Cross‐β Amyloid Nanohybrids Loaded With Cytochrome C Exhibit Superactivity in Organic Solvents

Abstract

The present study reports the development of a unique class of Cytochrome C (CytC)-loaded cross-beta amyloid nanohybrids. The peroxidase activity of the bound CytC increased up to two orders of magnitude in organic solvents compared to the activity of unbound CytC in water. The amyloid sequences used in the study feature the nucleating core (17) LVFF(21) of the beta amyloid (Aβ), which assembled to form homogenous fibers and nanotubes. The morphology and exposed surface of the amyloid nanohydrids critically modulated the CytC activity. A CytC-Ac-KLVFFAE-NH2 hybrid featuring nanofiber morphology showed 308-fold higher activity than unbound CytC in water, which increased to 450-fold with the nanotube morphology of CytC-Ac-KLVFFAL-NH2 . Notably, activity declined substantially when the exposed surface charge was detuned by replacing lysine with histidine, thus underpinning the importance of surface charge. This enzyme-amyloid nanohybrid system could facilitate the technological application of enzymes.

Efficient MoS2 Exfoliation by Cross‐β‐Amyloid Nanotubes for Multistimuli‐Responsive and Biodegradable Aqueous Dispersions

“…Nanotube morphology was found to be better for MoS 2 exfoliation as the amount of dispersed MoS 2 increased to 0.16 mg mL −1 . To remove the effect of pH, a glutamic acid residue was changed to leucine to form Ac‐KLVFFAL‐NH 2 , which at neutral pH assembled to form homogenous nanotubes with diameters of 35–40 nm (Figure E) ,. The amount of dispersed MoS 2 increased further with Ac‐KLVFFAL‐NH 2 nanotubes to 0.18 mg mL −1 .…”

“…To check the capability of amyloid nanostructures for MoS 2 exfoliation, we started with Ac‐KLVFFAE‐NH 2 from 16–22 residues of wildtype Aβ . Ac‐KLVFFAE‐NH 2 assembles to form classical amyloid fibrils with lengths of several microns and diameters of approximately 15 nm (Supporting Information, Figure S1).…”

“…TGA showed the MoS 2 residue was devoid of any bound peptides (Figure S9), and thus indicated the absence of any covalent interactions with the MoS 2 sheets. In this context, owing to the antiparallel out‐of‐register arrangement of β‐amyloid 17 LVFFA 21 sequences,,, leucine residues generate hydrophobic regions on the nanotube surface, which presumably interact with the MoS 2 nanosheets through weak physical adsorption. The dual presence of hydrophobic regions and charged lysine residues on the amyloid surface has been shown to bind hydrophobic moieties of small molecules, hydrophobic 2D graphene sheets,, and also hydrophobic patches of cationic proteins .…”

“…In addition to the charge, the colloidal stability of peptide nanotubes is expected to play a crucial role in the exfoliation. To investigate this, sodium sulfate was used to counterbalance the electrostatic repulsion of Ac‐KLVFFAL‐NH 2 nanotubes, as divalent sulfate ions are known to precipitate proteins and bundle amyloid nanotubes . Indeed, TEM confirmed bundling (Figure C) with addition of SO 4 2− ions, and the bundled tubes were unable to exfoliate MoS 2 (Figure A; Supporting Information).…”

Efficient MoS2 Exfoliation by Cross‐β‐Amyloid Nanotubes for Multistimuli‐Responsive and Biodegradable Aqueous Dispersions

“…Atomic force microscopy (AFM) also showed shorter nanotubes ( Figure 1H). To confirm that the surface of the short nano- (1)A c-KLVFFAE-NH 2 nanotubes at pH 2(2), Ac-KLVFFAL-NH 2 nanotubes ( 3), Ac-HLVFFAL-NH 2 nanotubesatpH6.5 (4)and at pH 9 (5), sodium cholate (6), bundled Ac-KLVFFAL-NH 2 nanotubes ( 7), and lysine (8). B) Typical UV/Vis absorption spectra of exfoliated MoS 2 in Ac-KLVFFAE-NH 2 nanofibers (1), Ac-KLVFFAE-NH 2 nanotubes(2), Ac-KLVFFAL-NH 2 nanotubes ( 3), Ac-HLVFFAL-NH 2 nanotubesatpH6.5 (4).…”