1. MMFFSYMB.PAR: This file specifies the four-character symbolic atom types 
                 used in MMFF and defines the numeric atom type to which each 
                 corresponds.
*
*          Copyright (c) Merck and Co., Inc., 1994, 1995, 1996
*                         All Rights Reserved
*
*
* SYMBOL TYPE  DEFINITION
*
  CR      1  ALKYL CARBON, SP3
  C=C     2  VINYLIC CARBON, SP2
  CSP2    2  GENERIC SP2 CARBON
  C=O     3  GENERAL CARBONYL CARBON
  C=N     3  SP2 CARBON IN C=N
  CGD     3  GUANIDINE CARBON, DOUBLY BONDED TO N
  C=OR    3  KETONE OR ALDEHYDE CARBONYL CARBON
  C=ON    3  AMIDE CARBONYL CARBON
  CONN    3  UREA CARBONYL CARBON
  COO     3  CARBOXYLIC ACID OR ESTER CARBONYL CARBON
  COON    3  CARBAMATE CARBONYL CARBON
  COOO    3  C ARBONIC ACID OR ESTER CARBONYL CARBON
  C=OS    3  THIOESTER CARBONYL CARBON, DOUBLE BONDED TO O
  C=S     3  THIOESTER CARBON, DOUBLY BONDED TO S
  C=SN    3  THIOAMIDE, CARBON, DOUBLY BONDED TO S
  CSO2    3  CARBON IN >C=SO2
  CS=O    3  CARBON IN >C=S=O (SULFINYL GROUP)
  CSS     3  THIOCARBOXYLIC ACID OR ESTER CARBONYL CARBON
  C=P     3  CARBON DOUBLE BONDED TO PHOSPHOROUS
  CSP     4  ACETYLENIC CARBON
  =C=     4  ALLENIC CARBON
  HC      5  H  ATTACHED TO C
  HSI     5  H ATTACHED TO SI
  OR      6  ALCOHOL OR ETHER OXYGEN
  OC=O    6  ESTER OR CARBOXYLIC ACID -O-
  OC=C    6  ENOLIC OR PHENOLIC OXYGEN
  OC=N    6  DIVALENT OXYGEN 
  OC=S    6  THIOESTER OR THIOACID -O-
  ONO2    6  DIVALENT NITRATE "ETHER" OXYGEN
  ON=O    6  DIVALENT NITRITE "ETHER" OXYGEN
  OSO3    6  DIVALENT OXYGEN ATTACHED TO SULFUR
  OSO2    6  DIVALENT OXYGEN ATTACHED TO SULFUR
  OSO     6  DIVALENT OXYGEN ATTACHED TO SULFUR
  OS=O    6  DIVALENT OXYGEN ATTACHED TO SULFOXIDE SULFUR
  -OS     6  GENERAL DIVALENT OX ATTACHED TO S
  OPO3    6  DIVALENT OXYGEN ATTACHED TO PHOSPHOROUS
  OPO2    6  DIVALENT OXYGEN ATTACHED TO PHOSPHOROUS
  OPO     6  DIVALENT OXYGEN ATTACHED TO PHOSPHOROUS
  -OP     6  DIVALENT OXYGEN ATTACHED TO PHOSPHOROUS
  -O-     6  GENERAL DIVALENT O
  O=C     7  GENERAL C=O
  O=CN    7  CARBONYL OXYGEN, AMIDES
  O=CR    7  CARBONYL OXYGEN, ALDEHYDES AND KETONES
  O=CO    7  CARBONYL OXYGEN, CARBOXYLIC ACIDS AND ESTERS
  O=N     7  NITROSO OXYGEN
  O=S     7  O=S IN SULFOXIDES
  O=S=    7  O=S ON SULFUR DOUBLY BONDED TO, E.G., CARBON
  NR      8  NITROGEN IN ALIPHATIC AMINES
