data_A1IZ2 # _chem_comp.id A1IZ2 _chem_comp.name "(phenylmethyl) (2S)-5-[[N-[3-[(2R,3S,4R,5R)-5-(6-aminopurin-9-yl)-3,4-bis(oxidanyl)oxolan-2-yl]propyl]carbamimidoyl]amino]-2-(phenylmethoxycarbonylamino)pentanoate" _chem_comp.type non-polymer _chem_comp.pdbx_type HETAIN _chem_comp.formula "C33 H41 N9 O7" _chem_comp.mon_nstd_parent_comp_id ? _chem_comp.pdbx_synonyms ? _chem_comp.pdbx_formal_charge 0 _chem_comp.pdbx_initial_date 2025-01-28 _chem_comp.pdbx_modified_date 2026-01-23 _chem_comp.pdbx_ambiguous_flag N _chem_comp.pdbx_release_status REL _chem_comp.pdbx_replaced_by ? _chem_comp.pdbx_replaces ? _chem_comp.formula_weight 675.735 _chem_comp.one_letter_code ? _chem_comp.three_letter_code A1IZ2 _chem_comp.pdbx_model_coordinates_details ? _chem_comp.pdbx_model_coordinates_missing_flag N _chem_comp.pdbx_ideal_coordinates_details Corina _chem_comp.pdbx_ideal_coordinates_missing_flag N _chem_comp.pdbx_model_coordinates_db_code 9I1T _chem_comp.pdbx_subcomponent_list ? _chem_comp.pdbx_processing_site PDBE _chem_comp.pdbx_pcm ? # loop_ _chem_comp_atom.comp_id _chem_comp_atom.atom_id _chem_comp_atom.alt_atom_id _chem_comp_atom.type_symbol _chem_comp_atom.charge _chem_comp_atom.pdbx_align _chem_comp_atom.pdbx_aromatic_flag _chem_comp_atom.pdbx_leaving_atom_flag _chem_comp_atom.pdbx_stereo_config _chem_comp_atom.pdbx_n_terminal_atom_flag _chem_comp_atom.pdbx_backbone_atom_flag _chem_comp_atom.pdbx_c_terminal_atom_flag _chem_comp_atom.model_Cartn_x _chem_comp_atom.model_Cartn_y _chem_comp_atom.model_Cartn_z _chem_comp_atom.pdbx_model_Cartn_x_ideal _chem_comp_atom.pdbx_model_Cartn_y_ideal _chem_comp_atom.pdbx_model_Cartn_z_ideal _chem_comp_atom.pdbx_component_atom_id _chem_comp_atom.pdbx_component_comp_id _chem_comp_atom.pdbx_ordinal A1IZ2 C C1 C 0 1 N N N N Y Y 48.144 26.286 132.280 7.221 -0.522 -0.374 C A1IZ2 1 A1IZ2 C1 C2 C 0 1 N N N N N N 46.897 25.149 133.950 9.032 -2.042 -0.675 C1 A1IZ2 2 A1IZ2 C21 C3 C 0 1 Y N N N N N 47.239 23.868 134.651 9.402 -3.465 -0.347 C23 A1IZ2 3 A1IZ2 C26 C4 C 0 1 Y N N N N N 48.530 23.357 134.614 10.044 -3.756 0.843 C3 A1IZ2 4 A1IZ2 C25 C5 C 0 1 Y N N N N N 48.846 22.188 135.286 10.384 -5.062 1.144 C24 A1IZ2 5 A1IZ2 O O1 O 0 1 N N N N Y Y 48.413 27.179 133.035 7.887 0.293 -0.966 O A1IZ2 6 A1IZ2 C24 C6 C 0 1 Y N N N N N 47.879 21.514 136.001 10.081 -6.077 