The structure of nanotubes formed by diphenylalanine, the core recognition motif of Alzheimer's beta-amyloid polypeptide
C.H.Gorbitz; Chemical Communications  (2006) –; doi:10.1039/b603080g

data_7101186
_publ_section_title
;
The structure of nanotubes formed by diphenylalanine, the core recognition
motif of Alzheimer's beta-amyloid polypeptide
;
_journal_issue                   22
_journal_name_full               'Chemical Communications'
_journal_paper_doi               10.1039/b603080g
_journal_year                    2006
_chemical_absolute_configuration rm
_chemical_formula_moiety         'C20 H21 N3 O3, 0.75H2 O'
_chemical_formula_sum            'C20 H22.5 N3 O3.75'
_chemical_formula_weight         364.91
_chemical_name_common            'L-phenylalanyl-L-tryptophane 0.75 hydrate'
_chemical_name_systematic
;
L-phenylalanyl-L-tryptophane 0.75 hydrate
;
_space_group_IT_number           19
_symmetry_cell_setting           orthorhombic
_symmetry_space_group_name_Hall  'P 2ac 2ab'
_symmetry_space_group_name_H-M   'P 21 21 21'
_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                90.00
_cell_formula_units_Z            16
_cell_length_a                   5.6207(6)
_cell_length_b                   35.556(4)
_cell_length_c                   35.835(4)
_cell_measurement_reflns_used    1981
_cell_measurement_temperature    105(2)
_cell_measurement_theta_max      20.82
_cell_measurement_theta_min      0.81
_cell_volume                     7161.5(15)
_computing_cell_refinement       'SAINT (Bruker, 2001)'
_computing_data_collection       'SMART (Bruker, 1998)'
_computing_data_reduction        'SAINT (Bruker, 2001)'
_computing_molecular_graphics    'SHELXTL (Bruker, 2000)'
_computing_publication_material  'SHELXTL (Bruker, 2000)'
_computing_structure_refinement  'SHELXTL (Bruker, 2000)'
_computing_structure_solution    'SHELXTL (Bruker, 2000)'
_diffrn_ambient_temperature      105(2)
_diffrn_detector_area_resol_mean 8.3
_diffrn_measured_fraction_theta_full 0.979
_diffrn_measured_fraction_theta_max 0.979
_diffrn_measurement_device_type  'Siemens SMART CCD diffractometer'
_diffrn_measurement_method
;
Three sets of frames each taken over 0.3\% \w rotation with 150 s
exposure time.
;
_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  0.1695
_diffrn_reflns_av_sigmaI/netI    0.1350
_diffrn_reflns_limit_h_max       6
_diffrn_reflns_limit_h_min       -6
_diffrn_reflns_limit_k_max       32
_diffrn_reflns_limit_k_min       -42
_diffrn_reflns_limit_l_max       41
_diffrn_reflns_limit_l_min       -41
_diffrn_reflns_number            33425
_diffrn_reflns_theta_full        25.02
_diffrn_reflns_theta_max         25.02
_diffrn_reflns_theta_min         0.81
_diffrn_standards_number         0
_exptl_absorpt_coefficient_mu    0.095
_exptl_absorpt_correction_T_max  0.9983
_exptl_absorpt_correction_T_min  0.8756
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   'SADABS (Sheldrick, 1996)'
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    1.354
_exptl_crystal_density_meas      ?
_exptl_crystal_density_method    .
_exptl_crystal_description       needle
_exptl_crystal_F_000             3096
_exptl_crystal_size_max          0.540
_exptl_crystal_size_mid          0.020
_exptl_crystal_size_min          0.018
_refine_diff_density_max         0.447
_refine_diff_density_min         -0.366
_refine_diff_density_rms         0.091
_refine_ls_extinction_coef       0.0127(6)
_refine_ls_extinction_expression Fc^*^=kFc[1+0.001xFc^2^\l^3^/sin(2\q)]^-1/4^
_refine_ls_extinction_method     SHELXL
_refine_ls_goodness_of_fit_ref   1.037
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     726
_refine_ls_number_reflns         7087
_refine_ls_number_restraints     529
_refine_ls_restrained_S_all      1.018
_refine_ls_R_factor_all          0.2144
_refine_ls_R_factor_gt           0.0790
_refine_ls_shift/su_max          0.006
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0640P)^2^P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1387
_refine_ls_wR_factor_ref         0.1822
_reflns_number_gt                3234
_reflns_number_total             7087
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            b603080g.txt
_cod_original_sg_symbol_H-M      'P21 21 21'
_cod_original_formula_sum        'C20 H22.50 N3 O3.75'
_cod_database_code               7101186