Single Fluorescent Peptide Nanodots

Abstract

Fluorescent peptide nanodots (PNDs) are bioorganic nanoparticles self-assembled from peptide biomolecules of different origin and complexity. These recently discovered nanodots of biological origin are highly promising for biomedical imaging applications due to their biocompatibility, bright and tunable fluorescence over the entire visible range and photostability. Here we apply single-particle microscopy methods to study the photophysical properties of individual PNDs. We show that the fluorescence spectrum tunability, studied previously only for PND ensembles in solutions, origins at the single-particle level. Temporal dynamics measurements of the single particles reveal fluorescence lifetime in the range of nanoseconds and pronounced fluorescence blinking with continuous bright states of seconds. The latter provides a first evidence of quantum emitter transitions between two states (ON and OFF) in fluorescent PNDs. All these findings advance the understanding of the fluorescence mechanism of PNDs and provide strong motivation for using PNDs as fluorescent agents for various bioimaging and super-resolution techniques.

Long‐Range Fluorescence Propagation in Amyloidogenic β‐Sheet Films and Fibers

“…The amyloidogenic structures under study exhibit exclusive broadband, fully overlapped FL and OA spectra (Figure 1 and 3), which are created by the electronic structure of noncovalent hydrogen bonds responsible for visible FL in amyloid structures. [ 9–12,14–17 ] FL and OA effects are detected along the entire visible spectrum in the 400–650 nm range. This effect provides the observation of any FL visible color, blue, green, yellow, red, and more.…”

“…This intrinsic, structure‐sensitive bio‐effect has been observed in a variety of β‐sheet disease‐related human peptide amyloid fibrils, [ 10,11 ] native silk fibrils, [ 12 ] synthetic vapor‐deposited diphenylalanine (FF)‐fibers, [ 13 ] bioinspired thermally refolded diaromatic and triaromatic and aliphatic peptide nanostructures, [ 9,14 ] and recently in peptide/protein nanodots. [ 15,16 ] Regardless of their composition and origin, they irradiate FL in a similar visible range within a wide spectral maximum in the blue region. Recently, a deep study of amyloid fibrils involving 13 different amyloid proteins showed that, in addition to its blue component, the amyloid FL signal also contains a red near‐infrared FL spectral component with wavelengths of 780–820 nm.…”

“…The latter folds into a peptide β‐sheet structure and exhibits a new phenomenon of quasi‐white visible FL, in which PEG‐polymer chains contribute to wideband green FL [ 43–45 ] in addition to the blue FL found in diverse beta‐sheet disease‐related human peptide/protein amyloid fibrils, native silk fibrils, vapor‐deposited diphenylalanine fibers, and recently in peptide/protein nanodots. [ 9–17 ] The PEG‐6 peptide films have a very large area, making these unique peptide films promising for complex peptide integrated photonic devices. We demonstrate in these films effective optical passive FL waveguiding in fabricated simple photonic circuits.…”

Fluorescence Phenomena in Amyloid and Amyloidogenic Bionanostructures

“…In the bioinspired materials, we observed similar fibrillary structures grown under the thermally induced transformation of the native helix-like state to the β-sheet one. These β-sheet amyloidogenic fibers deeply change original non-fluorescent optical properties and lead to the appearance in the β-sheet state of a new fold-sensitive effect of visible FL phenomenon in the region~400-700 nm [2,3,[89][90][91][92][93]. Figure 10 accumulates basic experimental data on the helix-like→β-sheet transition and FL phenomena in bioinspired materials.…”

“…All of them displayed visible FL effects, which were ascribed to electron delocalization caused by hydrogen bonds in the β-sheet structure, providing low energy electronic transitions. Later, this new and unusual visible FL was disclosed in two different large classes of amyloid [1,[85][86][87][88] and amyloidogenic [2,3,[89][90][91][92][93] peptide/protein structures as well as in a new generation of hybrid polymer/peptide thin films and fiber materials [94,95]. All of them were folded into a β-sheet secondary structure.…”