0.255 C25 A1IZ2 7 A1IZ2 C23 C7 C 0 1 Y N N N N N 46.593 22.008 136.041 9.439 -5.786 -0.934 C26 A1IZ2 8 A1IZ2 C22 C8 C 0 1 Y N N N N N 46.273 23.177 135.371 9.095 -4.481 -1.233 C7 A1IZ2 9 A1IZ2 CA C9 C 0 1 N N S N Y N 48.455 26.299 130.792 5.846 -0.156 0.123 CA A1IZ2 10 A1IZ2 C9 C10 C 0 1 N N N N N N 47.655 27.475 128.809 5.970 2.235 0.574 C9 A1IZ2 11 A1IZ2 OXT O2 O 0 1 N N N N Y Y 47.506 25.169 132.628 7.703 -1.757 -0.163 OXT A1IZ2 12 A1IZ2 O2 O3 O 0 1 N N N N N N 48.101 26.660 128.029 6.587 1.982 1.590 O2 A1IZ2 13 A1IZ2 C10 C11 C 0 1 N N N N N N 46.792 28.815 127.035 6.181 4.539 1.162 C10 A1IZ2 14 A1IZ2 C11 C12 C 0 1 Y N N N N N 45.364 29.215 126.792 5.791 5.898 0.640 C11 A1IZ2 15 A1IZ2 C12 C13 C 0 1 Y N N N N N 44.328 28.581 127.466 4.583 6.459 1.009 C12 A1IZ2 16 A1IZ2 N N1 N 0 1 N N N Y Y N 47.752 27.395 130.146 5.555 1.236 -0.229 N A1IZ2 17 A1IZ2 C13 C14 C 0 1 Y N N N N N 43.011 28.950 127.244 4.225 7.706 0.530 C13 A1IZ2 18 A1IZ2 C14 C15 C 0 1 Y N N N N N 42.712 29.955 126.349 5.075 8.390 -0.319 C14 A1IZ2 19 A1IZ2 C15 C16 C 0 1 Y N N N N N 43.732 30.592 125.675 6.283 7.828 -0.688 C15 A1IZ2 20 A1IZ2 C16 C17 C 0 1 Y N N N N N 45.050 30.226 125.894 6.643 6.585 -0.204 C16 A1IZ2 21 A1IZ2 CB C18 C 0 1 N N N N N N 49.968 26.398 130.571 4.808 -1.074 -0.525 CB A1IZ2 22 A1IZ2 CG C19 C 0 1 N N N N N N 50.484 27.810 130.307 3.429 -0.785 0.071 CG A1IZ2 23 A1IZ2 CD C20 C 0 1 N N N N N N 51.452 28.267 131.384 2.391 -1.704 -0.577 CD A1IZ2 24 A1IZ2 CZ C21 C 0 1 N N N N N N 52.826 30.298 131.875 -0.027 -2.135 -0.437 CZ A1IZ2 25 A1IZ2 "C7'" C22 C 0 1 N N N N N N 52.118 32.502 130.946 -2.435 -2.630 -0.360 C21 A1IZ2 26 A1IZ2 "C6'" C23 C 0 1 N N N N N N 52.346 33.969 131.285 -3.679 -2.150 0.390 C22 A1IZ2 27 A1IZ2 "C5'" C24 C 0 1 N N N N N N 51.233 34.865 130.752 -4.900 -2.937 -0.090 "C5'" A1IZ2 28 A1IZ2 "C4'" C25 C 0 1 N N R N N N 50.929 36.063 131.632 -6.144 -2.457 0.661 "C4'" A1IZ2 29 A1IZ2 "C1'" C26 C 0 1 N N R N N N 50.151 38.066 130.688 -7.887 -0.964 0.604 "C1'" A1IZ2 30 A1IZ2 C8 C27 C 0 1 Y N N N N N 50.234 37.934 128.159 -8.030 0.627 -1.350 C8 A1IZ2 31 A1IZ2 C5 C28 C 0 1 Y N N N N N 50.520 39.972 127.622 -9.828 1.745 -0.879 C5 A1IZ2 32 A1IZ2 C6 C29 C 0 1 Y N N N N N 50.723 41.222 127.020 -10.943 2.596 -0.803 C6 A1IZ2 33 A1IZ2 C2 C30 C 0 1 Y N N N N N 50.683 42.125 129.150 -11.547 1.571 