Chameleonic Dye Adapts to Various Environments Shining on

Subscriber access provided by UNIVERSITY OF CONNECTICUT

Article

A chameleonic dye adapts to various environments shining on macrocycles or peptide and polysaccharide aggregates. Hang Yin, Frédéric Dumur, Yiming Niu, Mehmet Menaf Ayhan, Olivier Grauby, Wei Liu, Chunming Wang, Didier Siri, Roselyne Rosas, Alain Tonetto, Didier Gigmes, Ruibing Wang, David Bardelang, and Olivier Ouari ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b06634 • Publication Date (Web): 31 Aug 2017 Downloaded from http://pubs.acs.org on September 2, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 12

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

TOC graphic 372x126mm (150 x 150 DPI)

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 12

A chameleonic dye adapts to various environments shining on macrocycles or peptide and polysaccharide aggregates. Hang Yin,1 Frederic Dumur,2 Yiming Niu,1 Mehmet M. Ayhan,2,3 Olivier Grauby,4 Wei Liu,1 Chunming Wang,1 Didier Siri,2 Roselyne Rosas,5 Alain Tonetto,6 Didier Gigmes,2 Ruibing Wang,1* David Bardelang,2* Olivier Ouari2* 1

State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of 2 3 Macau Avenida da Universidade, Taipa, Macau, China. Aix Marseille Univ, CNRS, ICR, Marseille, France. De4 partment of Chemistry, Gebze Technical University, P.K.:141, 41400 Gebze, Kocaeli, Turkey. Aix Marseille Univ and 5 CINaM, Campus de Luminy, Marseille, France. Aix Marseille Univ, CNRS, Spectropole, FR 1739, Marseille, France. 6 Aix Marseille Univ, Centrale Marseille, CNRS, Fédération Sciences Chimiques Marseille (FR 1739) - PRATIM, 13331 Marseille, France. ABSTRACT: This work describes Latent Fluorescence Particles (LFPs) based on a new environment sensitive carbazole compound aggregated in water, and their use as sensors for probing various cavitands and the different stages of aggregating systems. Cyclodextrins (CDs), cucurbit[n]urils (CB[n], n = 6, 7, 8) and a resorcinarene capsule were used to study the dynamic nature of the LFPs. The fluorescence was dramatically enhanced by a proposed Disaggregation Induced Emission Enhancement (DIEE) mechanism with specific features for CB[n]. Then, the aggregated states of the dipeptides Leu-Leu, Phe-Phe and Fmoc-Leu-Leu (vesicles, crystals, fibers) were studied by fluorescence spectroscopy and confocal fluorescence microscopy thanks to the adaptive and emissive behavior of the LFPs allowing to study an interesting polymorphism phenomenon. The LFPs have then been used to the sensing of the aggregation of the polysaccharide alginate, for which distinct fluorescence turn-on is detected upon stepwise biopolymer assembly, and for amylose detection. The carbazole particles not only adapt to various environments but also display multicolor fluorescent signals. They can be used for the fast probing of the aggregation propensity of newly prepared molecules or biologically relevant compounds, or to accelerate the discovery of new macrocycles or of self-assembling peptides in water.

INTRODUCTION Beyond the specialized meaning of a “chameleon effect” in social sciences1 and physical sciences,2 chameleon effects have also been described in chemistry. A chemical definition could tentatively be given as “a compound modifying its color in response to environmental changes”, so as chameleons do in a similar fashion. For chameleons yet, the mechanism for their skin color adaptation has been assigned to a dispersion-aggregation of pigment loaded organelles in dermal chromatophores but recent findings point to the active role of a tunable guanine nanocrystals lattice in dermal iridophores.3 Several chemical instances have reported “chameleon effects” assigned to (i) pH variations,4 (ii) chemical ligation,5-7 (iii) the various arrangements within a dye aggregate,8 (iv) multiple emission fluorophores with9,10 or without11,12 ratiometric

emission, and (v) environment-sensitive fluorescent probes.13-16 With cucurbituril macrocycles,17-19 we fortuitously discovered that a stylbazolium dye (Figure 1), spontaneously aggregated in water in the form of profluorescent particles, can disaggregate in the presence of various macrocycles resulting in bright emissions. These dynamic particles have been used in several other instances for the instant characterization of the presence of macrocycles in water or for probing the aggregation propensity of several self-assembling systems tracked by large fluorescence turn-on. The dynamic Latent Fluorescence Particles (LFPs) not only adapt to various surroundings but also change the emitted color as a function of the environment revealing the various shapes of self-assembled compounds in water such as vesicles, fibers, or crystals.

