The HELM project has developed a range of opensource tools which demonstrate what can be done with the notation.
HELM Web editor
Enables the user to create HELM strings by dragging and dropping monomers onto a sketchpad. Can interpret HELM strings or single letter sequences of natural monomers.
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HELM Antibody Editor (HAbE)
Originally developed by Roche for internal use, they kindly open-sourced it for the community in 2018.
The antibody editor uses a Blast search to identify domains. The editor displays the domains and can manipulate the structures, creating Cys-Cys bonds and make other edits very flexibly due to the underlying HELM notation.
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HELM Toolkit
A Java-based toolkit that creates webservices that can be accessed by third party tools.
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Search Tool
In 2017/18 Eva Bültel (Hamburg University supervised by quattro research) wrote her masters thesis on searching structures encoded in HELM.
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