Design, Synthesis, and Properties of a Chemically Tethered Amyloid-β Segment Trimer Resistant to Intertrimer Mis-aggregation

The oligomer species of amyloid-β peptide (Aβ) may be relevant to the development of Alzheimer’s disease. Isolating specific oligomer species of Aβ (i.e., dimers, trimers, tetramers, etc.), however, is difficult due to the transient, labile property of the oligomers. Here, we improved the resistance to intertrimer mis-aggregation of chemically tethered Aβ 25–35 trimers by introducing charged structures to the cyclic peptide tether that is covalently attached to the Aβ chain. The resistance to aggregation of the chemically tethered trimers positively correlated with the number of negative charges at the tether. Thus, a chemical trimer possessing three malonic acids at the tether exhibited high resistance because of the attenuated self-association by anionic repulsion. In addition, the malonic acid trimer possessed amyloidogenic properties such as cross-β-sheet structures, seeding activity, and cytotoxicity. This is the first study demonstrating that chemical modifications at the non-Aβ component enhance the resistance to aggregation of chemically tethered Aβ oligomers, by which the structural integrity of Aβ is maintained. Biological/biophysical evaluations of the intertrimer aggregation-resistant trimer may offer new, useful insights into the pathological functions of Aβ oligomers.