1.176 C2 A1IZ2 34 A1IZ2 C4 C31 C 0 1 Y N N N N N 50.426 39.938 129.004 -9.640 0.804 0.147 C4 A1IZ2 35 A1IZ2 "C2'" C32 C 0 1 N N R N N N 48.943 37.156 130.905 -8.540 -2.318 0.246 "C2'" A1IZ2 36 A1IZ2 "C3'" C33 C 0 1 N N S N N N 49.463 36.245 132.019 -7.367 -3.322 0.284 "C3'" A1IZ2 37 A1IZ2 NE N2 N 0 1 N N N N N N 51.759 29.687 131.279 1.070 -1.427 -0.006 NE A1IZ2 38 A1IZ2 NH2 N3 N 0 1 N N N N N N 53.638 29.608 132.613 0.108 -3.051 -1.354 NH1 A1IZ2 39 A1IZ2 NH1 N4 N 0 1 N N N N N N 53.005 31.633 131.705 -1.266 -1.876 0.099 NH2 A1IZ2 40 A1IZ2 N9 N5 N 0 1 Y N N N N N 50.252 38.624 129.345 -8.496 0.118 -0.174 N9 A1IZ2 41 A1IZ2 N7 N6 N 0 1 Y N N N N N 50.392 38.687 127.102 -8.813 1.581 -1.762 N7 A1IZ2 42 A1IZ2 N6 N7 N 0 1 N N N N N N 50.872 41.401 125.701 -11.181 3.543 -1.784 N6 A1IZ2 43 A1IZ2 N1 N8 N 0 1 Y N N N N N 50.800 42.302 127.830 -11.765 2.471 0.234 N1 A1IZ2 44 A1IZ2 N3 N9 N 0 1 Y N N N N N 50.497 40.992 129.828 -10.516 0.753 1.145 N3 A1IZ2 45 A1IZ2 O3 O4 O 0 1 N N N N N N 46.976 28.585 128.457 5.703 3.515 0.251 O3 A1IZ2 46 A1IZ2 "O4'" O5 O 0 1 N N N N N N 51.300 37.271 130.929 -6.496 -1.119 0.247 "O4'" A1IZ2 47 A1IZ2 "O2'" O6 O 0 1 N N N N N N 47.807 37.902 131.322 -9.531 -2.667 1.214 "O2'" A1IZ2 48 A1IZ2 "O3'" O7 O 0 1 N N N N N N 49.334 36.855 133.298 -7.597 -4.323 1.278 "O3'" A1IZ2 49 A1IZ2 H4 H1 H 0 1 N N N N N N 47.274 25.998 134.538 9.751 -1.364 -0.215 H4 A1IZ2 50 A1IZ2 H5 H2 H 0 1 N N N N N N 45.805 25.229 133.849 9.042 -1.904 -1.756 H5 A1IZ2 51 A1IZ2 H6 H3 H 0 1 N N N N N N 49.295 23.876 134.056 10.280 -2.963 1.537 H6 A1IZ2 52 A1IZ2 H7 H4 H 0 1 N N N N N N 49.854 21.803 135.250 10.885 -5.289 2.073 H7 A1IZ2 53 A1IZ2 H1 H5 H 0 1 N N N N N N 48.128 20.604 136.527 10.347 -7.097 0.490 H1 A1IZ2 54 A1IZ2 H9 H6 H 0 1 N N N N N N 45.832 21.481 136.597 9.203 -6.580 -1.628 H9 A1IZ2 55 A1IZ2 H10 H7 H 0 1 N N N N N N 45.262 23.555 135.409 8.590 -4.255 -2.160 H10 A1IZ2 56 A1IZ2 HA H8 H 0 1 N N N N Y N 48.110 25.348 130.361 5.808 -0.272 1.206 HA A1IZ2 57 A1IZ2 H13 H9 H 0 1 N N N N N N 47.018 27.893 126.479 7.266 4.478 1.240 H13 A1IZ2 58 A1IZ2 H12 H10 H 0 1 N N N N N N 47.464 29.619 126.700 5.736 4.386 2.145 H12 A1IZ2 59 A1IZ2 H14 H11 H 0 1 N N N N N N 44.551 27.793 128.170 3.919 5.925 1.672 H14 A1IZ2 60 A1IZ2 H H12 H 0 1 N N N Y Y N 47.331 28.106 130.710 5.063 1.439 -1.040 H