Amyloid Aggregates Arise from Amino Acid Condensations under Prebiotic Conditions

Current theories on the origin of life reveal significant gaps in our understanding of the mechanisms that allowed simple chemical precursors to coalesce into the complex polymers that are needed to sustain life. The volcanic gas carbonyl sulfide (COS) is known to catalyze the condensation of amino acids under aqueous conditions, but the reported di‐, tri‐, and tetra‐peptides are too short to support a regular tertiary structure. Here, we demonstrate that alanine and valine, two of the proteinogenic amino acids believed to have been among the most abundant on a prebiotic earth, can polymerize into peptides and subsequently assemble into ordered amyloid fibers comprising a cross‐β‐sheet quaternary structure following COS‐activated continuous polymerization of as little as 1 mm amino acid. Furthermore, this spontaneous assembly is not limited to pure amino acids, since mixtures of glycine, alanine, aspartate, and valine yield similar structures.Once upon a time: The aqueous synthesis of peptides under conditions that are relevant to a prebiotic earth leads to the formation of ordered amyloid aggregates. With mixtures of four amino acids, such conditions yield thousands of unique peptides that then undergo a spontaneous selection and self‐assembly process. The inherent ability of simple peptides to form ordered quaternary structures may be relevant to the origins of biological macromolecules.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137528/1/anie201605321_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137528/2/anie201605321.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137528/3/anie201605321-sup-0001-misc_information.pd

Thermosensitive Nanocables Prepared by Surface-Initiated Atom Transfer Radical Polymerization

Thermosensitive nanocables consisting of Au nanowire cores and poly(N-isopropylacrylamide) sheaths (denoted as Au/PNIPAAm) were synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP). The formation of PNIPAAm sheath was verified by Fourier transform infrared (FTIR) and hydrogen nuclear magnetic resonance (1H NMR) spectroscopy. Transmission electron microscope (TEM) results confirmed the core/shell structure of nanohybrids. The thickness and density of PNIPAAm sheaths can be adjusted by controlling the amount of cross-linker during the polymerization. Signature temperature response was observed from Au/cross-linked-PNIPAAm nanocables. Such smart nanocables show immense potentials as building blocks for novel thermosensitive nanodevices in future

Synthesis of Amides and Esters by Palladium(0)-Catalyzed Carbonylative C(sp3)-H Activation

The 1,4-palladium shift strategy allows the functionalization of remote C-H bonds that are difficult to reach directly. Reported here is a domino reaction proceeding by C(sp3)-H activation, 1,4-palladium shift, and amino- or alkoxycarbonylation, which generates a variety of amides and esters bearing a quaternary beta-carbon atom. Mechanistic studies showed that the aminocarbonylation of the sigma-alkylpalladium intermediate arising from the palladium shift is fast using PPh3 as the ligand, and leads to the amide rather than the previously reported indanone product

Fabrication of Coaxial Metal Nanocables Using a Self-Assembled Peptide Nanotube Scaffold

The design and fabrication of complex nanostructures with specific geometry and composition is one of the main challenges of nanotechnology. Here we demonstrate the devise of metal−insulator−metal, trilayered, coaxial nanocables. Such coaxial geometry may give rise to useful and unique electromagnetic properties. We have fabricated these nanostructures using a scaffold of self-assembled peptide nanotubes. Gold nanoparticles were bound to the surface of peptide nanotubes via a common molecular recognition element that was included in various linker peptides. This enabled us to promote site-specific metal reduction and to create the coaxial nanostructure. Using electron microscopy, 1H NMR spectra, and energy-dispersive X-ray analysis, we monitored the different steps within the process, gaining further understanding of its mechanism