. Author manuscript; available in PMC: 2017 Jan 12.

Published in final edited form as: Biochemistry. 2015 Dec 23;55(1):157–166. doi: 10.1021/acs.biochem.5b01241

Table 1. Transition States, Barrier Crossing Times and Activation Free Energies for light and heavy DHFRs^a.

		d_DA (Å)
DHFR	T (K)	from T-d KIEs^b	from TPS^a	d_DH - d_HA (Å)^a	barrier-crossing time (fs)^a	ΔG^‡ (kcal/mol)^c
light	280	3.06 ± 0.08	2.82 ± 0.08	0.21 ± 0.07	6 ± 3	10 ± 2
	300		2.72 ± 0.07	0.19 ± 0.07	8 ± 5	11 ± 2
heavy	280	3.36 ± 0.01	2.77 ± 0.08	0.11 ± 0.04	6 ± 3	10 ± 1
	300		2.82 ± 0.06	0.21 ± 0.12	6 ± 2	11 ± 2

Parameters predicted from TPS simulations. Additional parameters are listed in Table S1 in Supporting Information. Experimentally measured activation free energies (ΔG^‡) are also independent of enzyme mass.

Data from ref 5.

Parameters determined by pre-steady-state kinetic experiments.

Table 1. Transition States, Barrier Crossing Times and Activation Free Energies for light and heavy DHFRsa.

Table 1. Transition States, Barrier Crossing Times and Activation Free Energies for light and heavy DHFRs^a.