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NextMove Software's Sugar & Splice.
This Sugar and Splice supports peptides along with DNA/RNA, inline HELM and XHELM [and IUPAC name generation, and depiction, and peptide name generation, and variable attachment points, and oligosaccharides etc.]. Further details can be found at https://www.nextmovesoftware.com/sugarnsplice.html
ChemAxon Biomolecule Toolkit
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