The FORMUL record presents the chemical formula and charge of a non-standard group. (The formulas for the standard residues are given in Appendix 5.)

Record Format

 1 -  6        Record name     "FORMUL"

 9 - 10        Integer         compNum        Component number.

13 - 15        LString(3)      hetID          Het identifier.

17 - 18        Integer         continuation   Continuation number.

19             Character       asterisk       "*" for water.

20 - 70        String          text           Chemical formula.


* The elements of the chemical formula are given in the order C, H, N, and O, with other elements following in alphabetical order, each separated by a single blank.

* The number of each atom type present immediately follows its chemical symbol with no intervening blank.

* Each set of SEQRES records and each HET group is assigned a component number in an entry. These numbers are assigned serially, beginning with 1 for the first set of SEQRES records. In addition:

- If a HET group is presented on a SEQRES record its FORMUL is assigned the component number of the chain in which it appears.
- If the HET group occurs more than once and is not presented on SEQRES records, the component number of its first occurrence is used.

* All occurrences of the HET group within a chain are grouped together with a multiplier. The remaining occurrences are also grouped with a multiplier. The sum of the multipliers is the number equaling the number of times that that HET group appears in the entry.

* The "*" in column 19 is used if the HET group is water or UNX, indicating that it should be excluded from the molecular weight calculation.

* A continuation field is provided in the event that more space is needed for the formula. Columns 17 - 18 are used in order to maintain continuity with the existing format.

Verification/Validation/Value Authority Control

For each het group that appears in the entry, the corresponding HET, HETNAM, FORMUL, HETATM, and CONECT records must appear. The FORMUL record is generated automatically by PDB processing programs using the het group template file and information from HETATM records.

Relationships to Other Record Types

For each het group that appears in the entry, the corresponding HET, HETNAM, FORMUL, HETATM, and CONECT records must appear.


         1         2         3         4         5         6         7
FORMUL   2  SO4    2(O4 S1 2-)
FORMUL   3  GLC    C6 H12 O6

FORMUL   3  FOL    2(C19 H17 N7 O6 2-)
FORMUL   4   CL    2(CL1 1-)
FORMUL   5   CA    CA1 2+
FORMUL   6  HOH   *429(H2 O1)

FORMUL   3  UNX   *3(X1)
FORMUL   4  HOH   *256(H2 O1)

FORMUL   1  ACE    C2 H3 O1
FORMUL   2  ACE    C2 H3 O1

Known Problems

Partially deuterated centers are not well represented in this record.