Table 2.

Effect of amino acid side chains on the HX rates of neighboring peptides, given as Log₁₀k_ex(X)-Log₁₀k_ex(Ala). The modified L Base reference rate factors for Gly and deprotonated Asn and Glu are shown in bold. The other values are as in Bai et al. (9). L refers to the effect of that side chain on the exchange rate of the amide to its immediate left, toward the N-terminus. R refers to the effect on the amide toward the C-terminus, separated by an intervening carbonyl.

	Acid		Base
Side chain	L	R	L	R
Ala	0.00	0.00	0.00	0.00
Arg	−0.59	−0.32	0.08	0.22
Asn	−0.58	−0.13	0.49	0.32
Asp(COO−)	0.90	0.58	0.10	−0.18
Asp(COOH)	−0.90	−0.12	0.69	0.60
Cys	−0.54	−0.46	0.62	0.55
Cys2	−0.74	−0.58	0.55	0.46
GlY	−0.22	0.22	−0.03	0.17
Gln	−0.47	−0.27	0.06	0.20
Glu(COO−)	−0.90	0.31	−0.11	−0.15
Glu(COOH)	−0.60	−0.27	0.24	0.39
His			−0.10	0.14
His+	−0.80	−0.51	0.80	0.83
Ile	−0.91	−0.59	−0.73	−0.23
Leu	−0.57	−0.13	−0.58	−0.21
Lys	−0.56	−0.29	−0.04	0.12
Met	−0.64	−0.28	−0.01	0.11
Phe	−0.52	−0.43	−0.24	0.06
Pro(trans)		−0.19		−0.24
Pro(cis)		−0.85		0.60
Ser	−0.44	−0.39	0.37	0.30
Thr	−0.79	−0.47	−0.07	0.20
Trp	−0.40	−0.44	−0.41	−0.11
Tyr	−0.41	−0.37	−0.27	0.05
Val	−0.74	−0.30	−0.70	−0.14
N-term (NH3+)		−1.32		1.62
C-term (COO−)	0.96		−1.80
C-term (COOH)	0.05