1 ACS Paragon Plus Environment

Page 3 of 12

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1. Molecular structure of the stylbazolium compound (Latent Fluorescence Dye LFD-01) and principle of Latent Fluorescence Particles (LFPs) for sensing by fluorescence recovery upon subsequent binding events.

The purpose of this work was not to use the described LFPs for biological imaging but rather use them as convenient probes for the rapid (instant) assessment of the presence of macrocycles in aqueous solutions with a (selective) output fluorescence signal and to rapidly estimate the aggregation propensity of several compounds in water that could have relevance for in vitro biology (i. e. amyloid peptides) or materials science (i. e. peptide materials, alginate gels). Compared to other environment sensitive probes20-23 with similar Disassembly-Induced Emission Enhancement (DIEE),24-28 the described LFPs have shown a high versatility in characterizing several macrocycles (cyclodextrins, cucurbiturils, etc …) and polymorphous self-assemblies (peptides organized as vesicles, fibers and crystals, and also polysaccharides as spheres and fibers). Extensive use of NMR, UV, fluorescence, DLS, SEM, TEM, mass spectrometry, modeling, and confocal fluorescence microscopy allowed characterizing the DIEE processes. It allowed (i) quickly finding which compounds have a chance to aggregate (instant monitoring by fluorescence turn-on) and (ii) characterizing new morphologies of dipeptide and polysaccharide aggregates (confocal microscopy). The design of the dye combined the hydrophobic features of (i) a fatty hydrocarbon tail, (ii) a cationic hydrophobic pyridinium moiety attached on (iii) a fluorescent carbazole core. This structure allows for multiple recognition events, self-assembled or not, to be monitored by the recovery of the latent stylbazolium fluorescence.

RESULTS AND DISCUSSION Synthesis and solvent study. LFD-01 has been prepared in a two-step sequence and all details and characterizations are given in Supporting Information (Figures S1 to S14). LFD-01 is soluble in several organic solvents such as dichloromethane, ethanol, DMSO and acetonitrile, but is poorly soluble in water. It shows a rather moderate solvatochromism (except in dichloromethane, see Fig. 2a). In water however, the absorption is less intense and blueshifted (hypsochromic shift ≈ 10 nm) that is generally assigned to the formation of H-aggregates29,30 presumably driven by aromatic stacking and hydrophobic effects.

Figure 2. Solvent study of LFD-01. (a) UV-visible spectra and -6 (b) photoluminescence spectra of LFD-01 (2.8×10 M and -5 8.3×10 M respectively) in organic solvents and in water. Note the large quenched emission of LFD-01 in water (inset photo under UV).

This aggregation phenomenon is confirmed by the strongly quenched emission of LFD-01 in water displaying an absolute fluorescence quantum yield (Φf) of 0.021 (see Fig. 2b inset) as compared to dichloromethane and DMF solutions where it shows a yellow emission at 593 nm with Φf = 0.134 and 0.376 respectively (see Table S1) with no sign of aggregation as monitored by DLS (see Figures S15). The emission peak in water is also broader than in organic solvents and ≈ 20 nm blue-shifted to 572 nm. Water: Latent Fluorescence Particles (LFPs). To explain the results observed in water, we wondered about a possible amphiphilic nature of LFD-01. Modeling of the electrostatic potential surface is in agreement with a polar section for the pyridinium moiety and a hydrophobic domain for the carbazole core and the octyl chain (see Fig. 3a). Optical microscopic observations of LFD-01 (100 µM, 2 minutes ultrasound) in water showed the presence of small and large particles (40×, µm range). Dynamic Light Scattering (DLS) of LFD-01 vortexed in water for 60 seconds (after filtration, see Fig. 3b) showed a peak corresponding to nanoparticles in the 30-400 nm range that agree reasonably well with Scanning Electron Microscopy (SEM, see Fig. 3c) that indicated the presence of both micro- and nanoparticles.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 12

