Destabilization of the 310-Helix in Peptides Based on Cα-Tetrasubstituted α-Amino Acids by Main-Chain to Side-Chain Hydrogen Bonds
Wojciech M. Wolf; Marcin Stasiak; Miroslav T. Leplawy; Alberto Bianco; Fernando Formaggio; Marco Crisma; Claudio Toniolo; Journal of the American Chemical Society 120 (1998) 11558–11566; doi:10.1021/ja982194c

data_4116886
_publ_section_title
;
 Destabilization of the 310-Helix in Peptides Based on
 C\a-Tetrasubstituted \a-Amino Acids by Main-Chain to Side-Chain Hydrogen
 Bonds
;
_journal_name_full               'Journal of the American Chemical Society'
_journal_page_first              11558
_journal_page_last               11566
_journal_paper_doi               10.1021/ja982194c
_journal_volume                  120
_journal_year                    1998
_chemical_formula_sum            'C20 H34 N2 O9'
_chemical_formula_weight         446.49
_chemical_name_common            Boc-[Hms(Ipr)]2-OMe
_space_group_IT_number           14
_symmetry_cell_setting           monoclinic
_symmetry_space_group_name_Hall  '-P 2yab'
_symmetry_space_group_name_H-M   'P 1 21/a 1'
_atom_sites_solution_hydrogens   geom
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_creation_method           SHELXL
_cell_angle_alpha                90.00
_cell_angle_beta                 90.3(1)
_cell_angle_gamma                90.00
_cell_formula_units_Z            4
_cell_length_a                   18.180(3)
_cell_length_b                   11.754(2)
_cell_length_c                   11.214(2)
_cell_measurement_reflns_used    24
_cell_measurement_temperature    293(2)
_cell_measurement_theta_max      12
_cell_measurement_theta_min      7
_cell_volume                     2396.3(7)
_computing_structure_refinement  'SHELXL-93 (Sheldrick, 1993)'
_computing_structure_solution    'SHELXS-86 (Sheldrick, 1985)'
_diffrn_ambient_temperature      293(2)
_diffrn_measurement_device       'Philips PW1100 diffractometer'
_diffrn_measurement_method       '\q-2\q scan'
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_source         'fine-focus sealed tube'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0140
_diffrn_reflns_av_sigmaI/netI    0.0262
_diffrn_reflns_limit_h_max       24
_diffrn_reflns_limit_h_min       -23
_diffrn_reflns_limit_k_max       15
_diffrn_reflns_limit_k_min       0
_diffrn_reflns_limit_l_max       14
_diffrn_reflns_limit_l_min       0
_diffrn_reflns_number            6069
_diffrn_reflns_theta_max         28.01
_diffrn_reflns_theta_min         2.06
_diffrn_standards_interval_count 100
_diffrn_standards_number         3
_exptl_absorpt_coefficient_mu    0.097
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    1.238
_exptl_crystal_description       prism
_exptl_crystal_F_000             960
_exptl_crystal_size_max          0.50
_exptl_crystal_size_mid          0.50
_exptl_crystal_size_min          0.40
_refine_diff_density_max         0.452
_refine_diff_density_min         -0.367
_refine_diff_density_rms         0.040
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_all   1.064
_refine_ls_goodness_of_fit_obs   1.199
_refine_ls_hydrogen_treatment    riding
_refine_ls_matrix_type           full
_refine_ls_number_parameters     307
_refine_ls_number_reflns         5783
_refine_ls_number_restraints     4
_refine_ls_restrained_S_all      1.185
_refine_ls_restrained_S_obs      1.200
_refine_ls_R_factor_all          0.0965
_refine_ls_R_factor_obs          0.0459
_refine_ls_shift/esd_max         -0.003
_refine_ls_shift/esd_mean        0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'w=1/[\s^2^(Fo^2^)+(0.0846P)^2^+0.0709P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_all         0.1669
_refine_ls_wR_factor_obs         0.1358
_reflns_number_observed          3837
_reflns_number_total             5789
_reflns_observed_criterion       >2sigma(I)
_cod_data_source_file            ja982194c_1.cif
_cod_data_source_block           (dipeptide)
_cod_database_code               4116886