  N=C     9  NITROGEN IN IMINES
  N=N     9  NITROGEN IN AZO COMPOUNDS
  NC=O   10  NITROGEN IN AMIDES
  NC=S   10  NITROGEN IN N-C=S, THIOAMIDE
  NN=C   10  NITROGEN IN N-N=C
  NN=N   10  NITROGEN IN N-N=N
  F      11  FLUORINE
  CL     12  CHLORINE
  BR     13  BROMINE
  I      14  IODINE
  S      15  SULFUR IN THIOETHERS AND MERCAPTANS
  S=C    16  TERMINAL SULFUR DOUBLY BONDED TO CARBON
  S=O    17  SULFUR IN SULFOXIDES
  >S=N   17  SULFUR, TRICOORD, DOUBLY BONDED TO N
  SO2    18  SULFUR IN SULFONES 
  SO2N   18  SULFUR IN SULFONAMIDES
  SO3    18  SULFONATE SULFUR
  SO4    18  SULFATE SULFUR
  =SO2   18  SULFONE SULPHER DOUBLY BONDED TO CARBON
  SNO    18  SULFUR IN NITROGEN ANALOG OF A SULFONE
  SI     19  SILICON
  CR4R   20  CARBON IN 4-MEMBERED RINGS
  HOR    21  HYDROGEN IN ALCOHOLS
  HO     21  GENERAL H ON OXYGEN
  HOM    21  HYDROGEN IN HYDROXIDE ANION
  CR3R   22  CARBON IN A 3-MEMBERED RING
  HNR    23  H-N(SP3)
  H3N    23  H-N(SP3), AMMONIA
  HPYL   23  H-N IN PYRROLE
  HNOX   23  H-N IN IN A N-OXIDE
  HNM    23  H ON DICOORD, NEGATIVELY CHARGED NITROGEN
  HN     23  GENERAL H ON NITROGEN
  HOCO   24  H-O IN CARBOXYLIC ACIDS
  HOP    24  HYDROGEN ON OXYGEN ATTACHED TO PHOSPHOROUS
  PO4    25  PHOSPHOROUS IN PHOSPHATES AND PHOSPHODIESTERS
  PO3    25  TETRACOORDINATE P WITH THREE ATTACHED OXYGENS
  PO2    25  TETRACOORDINATE P WITH TWO ATTACHED OXYGENS
  PO     25  TETRACOORDINATE P WITH ONE ATTACHED OXYGEN
  PTET   25  GENERAL TETRACOORDINATE PHOSPHORUS
  P      26  TRICOORDINATE P, AS IN PHOSPHINES
  HN=N   27  AZO HYDROGEN
  HN=C   27  IMINE HYDROGEN
  HNCO   28  AMIDE HYDROGEN
  HNCS   28  THIOAMIDE HYDROGEN
  HNCC   28  H-N IN ENAMINES
  HNCN   28  H-N IN H-N-C=N
  HNNC   28  H-N IN H-N-N=C
  HNNN   28  H-N IN H-N-N=N
  HNSO   28  H-N IN SULFONAMIDE
  HNPO   28  H-N IN PHOSPHONAMIDE
  HNC%   28  HYDROGEN ON N ATTACHED TO TRIPLY BONDED CARBON
  HSP2   28  GENERAL H ON SP2 NITROGEN
  HOCC   29  H-O IN ENOLS AND PHENOLS
  HOCN   29  H-O IN HO-C=N
  CE4R   30  OLEFINIC CARBON IN 4-MEMBERED RINGS
  HOH    31  HYDROGEN IN H2O
  O2CM   32  OXYGEN IN CARBOXYLATE ANION
  OXN    32  N-OXIDE OXYGEN
  O2N    32  NITRO OXYGEN
  O2NO   32  NITRO-GROUP OXYGEN IN NITRATE
  O3N    32  NITRATE ANION OXYGEN
  O-S    32  SINGLE TERMINAL OXYGEN ON TETRACOORD SULFUR
