Table 1 EXAFS simulation parameters of lyophilized HYDA1 proteinsa.

From: Lyophilization protects [FeFe]-hydrogenases against O2-induced H-cluster degradation

  

N [per Fe ion]/R [Å]/2σ2 × 103 [Å2]

RF [%]

HYDA1:

 

Fe-C/O

Fe-S

Fe-Fe, [2FeH]

Fe-Fe, [4FeH]

Fe…O/N

 

[4FeH]

−O2

–

4/2.28/7

–

3/2.73/10

–

9.0

 

+O2

–

4/2.28/7

–

3/2.73/10

–

12.2

[6FeH]

−O2

1/1.91/5#

3.5/2.27/10

0.5/2.55/2#

2/2.72/7

1/3.00/5#

12.5

 

+O2

1/1.87/5# 0.82*/1.86/5#

3.5/2.26/9 3.65*/2.26/10&

0.5/2.58/2# 0.5/2.57/2#

2/2.71/10 1.87*/2.71/7&

1/3.05/5# 1/3.07/5#

14.4 14.7

 

+O2 +H2O

3.07*/2.04/5#

1.73*/2.29/10&

0.05*/2.55/2#

0.39*/2.71/7&

0.34*/3.18/5#

13.8

  1. aN, coordination number; R, interatomic distance; 2σ2, Debye-Waller parameter; RF, fit error sum calculated for reduced distances of 1–3 Å25. Data correspond to EXAFS spectra in Fig. 4b. Fit restraints: N-values were fixed to the given numbers in the fits representing the expected coordination numbers for the [4Fe4S] cluster in HYDA1[4FeH] or the approximate N-values for a complete H-cluster in HYDA1[6FeH]21,28, *except for N-values that were allowed to vary in the fits; &the same 2σ2-values were used for respective fits of spectra plus or minus O2; #2σ2 values that were fixed in the simulations. For [6FeH] +O2, the fit result for unrestricted N-values (*) emphasizes that the Fe-CO/N and Fe-S bonds and the Fe-Fe interactions in the H-cluster are fully preserved in the presence of O2.
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