Table 2.

Computed Primary (1 degree) and Secondary (2 degree) Kinetic Isotope Effects, and Computed and Experimental Total Deuterium Isotope Effects for the Proton Transfer from Nitroethane to Asp402 in NAO and to Acetate Ion in Water

Primary KIE	${\mathit{k}}_{\mathbf{H}}^{\mathbf{H}}/{\mathit{k}}_{\mathbf{D}}^{\mathbf{H}}$	${\mathit{k}}_{\mathbf{H}}^{\mathbf{H}}/{\mathit{k}}_{\mathbf{T}}^{\mathbf{H}}$	${\mathit{k}}_{\mathbf{D}}^{\mathbf{D}}/{\mathit{k}}_{\mathbf{T}}^{\mathbf{D}}$
H2O	6.63 ± 0.31	13.0 ± 1.0	2.17 ± 0.04
NAO	8.36 ± 0.58	18.1 ± 2.4	2.38 ± 0.05
Secondary KIE	${\mathit{k}}_{\mathbf{H}}^{\mathbf{H}}/{\mathit{k}}_{\mathbf{H}}^{\mathbf{D}}$	${\mathit{k}}_{\mathbf{H}}^{\mathbf{H}}/{\mathit{k}}_{\mathbf{H}}^{\mathbf{T}}$	${\mathit{k}}_{\mathbf{D}}^{\mathbf{D}}/{\mathit{k}}_{\mathbf{D}}^{\mathbf{T}}$
H2O	1.340 ± 0.132	1.375 ± 0.183	1.096 ± 0.048
NAO	1.213 ± 0.150	1.229 ± 0.209	1.050 ± 0.025
Total ${\mathit{k}}_{\mathbf{H}}^{\mathbf{H}}/{\mathit{k}}_{\mathbf{D}}^{\mathbf{D}}$	Calc.	Expt.
H2O	8.3 ± 1.1	7.8 ± 0.1
NAO	10.1 ± 1.4	9.2 ± 0.4

Subscripts and superscripts are used to specify the rate constant for isotope substitutions at the primary and secondary position, respectively.