Figure 3. Aggregation behavior of LFD-01. (a) Electrostatic potential surface on the structure of LFD-01, (b) Dynamic Light Scattering, (c) Scanning Electron Microscopy and (d) Transmission Electron Microscopy of LFP-01 (100 µM) in water.

Transmission Electron Microscopy (TEM, see Fig. 3d) showed microparticles and nanoparticles of 5-10 nm that are further assembled into aggregates of dimensions ≈ 20200 nm.31 Samples exposed to ultrasound for 2 minutes produce slightly larger particles as determined by DLS (see Figure s18) and TEM (see Figure S19). Therefore, the intrinsic fluorescence of LFD-01 almost vanished in water (λem = 572 nm, Φf = 0.021) with the simultaneous formation of Latent Fluorescence Particles LFP-01. We also noted a further aggregation with time leading to LFPs precipitation (presumably microparticles, shoulder of Fig. 3b) and for the studies described below, we used freshly made solutions to limit this further process. To establish the accessibility or the dynamic/reversible nature of LFP01 particles, we sought for suitable binders that could either (i) bind to the surface of the particles or (ii) trigger the particle disassembly. For this purpose, the synthetic macrocycles cucurbit[n]urils (CB[n])17-19 appeared ideally suited due to their well-established propensity to complex pyridinium32 and alkyl moieties33 with good affinities (Ka ≈ 104-5 M-1). CB[n] as probes for DIEE. Cucurbit[n]urils (CB[n]) are synthetic macrocycles that are increasingly investigated because of their outstanding properties such as ultrahigh affinity,34,35 drug binding36-38 or supramolecular clicking3941 of suitably functionalized molecules. Among these fascinating compounds, CB[6], CB[7] and CB[8] have been reported to modify charge transfer or fluorescence properties of relevant molecules after inclusion complexation in their hydrophobic cavities.

Figure 4. CB[7] binding. (a) UV-visible and (b) Photoluminescence (PL) spectra of LFD-01 in the presence of CB[7] ([LFD-01] = 10 µM, room temperature, titrated with CB[7] from 0 to 120 µM).

Cucurbiturils can exert strong effects on the fluorescence of encapsulated guests for example due to the low polarizability of their cavities42 or dramatically impact the fluorescence lifetimes or the quantum yields upon binding.43 These features significantly impact the fluorescence emission of the CB[n] complexes with fluorescence increases commonly reaching between 20 and 50 times and in few cases up to two or three orders of magnitude.44-47 In water, LFD-01 is only weakly absorbing with a main absorption peak at 417 nm. CB[7] enhanced the solubility of LFD-01 as monitored by UV-vis spectroscopy (see Fig. 4a) with a bathochromic shift of ≈ 46 nm following the trend observed in organic solvents that supports disaggregation of LFD-01 upon binding.48,49 This disaggregation phenomenon is confirmed by the strong increase of the fluorescence quantum yield of Φf = 0.597 (Φf alone in water = 0.021, see Table S2) and the red-shift of the emission peak (λem = 580 nm compared to 572 nm for LFD-01 alone, see Fig. 4b) that supports emission enhancement induced by disassembly (DIEE). This concept is based first on the self-assembly of fluorescent compounds for which sufficient spatial proximity induces fluorescence quenching


