Selected peptide-based fluorescent probes for biological applications

Abstract

To understand the molecular interactions, present in living organisms and their environments, chemists are trying to create novel chemical tools. In this regard, peptide-based fluorescence techniques have attracted immense interest. Synthetic peptide-based fluorescent probes are advantageous over protein-based sensors, since they are synthetically accessible, more stable, and can be easily modified in a site-specific manner for selective biological applications. Peptide receptors labeled with environmentally sensitive/FRET fluorophores have allowed direct detection/monitoring of biomolecules in aqueous media and in live cells. In this review, key peptide-based approaches for different biological applications are presented.

Keywords: fluorescent probe; fluorophores; molecular recognition; peptide-based.

Figure 1

Three different type of peptide-based fluorescent probes and their interaction with nucleic acids are shown. A) Environment-sensitive fluorophore attached peptide shows “switch-on” fluorescence response upon interaction with nucleic acids. Reproduced with permission from [32], Maity et al., “Peptide‐Based Probes with an Artificial Anion‐Binding Motif for Direct Fluorescence “Switch‐On” Detection of Nucleic Acid in Cells”, Chem. – Eur. J. © 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim; B) FRET pair attached peptide shows ratiometric fluorescence response upon interaction with nucleic acids. Reproduced from [33] with permission from The Royal Society of Chemistry; C) a pyrene-attached peptides shows ratiometric fluorescence response upon interaction with nucleic acids. Reprinted with permission from [34]. Copyright (2012) American Chemical Society.

Figure 2

A) Molecular structure of peptidic probe 1, Inset: HeLa cells incubated with peptide 1 (50 μM), showing an ATP responsive green fluorescence; B) fluorescence emission spectra of probe 1 (20.0 µM) (λ_ex = 410 nm) with increasing concentration (0–10.0 µM) of ATP in 10 mM HEPES buffer, pH 7.4. Reproduced from [39] with permission from The Royal Society of Chemistry.

Figure 3

A) Molecular structure of probe 2; B) fluorescence emission spectra for the titration of a 10 μM solution of 2 with p(dA·dT)₂ in aqueous buffer (pH 7.4) (with base pair/2 molar ratios ranging from 0 to 4.0), inset: nuclei of HeLa cells stained with 2. Reprinted with permission from [34]. Copyright (2012) American Chemical Society.

Figure 4

A) Molecular structure of 3; B) fluorescence emission spectra for the titration of a 10 μM solution of 3 with p(dA·dT)₂ in 10 mM HEPES buffer (pH 7.4) (with base pair/3 molar ratios ranging from 0 to 5.0), inset: Nuclei of A549 cells stained with 3. Reproduced from [33] with permission from The Royal Society of Chemistry.

Figure 5

A) Molecular structure of 4 and 5; B) fluorescence spectra for the titration of a 0.5 μM solution of 4 with increasing concentration of p(dA·dT)₂ (λ_ex = 410 nm). Inset: fluorescence switched-on after addition of dsDNA inside the cuvette, nuclei of A549 cells stained with 4. Reproduced with permission from [32], Maity et al., “Peptide‐Based Probes with an Artificial Anion‐Binding Motif for Direct Fluorescence “Switch‐On” Detection of Nucleic Acid in Cells”, Chem. – Eur. J. © 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim.

Figure 6

A) Molecular structure of 6; B) possible binding mode of pyrene termini of 6 to CB[8] according to molecular modeling; C) cartoon representation of ratiometric fluorescent detection application using 6 and the CB[8] conjugate. (The photographs show the corresponding cuvettes under UV light). Reproduced from [42], © 2019 Maity et al., distributed under the terms of the Creative Commons Attribution 4.0 International Licence, http://creativecommons.org/licenses/by/4.0/.

Figure 7

A) Molecular structure of peptidic probes 7 and 8; B) fluorescence emission spectra of probe 7 (5.0 µM) with increasing concentration (0–5.0 µM) of 14-3-3β protein (λ_ex = 410 nm). Inset: Corresponding fluorescence color of the solution inside cuvette under UV lamp. Reproduced from [47] with permission from The Royal Society of Chemistry.

Figure 8

Top: Molecular structure of 9; bottom: A) fluorescence response of 9 (500 nM) upon addition of β-tryptase (0–20 nM). Inset: the corresponding titration curve showing the increase of the emission at 400 nm with increasing β-tryptase concentration; B) confocal laser scanning microscopy images of CHMAS cells treated with 10 μM peptide 9 for 30 min. Reproduced from [51], “A fluorescent light-up probe as an inhibitor of intracellular β-tryptase”, © 2014 Wang et al., licensed under a Creative Commons Attribution 3.0 Unported Licence, https://creativecommons.org/licenses/by/3.0/. Published by The Royal Society of Chemistry.

Figure 9

Top: Molecular structures of 10 and 11; bottom: A) fluorescence emission spectra of 10 (1.0 µM, λ_ex = 340 nm); B) fluorescence emission spectra 11 (1.0 µM, λ_ex = 270 nm) with increasing concentration of heparin. Reproduced with permission from [56], Maity, D.; and Schmuck, C., “Fluorescent peptide beacons for the selective ratiometric detection of heparin”, Chem. – Eur. J. © 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim.

Figure 10

A) Structure of two peptide amphiphiles 12 and 13; B) fluorescent spectra (λ_ex = 400 nm) from a titration of the PDA liposomes (molar ratio 12/13 = 1:9, total monomer concentration = 10.0 μM, 25 °C) in 10.0 mM DMSO/TBS (v/v = 1:4, pH 7.4). The insets show the normalized fluorescence intensity at 515 nm vs the concentration of LPS (0–3.6 μM) and the fluorescence turn-on; C) confocal luminescence image for E. coli DH5α after incubation with the PDA liposomes. Reprinted with permission from [59]. Copyright (2011) American Chemical Society.

Figure 11

a) Molecular structure of peptide 14; b) the coordinate represents the states of sensor at different pH values, purple sphere: protonated merocyanine (McH⁺), red sphere: normal merocyanine (Mc), and gray sphere: spiropyran at a ring-closed state (Sp); colocalization experiments using peptide 14, LysoTracker Green DND-26 (LTG) and Hoechst 33258 in A549 cells. Cells were stained with c) 10 µM peptide 14 (channel 1: excitation: 515 nm, emission collected: 600–650 nm), d) 0.1 µM LTG (channel 2: excitation: 488 nm, emission collected: 500–550 nm) and e) 10 µg/mL Hoechst 33258 (channel 3: excitation: 405 nm, emission collected: 420–470 nm). Reproduced from [64], “A switchable peptide sensor for real-time lysosomal tracking”, © 2014 Chen et al., licensed under a Creative Commons Attribution 3.0 Unported Licence, https://creativecommons.org/licenses/by/3.0/. Published by The Royal Society of Chemistry.