Table 1.

Second-order rate constant for backbone amides varies over several orders of magnitude, depending on the environment. This value is a maxima estimate based on studies with cyclic dipeptides.

Residue	K2 M−1 s−1	Residue	K2 M−1 s−1
Met	3.8 × 107	Lys	5.0 × 103
Cys	3.0 × 107	Tyr	44
Cistine	1.6 × 105	Arg	26
His	1.0 × 105	Backbone amides	<10
α-amino	1.0 × 105	Asn	0.03
Trp	1.1 × 104	Gln	0.03