Page 5 of 12

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


resulting in dormant or latent fluorescence particles (LFPs).24-28 However, the supramolecular nature of these systems render them amenable to disassembly when placed with molecular binders stronger than themselves and resulting in disaggregation induced fluorescence recovery. We also noted the absence of precipitation with time when CB[7] was present. Job’s plots based on UV-vis spectroscopy are in line with a 1:1 stoichiometry (see Figure S21). UV-vis titrations are in good agreement with a monomeric type of binding and a binding constant Ka = 2.2±0.3 × 104 M-1 was determined by non-linear curve fit (see Fig. 4a, inset). This value is similar to the value of Ka = 4.0±0.7 × 104 M-1 determined for the more water soluble N-CH3 analogue toward CB[7] (LFD-02, see Figure S23). High resolution ESI mass spectrometry of a mixture of LFD-01 (0.1 mM) and CB[7] (1 mM) showed the presence of a cation of formulae C70H75N30O14+ diagnostic of a LFD01@CB[7] complex corresponding to an exact mass of 1559.6078 Da with an error below 1 ppm (see Figure S25 and Table S3). Due to the low water solubility, 1H NMR titrations were performed in DMSO-d6 and support LFD01 complexation by CB[7] through the pyridiniumhemicyanine polar head (see Fig. 5). No detectable complexation induced chemical shift changes were observed for the methylene protons of the octyl chain (see Figure S26) and for the carbazole protons. 1H NMR spectra of LFD-01 in D2O (0.3 mM) showed no peaks at room temperature as a result of aggregation. However at 80°C, the solubility raised enough to allow a 1H NMR titration to be performed. With the addition of CB[7], resonances assigned to aromatic protons split with the signals of three protons moving downfield by 0.40, 0.29 and 0.24 ppm (see Figure S27). Conversely, the signals of two sets of two protons moved upfield by 0.90 and 1.02 ppm in agreement with the behavior of the signals of protons a and b for LFD-01 titrated with CB[7] in DMSO-d6 (see Fig. 5). DFT calculations indicate that the pyridinium side is more favored (see Fig. 5c) than the octyl chain regarding CB[7] binding (see Supporting Information). Proton “e” is likely positioned near the carbonyl oxygen rim of CB[7] (slight deshielding effect), in line with the proposed DFT structure. Finally, 1H NMR of the analogous compound lacking 7 carbon atoms on the alkyl chain (N-CH3: LFD-02) showed features characteristic of pyridinium inclusion in D2O and DMSO-d6 and similar UV-vis and fluorescence properties toward CB[7] binding (see Supporting Information). Even though challenged by the low solubility of both host and guest, similar results were obtained for LFD-01 with CB[6] (1:1 binding, Figures S20) except that the fluorescence is blue-shifted with Φf ≈ 0.734 (intense green emission, Figure S31). Because CB[8] red-shifted the emission maximum to 588 nm (1:2 binding and Φf ≈ 0.338, Figures S22 and S32), LFD-01 behaves as a selective marker for the presence of CB[n] (n = 6, 7, or 8).

Figure 5. Binding mode of LFD-01 in CB[7]. (a) Excerpt of 1 the aromatic region for the H-NMR titration of LFD-01 (1 mM) with CB[7] in DMSO-d6 (• : unassigned signals) and (b) assignment of the corresponding protons chemical shifts. (c) Lowest energy DFT minimized structure (B3LYP/6-31G(d)) of the 1:1 inclusion complex of LFD-01 with CB[7] (guest aliphatic chain and CB[7] hydrogen atoms removed for clarity). Note the position of proton “e”, close to the CB[7] portal.

The emission spectrum spans over an ≈ 40 nm window (from green to orange) depending on the CB considered with very large Stokes shifts of > 100 nm in line with previous reports.44,47 For a different carbazole derivative, Nau et al. have shown that CB[6] dramatically changed the fluorescence properties of the dye50 due to CB[6]-assisted dye protonation (supramolecular pKa shift), enabling to monitor the enzymatic activity of lysine decarboxylase. In this work, the carbazole LFD-01 dye contains no protonable amine sites close to neutral pH51 that could explain such fluorescence increase. Instead, CB[7] likely bound LFD-01 by the pyridinium head32 in a manner isolating the fluorophores from one another and eventually restoring the latent fluorescence. Alternatively, complexation on the surface of LFN-01 nanoparticles by CB[7] (Complexation Induced Emission Enhancement, CIEE) cannot be completely ruled out but DLS studies are in line with a



