0.3 / -0.04

OCH2CCH

NHCO

HN

C

CH2+0.50.0
NH2+0.0 / -0.01

ON+2.8 / H+0.64

CH-1.2 / -0.11

O

OO

O+1.0OH

0.0 / -0.01

CH -2.4 / -0.25-0.4 / -0.05+0.3/-0.06 H3C+6.1 /+0.78

NHPO

CHO+4.0OH

C
HC+0.8CH

HC+1.8 / -0.25
CPO+4.3+1.1 / -0.17
C+0.4 / -0.04

O-OHCH2+0.2/ 0.0 , 0.04

+5.0 / -0.24

pTyr
pKa = 5.96

pThr
pKa = 6.30

CH2 +1.0 /O

NH2+0.1/ -0.01

O+0.7 /O+0.2 / -0.07+0.50

C+2.1 / -0.28-0.1 / 0.0O+3.9O

C+1.9+0.4 / -0.08 CH
2O-O-CH2NH3++0.3 / -0.06

CH2 +0.5 / -0.19

CHCO

HN+0.1+5.9 / NH+0.4 /NH

CH2+0.1/ +0.01

O

NH2+C +4.0CH2 +0.9 /CH~-7.5 /O

CH2+0.6 /+1.0 / -0.40 CH2pSer
pKa = 5.96+22 /+0.0 /+0.01 , -0.01+3.6 /0.0+0.6 /C+0.0 / -0.01

CC+0.0 / +0.02

OCH2O

CH2/ 0.0 , -0.11

HCNHHNO

NH2C

CH2NH2/ 0.00

+0.1 / -0.10

Lys
pKa = 10.34

O+0.6+0.1

C

CH2SH+0.1 / H C
3+0.01
C+0.1

OH-6.7COHNO-0.4+1.6 / ~-0.2+10.4

CHNH+0.1+0.1/ -0.06

O+1.8 / ~-0.2C

CH2+1.50.0Tyr
pKa = 9.76

CCH2+0.1/ +0.02+1.7 / -0.09

OHNOHCH2O

CyspKa = 8.49

+2.4 / -0.17

CC+1.5 / -0.06+0.0 / +0.01

O+0.5 /CH2+4.1+1.0 / +0.12+8 /CHO-0.1 / -0.01

HN

0.0 /H C+0.01 3
C
0.0+1.4 / -0.17

NH+56 / HN

+0.2 / 0.00

+0.4-0.20

HispKa = 6.45

O+3.5 / -0.22 CH2OO+1.5 / -0.17+2.3 / -0.21

CH3GlupKa = 4.34

+0.1 / -0.03

CH2O

0.0 / +0.01

O+8.5+3.0 / -0.23+0.3 / +0.02
HN+3.2+1.3 / -0.09
O-0.70 CCHOH+0.4 / H C
NC3+3.4-0.02
H+5.2 / -0.41 O

NH2O

Asp
pKa = 3.86+0.1 /+0.01 H3CC
0.0+1.0 / -0.59

CH3+H3N

C-termpKa = 3.55

CHC-0.03 / -0.02 CH2+0.2 / N
H+0.02CH

0.0 / -0.02
C 0.0OpH-Dependent random coil 1H, 13C, and 15N chemical shifts of
the ionizable amino acids: a guide for protein pKa measurements
Gerald Platzer, Mark Okon, and Lawrence P. McIntosh
Department of Biochemistry and Molecular Biology, Department of Chemistry, and Michael Smith
Laboratories, University of British Columbia, Vancouver BC, V6T 1Z3, Canada

A summary of the pH-dependent chemical shift changes upon deprotonation of the ionizable amino acidfunctional groups within the context of the blocked acetyl-Gly-X-Gly-amide (X = Asp, Glu, His, Cys,Tyr, or Lys) tripeptides. Alanine amide and N-acetyl alanine are models of the N- and C-termini,respectively. The atoms and Δδ values (ppm; negative is upfield) are colored as: acidic protons, red;oxygens and non-labile protons, black within the named residue and grey in flanking blocked glycines;
carbons, green; nitrogens, blue; sulfurs, yellow; and phosphates, magenta. Results for 13C6/15N4-Larginine are due to deprotonation of the guanidinium moiety in the context of deprontonated α-amino(pKa 9.15) and α-carboxyl groups. Values for the neutral forms of the Gly-His-Gly tripeptide andarginine are tautomer averaged.
The tripeptides and alanine derivatives were initially in 50 mM NaCl with 5% D2O (D = 2H). DSS (4,4dimethyl-4-silapentane-1-sulfonic acid; 1 mM) was included as a pH-independent internal reference. For
the cysteine tripeptide, 10 mM TCEP (tris(2-carboxyethyl)phosphine) was also present as a reductant.
The 13C6/15N4-L-arginine was initially 10 or 100 mM in 50 mM NaCl with 1 mM DSS and 5% D2O.
Spectra were recorded at 25 oC.
The data are from Platzer et al. J Biomol NMR 60:109-129 (2014), or in the case of the phosphoaminoacid peptides (second ionization step for acetyl-Gly-Gly-X-Gly-Gly-amide, X=pSer, pThr, or pTyr),from Bienkiewicz & Lumb, J Biomol NMR 15:203-206 (1999).