Table 1. Equilibrium rate constants of BMAA with α-carbamate and β-carbamate adducts using EXSY experiments.

	BMAA:HCO3- = 1:10		BMAA:HCO3- = 1:20		BMAA:HCO3- = 1:30
Kinetic Parameters (i = α or β)	α-carbamate	β-carbamate	α-carbamate	β-carbamate	α-carbamate	β-carbamate
$k_{1i}^{**}\left(s^{-1}\right)$	0.17 ± 0.03	0.6 ± 0.05	0.45 ± 0.02	1.13 ± 0.03	0.85 ± 0.03	1.66 ± 0.04
$t_{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.,1i}\left(s\right)$	4.18 ± 0.99	1.17 ± 0.1	1.53 ± 0.07	0.61 ± 0.01	0.82 ± 0.07	0.42 ± 0.08
$k_{1i}^{*}\left(M^{-1}{s}^{-1}\right)$	1.73 ± 0.35	5.97 ± 0.49	2.27 ± 0.1	5.65 ± 0.13	2.83 ± 0.1	5.53 ± 0.01
k1(M-1s-1)	0.04 ± 0.01	0.15 ± 0.01	0.06 ± 0.01	0.14 ± 0.02	0.07 ± 0.01	0.14 ± 0.01
$k_{2i}^{*}\left(s^{-1}\right)$	0.23 ± 0.02	1.89 ± 0.03	0.17 ± 0.02	1.75 ± 0.02	0.14 ± 0.05	1.25 ± 0.15
$t_{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.,2i}\left(s\right)$	3.08 ± 0.34	0.37 ± 0.01	4.13 ± 0.49	0.4 ± 0.05	5.02 ± 0.14	0.55 ± 0.11
k2i(M−1s−1) × 10−8	5.72 ± 0.62	47.59 ± 0.65	4.27 ± 0.49	43.91 ± 0.52	3.47 ± 0.2	31.5 ± 0.12
$K_i^{*}\left(M^{-1}\right)$	7.7 ± 1.77	3.15 ± 0.26	13.52 ± 1.71	3.23 ± 0.09	20.51 ± 0.58	4.41 ± 0.2
Ki × 106	7.6 ± 1.75	3.11 ± 0.26	13.35 ± 1.69	3.19 ± 0.08	20.25 ± 0.58	4.36 ± 0.09
$\Delta G_i^{*}\left(\raisebox{1ex}{$kJ$}\!\left/ \!\raisebox{-1ex}{$mol$}\right.\right)$	-5.14 ± 1.18	-2.89 ± 0.24	-6.56 ± 0.83	-2.96 ± 0.08	-7.61 ± 0.22	-3.74 ± 0.17

For each i = α (α-carbamate) and i = β (β-carbamate) the rate constants $k_{1i}^{**}$ and $k_{2i}^{*}$ were determined by proton exchange NMR spectroscopy (EXSY). Reaction half-lives were determined by assuming a first order kinetics ($t_{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.,i}=\raisebox{1ex}{$\text{ln}\left(2\right)$}\!\left/ \!\raisebox{-1ex}{$k_i$}\right.$). The equilibrium constants $K_i^{*}$ were then calculated using $k_{1i}^{*},k_{1i}$ and k_2i along with the estimates obtained by propagating the measured standard error in the NMR spectra (materials and methods). The Gibbs free energy was then estimated using $\Delta G_i^{*}=-RT\text{ln}\left(K\right)$. The experiments were performed in a total volume of 600 μL containing 5 mM BMAA and varying concentration of NaHCO₃ (100 mM, 200 mM and 300 mM). The sample pD was at 7.6 and the experiments were performed at 303 K.