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

dramatic decrease in particle size (to ≈ 2 nm) that matches well the expected size for a 1:1 LFD-01@CB[7] complex (see Figure S33). Finally, TEM of samples of LFD-01 or LFD-02 containing CB[7] show almost no remaining nanoparticles (see Figure S34). Also, amantadine replaced the dye in the CB[7] cavity resulting in fluorescence decrease that we assign to re-aggregation of LFD-01 owing to its very hydrophobic nature. However, the process is incomplete with about 50% of the fluorescence lost (Figure S35) suggesting that approximately half of LFD-01 reformed particles. Thus, DLS, UV, fluorescence, ESI-MS, TEM and NMR spectroscopy in DMSO and in water, all support inclusion complexation and a CB[7] triggered DIEE phenomenon. Similar results obtained for LFD-02 also support 1:1 complexation (see Supporting Information) and DIEE. Even though the CB cavity effect (low polarizability and solvent exclusion effects among others) is difficult to disentangle from the expected intrinsic fluorescence recovery upon disassembly, the high fluorescence increases observed showed good potential for the sensing of other macrocycles. α-CD, β-CD, γ-CD, DM-βCD, SBE-β-CD, TM-β-CD and a water soluble resorcinarene capsule52 also triggered sizable emission enhancement (Figure S36) showing good promise as a fluorescent tracker for new macrocycles. Because we also have interest in peptide materials, we decided to assess the usefulness of the LFPs to quickly evidence dipeptide aggregation (instant fluorescence turn-on) and possibly use them as staining agents for confocal fluorescence microscopy. Sensing of dipeptide aggregation. Increasing efforts are devoted to decipher the amino acids or the peptide sequences favoring aggregation, not only in water (peptide nanotubes, fibrillation, cancer therapy), but also in organic solvents (smart materials, catalysts, sensors, templates for inorganic materials).53,54 For example the self-assembly of a hydrophobic dipeptide has recently been shown to be closely related to inhibition of in vivo cancer progression.55 The impact of the presence and position of hydrophobic residues on the self-assembling propensity of di-56 and tripeptides57 has been investigated. The aggregation ability of several peptides that were synthesized could be predicted and DLS, DOSY-NMR and TEM revealed aggregation. However, peptides and proteins self-assembling at the nanoscale require time-consuming, tedious characterizations,58 and a rapid method to quickly assess aggregation would be convenient. Recently, we showed that the Fmoc-Leu-Leu-OBn dipeptide triggered solvents gelation by ultrasound59,60 and showed supramolecular gelation of Fmoc-Leu-Leu in the presence of quantum dots in toluene.61 We then realized that Fmoc-Leu-Leu dissolved in water at basic pH also produced self-assembled structures and we looked at the LFD-01 fluorescence to clarify this phenomenon. As the 0.1-36 mM dipeptide concentration window was chosen throughout the study, a fixed NaOH concentration of 36 mM was used to ensure full dissolution of Fmoc-Leu-Leu which is otherwise hardly watersoluble.

Page 6 of 12

Figure 6. Confocal fluorescence microscopy of dipeptide aggregates. Confocal images of (a, b) Leu-Leu, (c) Fmoc-LeuLeu (see text) and (d) Phe-Phe with LFD-01 (100 µM, λexc = 488 nm).

At 36 mM of Fmoc-dipeptide (acid form), the pH was close to 8 (equimolar amount of acid and base) and prevented Fmoc deprotection. However, for all concentrations below 36 mM (1, 4 and 12 mM), the excess of base triggered deprotection producing the dipeptide Leu-Leu that rapidly self-assembled right after its formation (NMR monitoring, see Figure S37 and text below). This technique has double advantages of (i) avoiding the use of an organic solvent for peptide dissolution that could dissolve LFD-01 resulting in undesired fluorescence enhancements and (ii) allow studying two kinds of hydrophobic peptides (protected and unprotected) affording different types of aggregates. When a 100 µM suspension of LFP-01 was mixed with Fmoc-Leu-Leu in water at basic pH, a yellow fluorescence appeared and gradually increased with time by about 1-2 orders of magnitude for 3-4 minutes before slowly decreasing. At 1 and 4 mM (Leu-Leu) concentration, confocal fluorescence microscopy enabled to clearly identify vesicles of approximate dimensions ≈ 500 nm-5 µm (see Fig. 6a). Due to the sensitivity of the microscope, the quenched LFP-01 particles could be identified (Figure S38a) but are no longer present in the peptide samples suggesting disassembly of LFP-01 toward LFD-01, expected to be inserted in the dipeptide aggregates. DLS measurements without dye allowed monitoring the process of vesicles formation and characterizing particles of sizes 200-400 nm in a 20-70 minutes’ time frame while higher size particles of dimensions ~ 500 nm-1.5 µm appear after that time (see Figure S39).


