Subangstrom crystallography reveals that short ionic hydrogen bonds, and not a His-Asp low-barrier hydrogen bond, stabilize the transition state in serine protease catalysis.
Fuhrmann, Cynthia N; Daugherty, Matthew D; Agard, David A; Journal of the American Chemical Society 128 (2006) 9086–9102; doi:10.1021/ja057721o

data_4101246
_publ_section_title
;
 Subangstrom crystallography reveals that short ionic hydrogen bonds,
 and not a His-Asp low-barrier hydrogen bond, stabilize the transition
 state in serine protease catalysis.
;
_journal_issue                   28
_journal_name_full               'Journal of the American Chemical Society'
_journal_page_first              9086
_journal_page_last               9102
_journal_paper_doi               10.1021/ja057721o
_journal_volume                  128
_journal_year                    2006
_chemical_formula_sum            'C846 H1919 N262 O491 S8.83'
_chemical_formula_weight         23904.63
_chemical_name_systematic
; 
 ? 
;
_space_group_IT_number           154
_symmetry_space_group_name_Hall  'P 32 2"'
_symmetry_space_group_name_H-M   'P 32 2 1'
_atom_sites_solution_hydrogens   geom
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_creation_method           SHELXL-97
_cell_angle_alpha                90.00
_cell_angle_beta                 90.00
_cell_angle_gamma                120.00
_cell_formula_units_Z            6
_cell_length_a                   65.68(7)
_cell_length_b                   65.68(7)
_cell_length_c                   79.46(8)
_cell_measurement_temperature    98(2)
_cell_volume                     296844(515)
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 1997)'
_computing_structure_solution
;
;
_diffrn_ambient_temperature      98(2)
_diffrn_measured_fraction_theta_full 0.979
_diffrn_measured_fraction_theta_max 0.979
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_diffrn_reflns_av_R_equivalents  0.0000
_diffrn_reflns_av_sigmaI/netI    0.0258
_diffrn_reflns_limit_h_max       80
_diffrn_reflns_limit_h_min       0
_diffrn_reflns_limit_k_max       0
_diffrn_reflns_limit_k_min       -40
_diffrn_reflns_limit_l_max       88
_diffrn_reflns_limit_l_min       -89
_diffrn_reflns_number            189104
_diffrn_reflns_theta_full        28.60
_diffrn_reflns_theta_max         28.60
_diffrn_reflns_theta_min         1.16
_exptl_absorpt_coefficient_mu    0.074
_exptl_crystal_density_diffrn    0.802
_exptl_crystal_density_method    'not measured'
_exptl_crystal_F_000             77390
_refine_diff_density_max         0.498
_refine_diff_density_min         -0.373
_refine_diff_density_rms         0.065
_refine_ls_abs_structure_details 'Flack H D (1983), Acta Cryst. A39, 876-881'
_refine_ls_abs_structure_Flack   0(10)
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.691
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           fullcycle
_refine_ls_number_parameters     20529
_refine_ls_number_reflns         189104
_refine_ls_number_restraints     24947
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_refine_ls_R_factor_all          0.0817
_refine_ls_R_factor_gt           0.0728
_refine_ls_shift/su_max          0.000
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.1000P)^2^+0.0000P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
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