(T)orsion (A)ngular (B)in (S)trings

This release corresponds to the code used to generate the results of the publication (submitted, preprint below):
https://chemrxiv.org/engage/chemrxiv/article-details/66c8883aa4e53c48765c8a66

Abstract

Molecular flexibility is a commonly used, but not easily quantified term.
It is at the core of understanding composition and size of a conformational ensemble and contributes to many molecular properties.
For many computational workflows, it is necessary to reduce a conformational ensemble to meaningful representatives, however defining them and guaranteeing the ensemble's completeness is difficult.
We introduce the concepts of Torsion Angular Bin Strings (TABS) as a discrete vector representation of a conformer's dihedral angles and the number of possible TABS (nTABS) as an estimation for a molecule's ensemble size respectively.
Here we show that nTABS corresponds to an upper limit for the conformer space size for small molecules and compare the classification of conformer ensembles by TABS with classifications by RMSD.
Overcoming known drawbacks like the molecular size dependency and threshold picking of the RMSD measure, TABS is shown to meaningful discretize the conformer space and hence allows e.g. for fast conformer space coverage checks.
The current proof-of-concept implementation is based on the ETKDGv3sr conformer generator and known torsion preferences extracted from small-molecule crystallographic data.