Page 7 of 12

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


At 8 mM, Leu-Leu was reported to form vesicles in water62 and we surmised that LFP-01 disassemble as the newly formed Leu-Leu vesicles offer a better hydrophobic medium for LFD-01 sequestration. Interestingly, a brighter fluorescence can be seen at the periphery of the vesicles suggesting that LFD-01 preferentially complex on their surfaces as expected for a vesicular system. Environmental-SEM (humidity control) at 4 mM dipeptide and without dye initially showed spheres of dimensions ≈0.5-5 µm and the appearance of tubes or fibers upon drying (see Figure S40). At 12 mM (Leu-Leu), small spheres are present after 100 minutes incubation and they are gradually replaced by straight bidentate structures that have grown with time eventually reaching dimensions of ≈ 100±20 µm × 10±5 µm (major phase, see Fig. 6b) and thinner fibers that seem having evolved from isolated nucleation sites (see Fig. 6b arrows).63 Upon drying, the straight structures and the fibers are frozen and a film and bright spheres appeared (see Figure S38). At 36 mM (Fmoc-Leu-Leu), a weak supramolecular gel slowly formed with thinner fibers (see Fig. 6c).61,64,65 2D-NOESY spectra showed strong cross-correlations between the signals of the aromatic moieties and those of the leucine side chains (isobutyl) reflecting intermolecular interactions between these groups, right from the beginning of the experiment (see Figure S41).61 However, gradually raising the temperature to 80°C afforded the 1H NMR spectrum of isolated Fmoc-Leu-Leu (sharp signals in the 7.2-7.8 ppm region) illustrating the dynamic nature of the hydrogel (see Figure S42). Also, the dipeptide Phe-Phe has started to be widely investigated owing to its peculiar properties66 of forming tubes and fibers. A mixture of Phe-Phe and LFD-01 was submitted to ultrasound for 2 minutes in water before imaging. Surprisingly, Phe-Phe microcrystals were clearly seen thanks to LFD-01 that presumably covered the hydrophobic surface of the insoluble microcrystals (see Fig. 6d, confirmed by PXRD, Figure S43 and SEM after gold coating, see Figure S44). Fluorescence monitoring of LFD-01 at basic pH in the presence of Fmoc-Leu-Leu at 4 mM (Leu-Leu vesicles), 12 mM (Leu-Leu vesicles, fibers) and 36 mM (Fmoc-Leu-Leu fibers) showed a bright emission, right from the beginning of the self-assembling process (see Figure S45) and after stabilization (after 1 hour, see Fig. 7a). This shows that LFD-01 can in principle rapidly and easily detect the early stages of self-assembling peptides in water. Interestingly, exciting Fmoc-Leu-Leu (36 mM) samples containing LFD-01 (1 mM) at 262 nm, where the only fluorescence of the fluorenyl moiety is expected to be observed at 310 nm, have shown another peak at 555 nm that gradually blue-shifted to 530 nm with time (see Fig. 7b).

Figure 7. Fluorescence sensing of dipeptide aggregation. (a) Fluorescence spectra of LFD-01 (100 µM) at basic pH with Fmoc-Leu-Leu at 4 mM (Leu-leu), 12 mM (Leu-Leu) and 36 mM (Fmoc-Leu-Leu, λexc = 420 nm, incubation time = 1 hour, grey trace, bottom = spectrum of LFD-01 alone at 100 µM). (b) Evolution of fluorescence spectra of Fmoc-Leu-Leu (36 mM) and LFD-01 (1 mM) with time over 114 min (λexc = 262 nm, last spectrum, bold yellow recorded after 16 hours).

