Electrostatic Complementarity Drives Amyloid/Nucleic Acid Co‐Assembly

Cross β amyloid assemblies as complex catalytic machinery

How modern enzymes evolved as complex catalytic machineries to facilitate diverse chemical transformations is an open question for the emerging field of systems chemistry. Inspired by Nature's ingenuity in creating complex catalytic structures for exotic functions, short peptide-based cross β amyloid sequences have been shown to access intricate binding surfaces demonstrating the traits of extant enzymes and proteins. Based on their catalytic proficiencies reported recently, these amyloid assemblies have been argued as the earliest protein folds. Herein, we map out the recent progress made by our laboratory and other research groups that demonstrate the catalytic diversity of cross β amyloid assemblies. The important role of morphology and specific mutations in peptide sequences has been underpinned in this review. We have divided the feature article into different sections where examples from biology have been covered demonstrating the mechanism of extant biocatalysts and compared with recent works on cross β amyloid folds showing covalent catalysis, aldolase, hydrolase, peroxidase-like activities and complex cascade catalysis. Beyond equilibrium, we have extended our discussion towards transient catalytic amyloid phases mimicking the energy driven cytoskeleton polymerization. Finally, a future outlook has been provided on the way ahead for short peptide-based systems chemistry approaches that can lead to the development of robust catalytic networks with improved enzyme-like proficiencies and higher complexities. The discussed examples along with the rationale behind selecting specific amino acids sequence will benefit readers to design systems for achieving catalytic reactivity similar to natural complex enzymes.

Metal Complex Lipids for Fluid-Fluid Phase Separation in Coassembled Phospholipid Membranes

We demonstrate a fluid-fluid phase separation in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes using a metal complex lipid of type [Mn(L1)] (1; HL1=1-(2-hydroxybenzamide)-2-(2-hydroxy-3-formyl-5-hexadecyloxybenzylideneamino)ethane). Small amount of 1 produces two separated domains in DMPC, whose phase transition temperatures of lipids (T_c ) are both lower than that of the pristine DMPC. Variable temperature fluorescent microscopy for giant-unilamellar vesicles of DMPC/1 hybrids demonstrates that visible phase separations remain in fluid phases up to 37 °C, which is clearly over the T_c of DMPC. This provides a new dimension for the application of metal complex lipids toward controlling lipid distributions in fluid membranes.

Peak Force Infrared-Kelvin Probe Force Microscopy

Correlative scanning probe microscopy of chemical identity, surface potential, and mechanical properties provide insight into the structure-function relationships of nanomaterials. However, simultaneous measurement with comparable and high resolution is a challenge. We seamlessly integrated nanoscale photothermal infrared imaging with Coulomb force detection to form peak force infrared-Kelvin probe force microscopy (PFIR-KPFM), which enables simultaneous nanomapping of infrared absorption, surface potential, and mechanical properties with approximately 10 nm spatial resolution in a single-pass scan. MAPbBr₃ perovskite crystals of different degradation pathways were studied in situ. Nanoscale charge accumulations were observed in MAPbBr₃ near the boundary to PbBr₂ . PFIR-KPFM also revealed correlations between residual charges and secondary conformation in amyloid fibrils. PFIR-KPFM is applicable to other heterogeneous materials at the nanoscale for correlative multimodal characterizations.