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β‐Sheet to Helical‐Sheet Evolution Induced by Topochemical Polymerization: Cross‐α‐Amyloid‐like Packing in a Pseudoprotein with Gly‐Phe‐Gly Repeats
Author(s) -
Hema Kuntrapakam,
Sureshan Kana M.
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201914975
Subject(s) - beta sheet , polymerization , crystallography , chemistry , hydrogen bond , azide , self assembly , peptide , stereochemistry , molecule , polymer , organic chemistry , biochemistry
Protein‐mimics are of great interest for their structure, stability, and properties. We are interested in the synthesis of protein‐mimics containing triazole linkages as peptide‐bond surrogate by topochemical azide‐alkyne cycloaddition (TAAC) polymerization of azide‐ and alkyne‐modified peptides. The rationally designed dipeptide N 3 ‐CH 2 CO‐Phe‐NHCH 2 CCH ( 1 ) crystallized in a parallel β‐sheet arrangement and are head‐to‐tail aligned in a direction perpendicular to the β‐sheet‐direction. Upon heating, crystals of 1 underwent single‐crystal‐to‐single‐crystal polymerization forming a triazole‐linked pseudoprotein with Gly‐Phe‐Gly repeats. During TAAC polymerization, the pseudoprotein evolved as helical chains. These helical chains are laterally assembled by backbone hydrogen bonding in a direction perpendicular to the helical axis to form helical sheets. This interesting helical‐sheet orientation in the crystal resembles the cross‐α‐amyloids, where α‐helices are arranged laterally as sheets.