Hi All, I am trying to add charges to nicotinamide adenine dinucleotide (NAD+) using UCSF Chimera; the total charge on this molecule should be -1 (assuming the ionization of NAD+ at pH ~7.0, see attached figure). When I add Gasteiger charges, the total charge sums up incorrectly to 0, even though the net charge specified in the drop-down box is -1. However, using the "AM1-BCC" method, the net charge correctly sums up to -1. The charge model used is "Amber ff99SB". I have also noticed that the partial charges on individual atoms assigned when using the "AM1-BCC" method are generally of greater magnitude compared to charges assigned using the Gasteiger method. I am wondering why the Gasteiger method assigns an incorrect net charge in the case of NAD+. The mol2 structure code (with incorrect Gasteiger charges) is written below (and attached as NAD.mol2 with corresponding PNG structure image). Thanks in advance, Nancy ============================================================================ @<TRIPOS>MOLECULE NAD.mol2 70 74 1 0 0 SMALL USER_CHARGES @<TRIPOS>ATOM 1 C1 -1.4117 5.8700 -3.4377 C.2 1 LIG1 -0.0471 2 C2 -0.2808 5.1989 -2.9922 C.2 1 LIG1 -0.0472 3 C3 0.0698 5.2540 -1.6463 C.2 1 LIG1 -0.0021 4 N1 -0.7125 5.8930 -0.7233 N.2 1 LIG1 -0.2845 5 C4 -1.7621 6.6431 -1.1880 C.2 1 LIG1 0.0105 6 C5 -2.1590 6.6215 -2.5315 C.2 1 LIG1 0.0510 7 C6 -3.3433 7.3892 -2.9991 C.2 1 LIG1 0.2416 8 O1 -3.7255 7.3875 -4.2002 O.2 1 LIG1 -0.2721 9 N2 -4.0978 8.1475 -2.0847 N.3 1 LIG1 -0.3250 10 O2 0.0324 4.4339 0.9916 O.3 1 LIG1 -0.3484 11 C7 -1.0355 3.6965 1.6402 C.3 1 LIG1 0.1165 12 C8 -1.4243 2.4599 0.8071 C.3 1 LIG1 0.1276 13 O3 -0.4100 1.4351 0.9207 O.3 1 LIG1 -0.1602 14 P1 0.8613 1.4216 -0.0633 P.3 1 LIG1 0.5624 15 O4 2.0180 2.1020 0.5580 O.2 1 LIG1 -0.3429 16 O5 0.5634 2.0116 -1.3891 O.3 1 LIG1 -0.3429 17 O6 1.1223 -0.1529 -0.1877 O.3 1 LIG1 0.0575 18 P2 0.0541 -1.2893 -0.5527 P.3 1 LIG1 0.5624 19 O7 -1.1823 -1.2052 0.2607 O.3 1 LIG1 -0.3429 20 O8 0.6340 -2.6390 -0.3765 O.2 1 LIG1 -0.3429 21 O9 -0.2208 -1.0077 -2.1109 O.3 1 LIG1 -0.1602 22 O10 -2.0844 -2.0838 -4.0533 O.3 1 LIG1 -0.3483 23 C9 -1.7580 -0.6726 -3.9721 C.3 1 LIG1 0.1165 24 C10 -1.4291 -0.3206 -2.5098 C.3 1 LIG1 0.1276 25 N3 -5.5165 -1.9977 -1.1853 N.2 1 LIG1 -0.2341 26 C11 -5.3009 -1.7637 -2.4944 C.2 1 LIG1 0.0912 27 N4 -4.1259 -2.3733 -2.8716 N.3 1 LIG1 -0.2445 28 C12 -3.5825 -3.0679 -1.8327 C.2 1 LIG1 0.1583 29 C13 -4.4622 -2.7976 -0.7674 C.2 1 LIG1 0.1418 30 N5 -2.5159 -3.8010 -1.6563 N.2 1 LIG1 -0.2186 31 C14 -2.2518 -4.3018 -0.4707 C.2 1 LIG1 0.1192 32 N6 -3.0604 -4.0697 0.5431 N.2 1 LIG1 -0.2228 33 C15 -4.1365 -3.3442 0.4336 C.2 1 LIG1 0.1340 