A1IZ2 61 A1IZ2 H15 H13 H 0 1 N N N N N N 42.215 28.448 127.774 3.281 8.144 0.818 H15 A1IZ2 62 A1IZ2 H16 H14 H 0 1 N N N N N N 41.685 30.242 126.177 4.795 9.363 -0.694 H16 A1IZ2 63 A1IZ2 H17 H15 H 0 1 N N N N N N 43.502 31.380 124.973 6.949 8.365 -1.348 H17 A1IZ2 64 A1IZ2 H18 H16 H 0 1 N N N N N N 45.841 30.732 125.361 7.587 6.146 -0.493 H18 A1IZ2 65 A1IZ2 HB2 H17 H 0 1 N N N N N N 50.230 25.771 129.706 4.784 -0.893 -1.600 HB2 A1IZ2 66 A1IZ2 HB3 H18 H 0 1 N N N N N N 50.471 26.012 131.470 5.075 -2.114 -0.338 HB3 A1IZ2 67 A1IZ2 HG3 H19 H 0 1 N N N N N N 50.999 27.825 129.335 3.453 -0.966 1.146 HG3 A1IZ2 68 A1IZ2 HG2 H20 H 0 1 N N N N N N 49.629 28.502 130.279 3.162 0.255 -0.116 HG2 A1IZ2 69 A1IZ2 HD3 H21 H 0 1 N N N N N N 51.003 28.073 132.369 2.366 -1.523 -1.652 HD3 A1IZ2 70 A1IZ2 HD2 H22 H 0 1 N N N N N N 52.386 27.694 131.287 2.657 -2.743 -0.389 HD2 A1IZ2 71 A1IZ2 H28 H23 H 0 1 N N N N N N 51.076 32.240 131.179 -2.282 -3.691 -0.168 H28 A1IZ2 72 A1IZ2 H29 H24 H 0 1 N N N N N N 52.303 32.351 129.872 -2.573 -2.471 -1.430 H29 A1IZ2 73 A1IZ2 H30 H25 H 0 1 N N N N N N 53.301 34.290 130.843 -3.542 -2.309 1.460 H30 A1IZ2 74 A1IZ2 H31 H26 H 0 1 N N N N N N 52.393 34.076 132.379 -3.833 -1.088 0.198 H31 A1IZ2 75 A1IZ2 "H5''" H27 H 0 0 N N N N N N 51.531 35.232 129.759 -5.037 -2.778 -1.159 "H5''" A1IZ2 76 A1IZ2 "H5'" H28 H 0 1 N N N N N N 50.318 34.262 130.661 -4.747 -3.999 0.103 "H5'" A1IZ2 77 A1IZ2 "H4'" H29 H 0 1 N N N N N N 51.523 35.979 132.554 -5.973 -2.490 1.737 "H4'" A1IZ2 78 A1IZ2 "H1'" H30 H 0 1 N N N N N N 50.104 38.886 131.420 -7.985 -0.766 1.671 "H1'" A1IZ2 79 A1IZ2 H8 H31 H 0 1 N N N N N N 50.101 36.864 128.104 -7.141 0.290 -1.861 H8 A1IZ2 80 A1IZ2 H2 H32 H 0 1 N N N N N N 50.748 43.022 129.749 -12.240 1.504 2.001 H2 A1IZ2 81 A1IZ2 "H2'" H33 H 0 1 N N N N N N 48.738 36.570 129.997 -8.979 -2.278 -0.751 "H2'" A1IZ2 82 A1IZ2 "H3'" H34 H 0 1 N N N N N N 48.943 35.276 131.982 -7.224 -3.780 -0.694 "H3'" A1IZ2 83 A1IZ2 HE H35 H 0 1 N N N N N N 51.145 30.255 130.732 0.970 -0.746 0.677 HE A1IZ2 84 A1IZ2 HH11 H36 H 0 0 N N N N N N 54.361 30.176 133.006 -0.666 -3.550 -1.658 HH11 A1IZ2 85 A1IZ2 HH21 H38 H 0 0 N N N N N N 53.806 32.050 132.133 -1.367 -1.194 0.782 HH21 A1IZ2 86 A1IZ2 H61 H39 H 0 1 N N N N N N 51.027 42.370 125.511 -10.573 3.624 -2.536 H61 A1IZ2 87 A1IZ2 H62 H40 H 0 1 N N