. Author manuscript; available in PMC: 2010 Jul 3.

Published in final edited form as: J Mol Biol. 2009 May 6;390(1):124–134. doi: 10.1016/j.jmb.2009.04.075

Table 4.

Kinetic parameters for denatured state loop breakage and loop formation at 25 °C in 3 M gdnHCl for variants of iso-1-cytochrome c

Variant	Loop Breakage^a		Loop Formation^a,^b

	k_obs, s⁻¹ (pH 3.50)	k_obs, s⁻¹ (pH 3.00)	k_f, s⁻¹

His_Ala Variants^c
NH5A	100.5 ± 1.0	93.0 ± 0.2	8910 ± 830
Gly1	91.6 ± 1.8	83.1 ± 1.9	9360 ± 470
Gly2	87.4 ± 0.9	76.8 ± 0.7	9900 ± 1000
Gly3	92.1 ± 1.3	81.6 ± 1.0	9740 ± 460
Gly4v3	94.9 ± 3.0	87.2 ± 1.0	10670 ± 470
His_Gly Variants^d
Gly1v2	110.3 ± 3.6	101.8 ± 2.3	9080 ± 540
Gly3v2	109.5 ± 3.9	96.7 ± 3.1	9790 ± 1370
Gly4v2	114.0 ± 2.5	100.8 ± 3.8	10860 ± 480
Gly4	116.2 ± 2.2	107.0 ± 1.8	11230 ± 500
Gly5	122.0 ± 2.3	111.4 ± 1.3	11300 ± 480

The errors reported for k_obs are the standard deviations of the mean and those for k_f are from standard propagation of errors.

Loop closure rate constants are beyond the limitation of our SX-20 stopped-flow apparatus. Thus, these values were extracted using pK_loop obtained as described in the text. k_f was calculated as k_f = k_b× K_loop = k_b× 10^−pK_loop, using k_obs for loop breakage at pH 3.00 for k_b.

Variants where the amino acid on the C-terminal side of the His which forms the loop with the heme is an alanine.

Variants where the amino acid on the C-terminal side of the His which forms the loop with the heme is a glycine.