34 N7 -4.8438 -3.2010 1.5627 N.3 1 LIG1 -0.2849 35 C16 -2.1891 4.7099 1.7524 C.3 1 LIG1 0.1128 36 C17 -1.4568 6.0605 1.7533 C.3 1 LIG1 0.1256 37 C18 -0.3444 5.8071 0.7094 C.3 1 LIG1 0.1560 38 C19 -3.0362 0.0509 -4.4501 C.3 1 LIG1 0.1128 39 C20 -3.9053 -1.0632 -5.0633 C.3 1 LIG1 0.1257 40 C21 -3.5098 -2.2874 -4.2107 C.3 1 LIG1 0.1588 41 O11 -2.9991 4.5200 2.9209 O.3 1 LIG1 -0.3874 42 O12 -0.8413 6.3227 3.0256 O.3 1 LIG1 -0.3858 43 O13 -3.5425 -1.3145 -6.4282 O.3 1 LIG1 -0.3858 44 O14 -2.7472 1.1126 -5.3700 O.3 1 LIG1 -0.3874 45 H1 -1.6809 5.8357 -4.4909 H 1 LIG1 0.0632 46 H2 0.3396 4.6461 -3.6934 H 1 LIG1 0.0636 47 H3 0.9656 4.7572 -1.2733 H 1 LIG1 0.0793 48 H4 -2.2796 7.2615 -0.4632 H 1 LIG1 0.0801 49 H5 -4.8503 8.7190 -2.4374 H 1 LIG1 0.1458 50 H6 -3.7587 8.2854 -1.1465 H 1 LIG1 0.1458 51 H7 -0.6981 3.4004 2.6380 H 1 LIG1 0.0660 52 H8 -1.5845 2.7299 -0.2407 H 1 LIG1 0.0645 53 H9 -2.3510 2.0430 1.2095 H 1 LIG1 0.0645 54 H10 -0.9095 -0.4615 -4.6296 H 1 LIG1 0.0660 55 H11 -1.2870 0.7565 -2.4090 H 1 LIG1 0.0645 56 H12 -2.2603 -0.6329 -1.8739 H 1 LIG1 0.0645 57 H13 -5.9324 -1.1833 -3.1491 H 1 LIG1 0.1018 58 H14 -1.3609 -4.8928 -0.3242 H 1 LIG1 0.1064 59 H15 -4.6910 -3.8437 2.3366 H 1 LIG1 0.1259 60 H16 -5.8375 -2.9879 1.5154 H 1 LIG1 0.1259 61 H17 -2.8150 4.6581 0.8568 H 1 LIG1 0.0659 62 H18 -2.1232 6.8857 1.5028 H 1 LIG1 0.0675 63 H19 0.5295 6.4594 0.8618 H 1 LIG1 0.0853 64 H20 -3.5627 0.4623 -3.5840 H 1 LIG1 0.0659 65 H21 -4.9700 -0.8302 -5.0011 H 1 LIG1 0.0675 66 H22 -3.6913 -3.2429 -4.7274 H 1 LIG1 0.0854 67 H23 -3.4491 3.6578 2.8683 H 1 LIG1 0.2107 68 H24 -0.3142 7.1392 2.9619 H 1 LIG1 0.2108 69 H25 -3.3167 -0.4612 -6.8446 H 1 LIG1 0.2108 70 H26 -3.5789 1.5634 -5.6077 H 1 LIG1 0.2107 @<TRIPOS>BOND 1 1 45 1 2 1 2 ar 3 1 6 ar 4 2 46 1 5 2 3 ar 6 3 47 1 7 3 4 ar 8 4 5 ar 9 5 48 1 10 5 6 ar 11 6 7 1 12 7 9 am 13 7 8 2 14 9 50 1 15 9 49 1 16 10 11 1 17 10 37 1 18 11 35 1 19 11 51 1 20 11 12 1 21 12 53 1 22 12 52 1 23 12 13 1 24 13 14 1 25 14 17 1 26 14 16 1 27 14 15 1 28 17 18 1 29 18 21 1 30 18 20 1 31 18 19 1 32 22 40 1 33 22 23 1 34 23 24 1 35 23 54 1 36 23 38 1 37 24 21 1 38 24 56 1 39 24 55 1 40 25 29 ar 41 25 26 ar 42 26 57 1 43 26 27 ar 44 27 28 ar 45 28 30 ar 46 29 33 ar 47 29 28 ar 48 30 31 ar 49 31 58 1 50 31 32 ar 51 32 33 ar 52 33 34 1 53 34 60 1 54 34 59 1 55 35 36 1 56 35 61 1 57 35 41 1 58 36 37 1 59 36 62 1 60 36 42 1 61 37 4 1 62 37 63 1 63 38 64 1 64 38 44 1 65 38 39 1 66 39 65 1 67 39 43 1 68 39 40 1 69 40 27 1 70 40 66 1 71 41 67 1 72 42 68 1 73 43 69 1 74 44 70 1 @<TRIPOS>SUBSTRUCTURE 1 LIG1 1 GROUP 1 LIG 1 ============================================================================