N N N N 51.655 40.869 125.379 -11.954 4.124 -1.720 H62 A1IZ2 88 A1IZ2 "HO2'" H41 H 0 0 N N N N N N 47.071 37.315 131.450 -9.973 -3.509 1.038 "HO2'" A1IZ2 89 A1IZ2 "HO3'" H42 H 0 0 N N N N N N 49.665 36.265 133.965 -8.354 -4.896 1.091 "HO3'" A1IZ2 90 # loop_ _chem_comp_bond.comp_id _chem_comp_bond.atom_id_1 _chem_comp_bond.atom_id_2 _chem_comp_bond.value_order _chem_comp_bond.pdbx_aromatic_flag _chem_comp_bond.pdbx_stereo_config _chem_comp_bond.pdbx_ordinal A1IZ2 C15 C16 DOUB Y N 1 A1IZ2 C15 C14 SING Y N 2 A1IZ2 N6 C6 SING N N 3 A1IZ2 C16 C11 SING Y N 4 A1IZ2 C14 C13 DOUB Y N 5 A1IZ2 C11 C10 SING N N 6 A1IZ2 C11 C12 DOUB Y N 7 A1IZ2 C6 C5 SING Y N 8 A1IZ2 C6 N1 DOUB Y N 9 A1IZ2 C10 O3 SING N N 10 A1IZ2 N7 C5 SING Y N 11 A1IZ2 N7 C8 DOUB Y N 12 A1IZ2 C13 C12 SING Y N 13 A1IZ2 C5 C4 DOUB Y N 14 A1IZ2 N1 C2 SING Y N 15 A1IZ2 O2 C9 DOUB N N 16 A1IZ2 C8 N9 SING Y N 17 A1IZ2 O3 C9 SING N N 18 A1IZ2 C9 N SING N N 19 A1IZ2 C4 N9 SING Y N 20 A1IZ2 C4 N3 SING Y N 21 A1IZ2 C2 N3 DOUB Y N 22 A1IZ2 N9 "C1'" SING N N 23 A1IZ2 N CA SING N N 24 A1IZ2 CG CB SING N N 25 A1IZ2 CG CD SING N N 26 A1IZ2 CB CA SING N N 27 A1IZ2 "C1'" "C2'" SING N N 28 A1IZ2 "C1'" "O4'" SING N N 29 A1IZ2 "C5'" "C6'" SING N N 30 A1IZ2 "C5'" "C4'" SING N N 31 A1IZ2 CA C SING N N 32 A1IZ2 "C2'" "O2'" SING N N 33 A1IZ2 "C2'" "C3'" SING N N 34 A1IZ2 "O4'" "C4'" SING N N 35 A1IZ2 "C7'" "C6'" SING N N 36 A1IZ2 "C7'" NH1 SING N N 37 A1IZ2 NE CD SING N N 38 A1IZ2 NE CZ SING N N 39 A1IZ2 "C4'" "C3'" SING N N 40 A1IZ2 NH1 CZ SING N N 41 A1IZ2 CZ NH2 DOUB N N 42 A1IZ2 "C3'" "O3'" SING N N 43 A1IZ2 C OXT SING N N 44 A1IZ2 C O DOUB N N 45 A1IZ2 OXT C1 SING N N 46 A1IZ2 C1 C21 SING N N 47 A1IZ2 C26 C21 DOUB Y N 48 A1IZ2 C26 C25 SING Y N 49 A1IZ2 C21 C22 SING Y N 50 A1IZ2 C25 C24 DOUB Y N 51 A1IZ2 C22 C23 DOUB Y N 52 A1IZ2 C24 C23 SING Y N 53 A1IZ2 C1 H4 SING N N 54 A1IZ2 C1 H5 SING N N 55 A1IZ2 C26 H6 SING N N 56 A1IZ2 C25 H7 SING N N 57 A1IZ2 C24 H1 SING N N 58 A1IZ2 C23 H9 SING N N 59 A1IZ2 C22 H10 SING N N 60 A1IZ2 CA HA SING N N 61 A1IZ2 C10 H13 SING N N 62 A1IZ2 C10 H12 SING N N 63 A1IZ2 C12 H14 SING N N 64 A1IZ2 N H SING N N 65 A1IZ2 C13 H15 SING N N 66 A1IZ2 C14 H16 SING N N 67 A1IZ2 C15 H17 SING N N 68 A1IZ2 C16 H18 SING N N 69 A1IZ2 CB HB2 SING N N 70 A1IZ2 CB HB3 SING N N 71 A1IZ2 CG HG3 SING N N 72 A1IZ2 CG HG2 SING N N 