The characterization of the molecular structure and physical properties of self-assembling peptides is an important aspect of optimizing their utility as scaffolds for biomaterials and other applications. Here we report the formation of autofluorescent fibrils by an octapeptide (GVGVAGVG) derived via a single amino acid substitution in one of the hydrophobic repeat elements of human elastin. This is the shortest and most well-defined peptide so far reported to exhibit intrinsic fluorescence in the absence of a discrete fluorophore. Structural characterization by FTIR and solid-state NMR reveals a predominantly β-sheet conformation for the peptide in the fibrils, which are likely assembled in an amyloid-like cross-β structure. Investigation of dynamics and the effects of hydration on the peptide are consistent with a rigid, water excluded structure, which has implications for the likely mechanism of intrinsic fibril fluorescence.

Background: Nonfibrillar amyloid oligomers are cytotoxic and may act through physical disruption of cell membranes. Results: Cytotoxic oligomers of the amyloid peptide PrP(106 -126) disrupt membranes through distinct mechanisms, depending on lipid composition. Conclusion: Cytotoxicity of PrP(106 -126) oligomers can occur through at least two different physical processes. Significance: Mechanisms for the membrane disruption of amyloid oligomers are proposed, providing new insight into their cytotoxicity.

The formation of nonfibrillar oligomers has been proposed to be a common element of the aggregation pathway of amyloid peptides. Here we describe the first detailed investigation of the morphology and secondary structure of stable oligomers formed by a peptide comprising residues 106-126 of the human prion protein (PrP). These oligomers have an apparent hydrodynamic radius of approximately 30 nm and are more membrane-active than monomeric or fibrillar PrP(106-126). Circular dichroism and solid state NMR data support formation of an extended beta-strand by the hydrophobic core of PrP(106-126), while negative thioflavin-T binding implies an absence of cross-beta structure in nonfibrillar oligomers.

Amyloids are fibrillar protein superstructures that are commonly associated with diseases in humans and with physiological functions in various organisms. The precise mechanisms of amyloid formation remain to be elucidated. Surprisingly, we discovered that a bacterial Escherichia coli chaperone-like ATPase, regulatory ATPase variant A (RavA), and specifically the LARA domain in RavA, forms amyloids under acidic conditions at elevated temperatures. RavA is involved in modulating the proper assembly of membrane respiratory complexes. LARA contains an N-terminal loop region followed by a β-sandwich-like folded core. Several approaches, including nuclear magnetic resonance spectroscopy and molecular dynamics simulations, were used to determine the mechanism by which LARA switches to an amyloid state. These studies revealed that the folded core of LARA is amyloidogenic and is protected by its N-terminal loop. At low pH and high temperatures, the interaction of the N-terminal loop with the folded core is disrupted, leading to amyloid formation.

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Herein, we propose a high-quality (Q) factor hybrid plasmonic nanocavity based on distributed Bragg reflectors (DBRs) with low propagation loss and extremely strong mode confinement. This hybrid plasmonic nanocavity is composed of a high-index cylindrical nanowire separated from a metal surface possessing shallow DBRs gratings by a sufficiently thin low-index dielectric layer. The hybrid plasmonic nanocavity possesses advantages such as a high Purcell factor (F p) of up to nearly 20000 and a gain threshold approaching 266 cm−1 at 1550 nm, promising a greater potential in deep sub-wavelength lasing applications.

cells. Using surface plasmon resonance and centrifugation assays, we have found that the Smurf1 C2 domain binds to phosphoinositides and phosphatidylserine in an synergistic fashion. Confocal images of Smurf1 C2-GFP demonstrate that the domain localizes to the plasma membrane as well as intracellular vesicles in cells. Site-directed mutagenesis has shown the specific residues in the loop region of the protein involved in its cellular membrane localization. In addition, we have used a rapamycin-inducible phosphoinositide phosphatase system to demonstrate that this domain binds phosphoinositides at the plasma membrane. We conclude that the unique properties of the Smurf1 C2 domain to sense specific lipids in addition to anionic charge enable it to target multiple subcellular locations.