The Hierarchical Editing Language for Macromols. (HELM) is an open biomol. representation standard that provides a means to represent multiple types of complex macromols. (e.g. nucleotides, proteins, antibodies and antibody-drug conjugates) including those that contain non-natural elements.Oligonucleotides are seeing more and more use in research and as a therapeutic drug.Their variability can be increased heavily by using non-natural elements.However, the biol. effect is biased towards elements with a similarity to a natural analog.A new algorithm that allows users to establish a similarity measure between arbitrarily complex biomols. was recently developed by quattro research.Based on the calculation of fingerprints from HELM notations, we analyzed the similarity of oligonucleotides in comparison to their chem. similarity.The HELM similarity library can analyze complex polymers and nucleotides with non-natural elements.This is an outstanding feature in comparison to sequence-based tools.