Why lamivudine assembles into double-stranded helices in crystals: salt heterosynthon versus base-pairing homosynthon
da Silva, Cameron Capeletti; Valdo, Ana K.; do Nascimento Neto, José Antônio; Ribeiro, Leandro; Sarotti, Ariel M.; Martins, Felipe Terra; CrystEngComm 20 (2018) 3049–; doi:10.1039/C8CE00100F

data_7230546
_publ_section_title
;
 Why lamivudine assembles into double-stranded helices in crystals: salt
 heterosynthon versus base-pairing homosynthon
;
_journal_issue                   22
_journal_name_full               CrystEngComm
_journal_page_first              3049
_journal_paper_doi               10.1039/C8CE00100F
_journal_volume                  20
_journal_year                    2018
_chemical_absolute_configuration rmad
_chemical_formula_moiety         '2(C8 H12 N3 O3 S), O4 S'
_chemical_formula_sum            'C16 H24 N6 O10 S3'
_chemical_formula_weight         556.59
_chemical_name_common            'lamivudine sulfate'
_space_group_crystal_system      orthorhombic
_space_group_IT_number           19
_space_group_name_Hall           'P 2ac 2ab'
_space_group_name_H-M_alt        'P 21 21 21'
_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-2014
_audit_update_record
;
2017-10-14 deposited with the CCDC.
2018-04-23 downloaded from the CCDC.
;
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   6.7148(14)
_cell_length_b                   17.982(6)
_cell_length_c                   19.374(5)
_cell_measurement_reflns_used    1476
_cell_measurement_temperature    296(2)
_cell_measurement_theta_max      21.21
_cell_measurement_theta_min      2.39
_cell_volume                     2339.3(11)
_computing_structure_refinement  'SHELXL-2014 (Sheldrick, 2014)'
_diffrn_ambient_temperature      296(2)
_diffrn_measured_fraction_theta_full 0.995
_diffrn_measured_fraction_theta_max 0.983
_diffrn_measurement_device_type  'Bruker APEX-II CCD'
_diffrn_measurement_method       '\f and \w scans'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0393
_diffrn_reflns_av_unetI/netI     0.0786
_diffrn_reflns_Laue_measured_fraction_full 0.995
_diffrn_reflns_Laue_measured_fraction_max 0.983
_diffrn_reflns_limit_h_max       4
_diffrn_reflns_limit_h_min       -8
_diffrn_reflns_limit_k_max       21
_diffrn_reflns_limit_k_min       -13
_diffrn_reflns_limit_l_max       23
_diffrn_reflns_limit_l_min       -9
_diffrn_reflns_number            6148
_diffrn_reflns_point_group_measured_fraction_full 0.891
_diffrn_reflns_point_group_measured_fraction_max 0.876
_diffrn_reflns_theta_full        25.000
_diffrn_reflns_theta_max         25.459
_diffrn_reflns_theta_min         2.388
_exptl_absorpt_coefficient_mu    0.383
_exptl_absorpt_correction_T_max  0.974
_exptl_absorpt_correction_T_min  0.779
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details
'Blessing, R. H. (1995) Acta Cryst., A51, 33-38'
_exptl_crystal_density_diffrn    1.580
_exptl_crystal_description       needle
_exptl_crystal_F_000             1160
_exptl_crystal_size_max          0.2
_exptl_crystal_size_mid          0.1
_exptl_crystal_size_min          0.07
_refine_diff_density_max         0.268
_refine_diff_density_min         -0.312
_refine_diff_density_rms         0.063
_refine_ls_abs_structure_details
;
 Flack x determined using 750 quotients [(I+)-(I-)]/[(I+)+(I-)]
 (Parsons, Flack and Wagner, Acta Cryst. B69 (2013) 249-259).
;
_refine_ls_abs_structure_Flack   0.02(7)
_refine_ls_extinction_coef       0.0034(8)
_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   1.024
_refine_ls_hydrogen_treatment    constr
_refine_ls_matrix_type           full
_refine_ls_number_parameters     317
_refine_ls_number_reflns         3786
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.024
_refine_ls_R_factor_all          0.0806
_refine_ls_R_factor_gt           0.0488
_refine_ls_shift/su_max          0.000
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'w=1/[\s^2^(Fo^2^)+(0.0449P)^2^] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0978
_refine_ls_wR_factor_ref         0.1141
_reflns_Friedel_coverage         0.545
_reflns_Friedel_fraction_full    0.750
_reflns_Friedel_fraction_max     0.730
_reflns_number_gt                2582
_reflns_number_total             3786
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            c8ce00100f2.cif
_cod_data_source_block           shelxl_CCDC3
_cod_depositor_comments
'Adding full bibliography for 7230543--7230547.cif.'
_cod_database_code               7230546
_shelxl_version_number           2014-3
_shelx_res_checksum              15768