Since there is a small but significant spectral overlap between the emission spectrum of Fmoc-Leu-Leu and the absorption spectrum of LFD-01, this could be a cascade energy transfer from the excited fluorenyl moieties of Fmoc-Leu-Leu to LFD-01 emission67 due to their spatial proximity within the fibers of the network. Nevertheless, even if FRET experiments suggest LFP-01 dis-aggregation and no initial LFP-01 particles (Figure S38a) were observed in confocal images (Figure 6), fluorescence recovery by the particles binding on the surface of the aggregated structures cannot be completely ruled out. Control experiments with the tripeptide Gly-Gly-Gly reported as not or limited self-assembling57 showed almost no fluorescence increase upon addition of LFP-01. We believe that LFD-01 must have a limited influence in the peptide self-assemblies due to the low ratio of dye used with respect to peptide concentrations. Further evidence come from DLS and environmental SEM showing vesicles and fibers very similar to those observed by confocal microscopy. Hence, it has been possible to monitor the aggrega-



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

tion of dipeptides and identify the formation of vesicles, straight structures and fibers by the fluorescence and dynamic properties of LFP-01 particles. Sensing of polysaccharide aggregation. Beside peptide aggregation, sizable fluorescence enhancements were noted for LFP-01 in the presence of alginate. This natural ionic polysaccharide is made of 1,4-linked guluronate and mannuronate monomers. LFD-01 shows a bright emission at 542 nm with alginate and Ca2+ ions (see Fig. 8) as previously observed with CB[n] or dipeptides.

Page 8 of 12

accepted second supramolecular event affording hydrogels. Indeed, Ca2+ ions are believed to cross-link alginate chains and strengthen fibers networks. Confocal microscopy showed a fluorescent matrix (see Fig. 8d) together with the previously observed alginate spheres. In this context, helix wrapping of the polysaccharide around LFD-01 molecules is a possible mechanism for the DIEE observed as previously reported for the binding of a dipolar azo dye with schizophyllan.69 The detection limit regarding LFD-01 concentration with respect to alginate sensing is about 1 µM of LFD-01 and 50 µM LFP-01 particles are able to sense alginate aggregation (water gelation) at a concentration of 0.1% weight, but not below (with 5% CaCl2), so 1 mg alginate in 1 mL of aqueous solution (Figure S46). However, alginate solutions are complex media comprising water clusters, ionic distributions and microstructures at different degrees of cross-linking where inhomogeneity can play significant roles.70 Fluorescence measurements using amylose, showed interesting intensity enhancements suggesting binding of LFD-01 in the helix-shaped hydrophobic tunnels of amylose mimicking the cavities of cyclodextrins (Figure S47). Gellan, kappa-carrageenan, and a lipopolysaccharide have also been tested by LFP-01 resulting in less intense fluorescence responses but with interesting emission shifts (Figure S48). Further studies will be necessary to elucidate this phenomenon but these experiments already point to a relatively selective PL response from the LFP-01 particles to alginate in terms of PL intensity and peak position.

CONCLUSIONS Figure 8. Fluorescence sensing of polysaccharide aggregation. (a) Fluorescence increase of LFD-01 (50 µM) with alginate (1% wgt) in the absence of calcium ions. (b) as in (a) but after injection of the alginate solution in a CaCl2 solution (5% wgt, gel phase). (c) Confocal microscopy image of the algi2+ nate solution (1% wgt) with LFP-01 (100 µM) without Ca 2+ ions and (d) in the presence of Ca ions (5% wgt).

