Hi Mandar,

> On Dec 13, 2023, at 03:39, Mandar Kulkarni <mandar.kulkarni.c...@gmail.com> 
> wrote:
> I could not figure out how Rdkit is guessing it as 2D structure, as there is 
> no such information in SDF.

Line 2 of the SDF record looks something like:

     RDKit          2D

This line has the format (quoting from the documentation):

IIPPPPPPPPMMDDYYHHmmddSSssssssssssEEEEEEEEEEEERRRRRR 
A2<--A8--><---A10-->A2I2<--F10.5-><---F12.5--><-I6-> )

where "User's first and last initials (l), program name (P), date/time 
(M/D/Y,H:m), dimensional codes (d) such as 2D or 3D, scaling factors (S, s), 
energy (E) if modeling program input, internal registry number (R)"

In the example I gave, most of these fields are blank, except for the program 
name ("RDKit") and the dimension code "2D" in columns 21-22 (if I counted 
right). The dimension code indicates the structure is expected to be in 2D.

> Is there any more information need to provide SDMolSupplier to make it 
> understand it's a 3D molecule?

It is only a warning. RDKit interprets the molecule as 3D despite the warning.

The file format documentation also says: "The “dimensional code” is maintained 
explicitly. Thus “3D” really means 3D, although “2D” will be interpreted as 3D 
if any non-zero Z-coordinates are found.

Best regards,


                                Andrew
                                da...@dalkescientific.com




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