73 A1IZ2 CD HD3 SING N N 74 A1IZ2 CD HD2 SING N N 75 A1IZ2 "C7'" H28 SING N N 76 A1IZ2 "C7'" H29 SING N N 77 A1IZ2 "C6'" H30 SING N N 78 A1IZ2 "C6'" H31 SING N N 79 A1IZ2 "C5'" "H5''" SING N N 80 A1IZ2 "C5'" "H5'" SING N N 81 A1IZ2 "C4'" "H4'" SING N N 82 A1IZ2 "C1'" "H1'" SING N N 83 A1IZ2 C8 H8 SING N N 84 A1IZ2 C2 H2 SING N N 85 A1IZ2 "C2'" "H2'" SING N N 86 A1IZ2 "C3'" "H3'" SING N N 87 A1IZ2 NE HE SING N N 88 A1IZ2 NH2 HH11 SING N N 89 A1IZ2 NH1 HH21 SING N N 90 A1IZ2 N6 H61 SING N N 91 A1IZ2 N6 H62 SING N N 92 A1IZ2 "O2'" "HO2'" SING N N 93 A1IZ2 "O3'" "HO3'" SING N N 94 # loop_ _pdbx_chem_comp_descriptor.comp_id _pdbx_chem_comp_descriptor.type _pdbx_chem_comp_descriptor.program _pdbx_chem_comp_descriptor.program_version _pdbx_chem_comp_descriptor.descriptor A1IZ2 InChI InChI 1.06 "InChI=1S/C33H41N9O7/c34-28-25-29(39-19-38-28)42(20-40-25)30-27(44)26(43)24(49-30)14-8-16-37-32(35)36-15-7-13-23(31(45)47-17-21-9-3-1-4-10-21)41-33(46)48-18-22-11-5-2-6-12-22/h1-6,9-12,19-20,23-24,26-27,30,43-44H,7-8,13-18H2,(H,41,46)(H2,34,38,39)(H3,35,36,37)/t23-,24+,26+,27+,30+/m0/s1" A1IZ2 InChIKey InChI 1.06 PJQUMOMSXLCGOK-CCJJPLMQSA-N A1IZ2 SMILES_CANONICAL CACTVS 3.385 "Nc1ncnc2n(cnc12)[C@@H]3O[C@H](CCCNC(=N)NCCC[C@H](NC(=O)OCc4ccccc4)C(=O)OCc5ccccc5)[C@@H](O)[C@H]3O" A1IZ2 SMILES CACTVS 3.385 "Nc1ncnc2n(cnc12)[CH]3O[CH](CCCNC(=N)NCCC[CH](NC(=O)OCc4ccccc4)C(=O)OCc5ccccc5)[CH](O)[CH]3O" A1IZ2 SMILES_CANONICAL "OpenEye OEToolkits" 2.0.7 "[H]/N=C(\NCCC[C@@H]1[C@H]([C@H]([C@@H](O1)n2cnc3c2ncnc3N)O)O)/NCCC[C@@H](C(=O)OCc4ccccc4)NC(=O)OCc5ccccc5" A1IZ2 SMILES "OpenEye OEToolkits" 2.0.7 "c1ccc(cc1)COC(=O)C(CCCNC(=N)NCCCC2C(C(C(O2)n3cnc4c3ncnc4N)O)O)NC(=O)OCc5ccccc5" # _pdbx_chem_comp_identifier.comp_id A1IZ2 _pdbx_chem_comp_identifier.type "SYSTEMATIC NAME" _pdbx_chem_comp_identifier.program "OpenEye OEToolkits" _pdbx_chem_comp_identifier.program_version 2.0.7 _pdbx_chem_comp_identifier.identifier "(phenylmethyl) (2~{S})-5-[[~{N}-[3-[(2~{R},3~{S},4~{R},5~{R})-5-(6-aminopurin-9-yl)-3,4-bis(oxidanyl)oxolan-2-yl]propyl]carbamimidoyl]amino]-2-(phenylmethoxycarbonylamino)pentanoate" # loop_ _pdbx_chem_comp_audit.comp_id _pdbx_chem_comp_audit.action_type _pdbx_chem_comp_audit.date _pdbx_chem_comp_audit.processing_site A1IZ2 "Create component" 2025-01-28 PDBE A1IZ2 "Initial release" 2026-01-28 RCSB #