  O2S    32  TERMINAL O-S IN SULFONES AND SULFONAMIDES
  O3S    32  TERMINAL O IN SULFONATES
  O4S    32  TERMINAL O IN SO4(-3)
  OSMS   32  TERM O IN THIOSULFINATE ANION - FORMAL CHARGE=-0.5
  OP     32  TERMINAL O IN PHOSPHOXIDES
  O2P    32  TERMINAL O IN PHOSPHINATES
  O3P    32  TERMINAL OXYGEN IN PHOSPHONATES
  O4P    32  TERMINAL OXYGEN IN PHOSPHATES AND PHOSPHODIESTERS
  O4CL   32  OXYGEN IN CLO4(-) ANION - FORMAL CHARGE=-0.25
  HOS    33  H ON OXYGEN ATTACHED TO SULFUR
  NR+    34  QUATERNARY NITROGEN, SP3, POSITIVELY CHARGED
  OM     35  ALKOXIDE OXYGEN, NEGATIVELY CHARGED
  OM2    35  OXIDE OXYGEN ON SP2 CARBON, NEGATIVELY CHARGED
  HNR+   36  H ON QUATERNARY NITROGEN
  HIM+   36  H ON IMIDAZOLIUM-TYPE NITROGEN
  HPD+   36  H ON PROTONATED PYRIDINE NITROGEN
  HNN+   36  H ON AMIDINIUM-TYPE NITROGEN
  HNC+   36  H ON PROTONATED IMINE NITROGEN
  HGD+   36  H ON GUANIDINIUM-TYPE NITROGEN
  HN5+   36  H ON N5+, N5A+ OR N5B+
  CB     37  CARBON AS IN BENZENE, PYRROLE
  NPYD   38  NITROGEN, AS IN PYRIDINE
  NPYL   39  NITROGEN, AS IN PYRROLE
  NC=C   40  NITROGEN ON N-C=C
  NC=N   40  NITROGEN IN N-C=N
  NC=P   40  NITROGEN IN N-C=P
  NC%C   40  NITROGEN ATTACHED TO C-C TRIPLE BOND
  CO2M   41  CARBOXYLATE ANION CARBON
  CS2M   41  CARBON IN THIOCARBOXYLATE ANION
  NSP    42  NITROGEN, TRIPLE BONDED
  NSO2   43  NITROGEN IN SULFONAMIDES
  NSO3   43  NITROGEN IN SULFONAMIDES, THREE O'S ON S
  NPO2   43  NITROGEN IN PHOSPHONAMIDES
  NPO3   43  NITROGEN IN PHOSPHONAMIDES, THREE O'S ON P
  NC%N   43  NITROGEN ATTACHED TO CYANO GROUP
  STHI   44  SULFUR AS IN THIOPHENE
  NO2    45  NITRO GROUP NITROGEN
  NO3    45  NITRATE GROUP NITROGEN
  N=O    46  NITROSO NITROGEN
  NAZT   47  TERMINAL NITROGEN IN AZIDO OR DIAZO GROUP
  NSO    48  DIVALENT NITROGEN REPLACING MONOVALENT O IN SO2 GROUP
  O+     49  POSITIVELY CHARGED OXONIUM (TRICOORDINATE) OXYGEN
  HO+    50  HYDROGEN ON O+ OXYGEN
  O=+    51  POSITIVELY CHARGED OXENIUM (DICOORDINATE) OXYGEN
  HO=+   52  HYDROGEN ON OXENIUM OXYGEN
  =N=    53  NITROGEN IN C=N=N OR -N=N=N 
  N+=C   54  POSITIVELY CHARGED IMINIUM NITROGEN
  N+=N   54  POSITIVELY CHARGED NITROGEN DOUBLE-BONDED TO N
  NCN+   55  N IN +N=C-N RESONANCE STRUCTURES - FORMAL CHARGE=1/2
  NGD+   56  GUANIDINIUM-TYPE NITROGEN - FORMAL CHARGE=1/3
  CGD+   57  GUANIDINIUM CARBON
  CNN+   57  C IN +N=C-N RESONANCE STRUCTURES
