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Molecular self-assembly provides a chemical strategy for the synthesis of nanostructures by using the principles of nature, and peptides serve as the promising building blocks to construct adaptable molecular architectures. Recently, a series of heptapeptides with alternative hydrophobic and hydrophilic residues were reported to form amyloid-like structures, which are capable of catalyzing acyl ester hydrolysis with remarkable efficiency. However, information remains elusive about the atomic structures of the fibrils. What is the origin of the sequence-dependent catalytic activity? How is the ester hydrolysis catalyzed by the fibrils? In this work, the atomic structures of the aggregates were determined by using molecular modeling and further validated by solid-state NMR experiments, where the fibril with high activity adopts twisted parallel configuration within each layer, and the one with low activity is in flat antiparallel configuration. The polymorphism originates from the interactions between different regions of the building block peptides, where the delicate balance between rigidity and flexibility plays an important role. We further show that the p-nitrophenylacetate ( pNPA) hydrolysis reactions catalyzed by two different fibrils follow a similar mechanism, and the difference in microenvironment at the active site between the natural enzyme and the present self-assembled fibrils should account for the discrepancy in catalytic activities. The present work provides understanding of the structure and function of self-assembled fibrils formed with short peptides at an atomic level and thus sheds new insight on designing aggregates with better functions.

Identifying the structure of electrodes at atomic-scale remains a key challenge but is a fertile realm for groundbreaking fundamental research in the advanced Li-ion battery material field. In this context, the subtle structure evolution taking place during lithiation/delithiation in the bulk/surface of Li(4)Ti(5)O(12) spinel (LTO) was probed using scanning transmission electron microscopy and found to undergo significant structure torque, namely Ti-O bond stretching/shrinking at different state-of-charge (SOC), which is not identified previously. This kind of nanostructure change plays an important role in facilitating the formation of capturing centers for the electron/hole pairs in a 3.80 eV insulating material as is LTO. Furthermore, with the aid of electron energy loss spectroscopy, the spontaneous charge transfer process, Ti(3+) ↔ e(-) + Ti(4+), was confirmed in the fully lithiated Li(7)Ti(5)O(12) surface as an essential step of the gas-releasing phenomenon. This new insight paves the way toward deeper comprehension and ultimately control of the electrochemical process for this and other important Li-ion battery materials.