  NPD+   58  PYRIDINIUM-TYPE NITROGEN - FORMAL CHARGE=1
  OFUR   59  AROMATIC OXYGEN AS IN FURAN
  C%     60  ISONITRILE CARBON
  NR%    61  ISONITRILE NITROGEN [FC = 0] OR DIAZO NITROGEN [FC = 1]
  NM     62  DEPROTONATED SULFONAMIDE N-; FORMAL CHARGE=-1
  C5A    63  ALPHA CARBON IN 5-MEMBERED HETEROAROMATIC RING
  C5B    64  BETA CARBON IN 5-MEMBERED HETEROAROMATIC RING
  N5A    65  ALPHA AROM HETEROCYCLIC 5-RING  NITROGEN
  N5B    66  BETA AROM HETEROCYCLIC 5-RING  NITROGEN
  N2OX   67  SP2-HYDRIDIZED N-OXIDE NITROGEN
  N3OX   68  SP3-HYDRIDIZED N-OXIDE NITROGEN
  NPOX   69  PYRIDINE N-OXIDE NITROGEN
  OH2    70  OXYGEN ON WATER
  HS     71  H ATTACHED TO DIVALENT, DICOORDINATE S
  HS=N   71  H ATTACHED TO TETRAVALENT, TRICOODR S DBL BONDED TO N
  HP     71  H ATTACHED TO TRI- OR TETRACOORDINATE PHOSPHORUS
  S-P    72  TERMINAL SULFUR BONDED TO PHOSPHORUS
  S2CM   72  TERMINAL SULFUR IN THIOCARBOXYLATE ANION
  SM     72  TERMINAL SULFUR - FORMAL CHARGE=-1
  SSMO   72  TERMINAL SULFUR IN THIOSULFINATE GROUP
  SO2M   73  SULFUR IN NEGATIVELY CHARGED SULFINATE GROUP
  SSOM   73  TRICOORD SULFUR IN THIOSULFINATE GROUP
  =S=O   74  SULFINYL SULFUR, EG. IN C=S=O
  -P=C   75  PHOSPHOROUS DOUBLY BONDED TO CARBON
  N5M    76  NEGATIVELY CHARGED N IN, E.G, TRI- OR TETRAZOLE ANION
  CLO4   77  CHLORINE IN PERCHLORATE ANION, CLO4(-)
  C5     78  GENERAL CARBON IN 5-MEMBERED HETEROAROMATIC RING
  N5     79  GENERAL NITROGEN IN 5-MEMBERED HETEROCYCLIC RING  
  CIM+   80  C IN N-C-N IN IMIDAZOLIUM ION
  NIM+   81  IMIDAZOLIUM-TYPE NITROGEN - FORMAL CHARGE=1/2
  N5A+   81  POSITIVE N5A NITROGEN - FORMAL CHARGE=1
  N5B+   81  POSITIVE N5B NITROGEN - FORMAL CHARGE=1
  N5+    81  POSITIVE N5 NITROGEN - FORMAL CHARGE=1
  N5AX   82  N-OXIDE NITROGEN IN 5-RING ALPHA POSITION
  N5BX   82  N-OXIDE NITROGEN IN 5-RING BETA POSITION
  N5OX   82  N-OXIDE NITROGEN IN GENERAL 5-RING POSITION
  FE+2   87  IRON +2 CATION
  FE+3   88  IROM +3 CATION
  F-     89  FLUORIDE ANION
  CL-    90  CHLORIDE ANION
  BR-    91  BROMIDE ANION
  LI+    92  LITHIUM CATION  
  NA+    93  SODIUM CATION
  K+     94  POTASSIUM CATION
  ZINC   95  DIPOSITIVE ZINC        
  ZN+2   95  DIPOSITIVE ZINC        
  CA+2   96  DIPOSITIVE CALCIUM     
  CU+1   97  MONOPOSITIVE COPPER    
  CU+2   98  DIPOSITIVE COPPER      
  MG+2   99  DIPOSITIVE MAGNESIUM CATION