For alginate gels, the “egg-box” model is largely accepted as a calcium triggered gelation mechanism that essentially proceeds in a two-step manner involving a strong dimerization of the polysaccharide chains followed by inter dimer associations.68 The fluorescence is less important when calcium ions are not present (see Fig. 8a). Again, the quenched LFP-01 particles (Figure S38a) are not detected in the polysaccharide samples, in line with disassembly of LFP-01 and insertion of LFD-01 in the polysaccharide accompanied by fluorescence turn-on. LFD-01 was found to be localized in sodium alginate aggregates in the form of large spheres of dimensions ≈ 10-100 µm as observed by confocal microscopy (see Fig. 8c). However, with Ca2+ ions, the fluorescence is more pronounced (see Fig. 8b) and assigned to the signature of the generally

The reported stylbazolium Latent Fluorescence Particles (LFPs) have a dormant fluorescence property but the addition of relevant supramolecular structures results in the disassembly of the particles by equilibria displacements and sequestration of the dye that becomes strongly emissive in the newly available nanospaces. Cucurbit[n]urils have been successfully used as binders (NMR, MS, UV and fluorescence spectroscopies, DLS and TEM) to check the dynamic nature of the LFPs and trigger Disassembly Induced Emission Enhancement (DIEE). The resulting emission wavelength is different for CB[n] (n = 6, 7, 8), and we now routinely use LFP-01 to quickly assess the nature of the CBs obtained after purification (emitted light under a cheap UV lamp at 365 nm: green emission: CB[6], yellow emission: CB[7] and orange emission: CB[8]) before NMR and MS characterizations. The LFPs can also probe the aggregation propensity of several families of self-assembling structures with an easily readable output signal (intense emission at 365 nm under a UV lamp for some aggregating peptides and polysaccharides). LFD-01 could trace the formation of vesicles, fibers, microcrystals, spheres and gel networks, showing an interesting polymorphism of the supramolecular assemblies of the Leu-Leu dipeptides (NOE and VT-NMR, DLS, SEM, PL spectroscopy, FRET experiments and confocal fluores-


Page 9 of 12

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


cence microscopy) pointing to highly dynamic objects whose outcome depends on several parameters. LFP-01 particles were also able to monitor the stepwise, calcium triggered hydrogel formation by the polysaccharide alginate as assessed by PL spectroscopy and confocal fluorescence microscopy. In principle, LFP-01 could also be used for the rapid screening of alginate binders by fluorescence displacement assays, or to easily investigate the aggregation propensity of other polysaccharides. The hydrophobic/hydrophilic balance and the cationic nature of LFD-01 are probably at the origin of its peculiar self-assembling yet dynamic nature, amenable for fluorescence probing of a variety of supramolecular structures. Given the large fluorescence enhancements with other families of macrocycles, carbazole dye LFD-01 could be used as a fluorescent tracker for the rapid identification of new macrocycles. A screening approach is currently being studied in our laboratories.

LFP, latent fluorescence particle; LFD, latent fluorescence dye ; LFN; latent fluorescence nanoparticle; CB[n], cucurbit[n]uril; CD, cyclodextrin; DIEE, disaggregation induced emission enhancement; CIEE, complexation induced emission enhancement; DLS, dynamic light scattering; SEM, scanning electron microscopy; TEM, transmission electron microscopy; α-CD, α-cyclodextrin; β-CD, β-cyclodextrin; DM-β-CD, 2,6-di-O-methyl-β-cyclodextrin; SBE-β-CD, sulfobutyl ether-β-cyclodextrin; TM-β-CD, 2,3,6-tri-O-methyl-βcyclodextrin; DOSY, diffusion ordered spectroscopy; NOESY, nuclear overhauser effect spectroscopy; Leu-Leu, leucylleucine; Phe-Phe, phenylalanyl-phenylalanine; Gly-gly-gly, glycyl-glycyl-glycine; PXRD, powder X-ray diffraction.

REFERENCES 1.

2.

EXPERIMENTAL SECTION Procedure for the synthesis of LFD-01 and LFD-02. For the details of the preparation and characterization of LFD-01 and LFD-02, see Supporting Information. Briefly, 4-picoline has been alkylated with methyl iodide followed by a Knoevenagel condensation of the picolinium salt with 9-octyl-9H-carbazole-3-carbaldehyde affording a unique E-isomer for a two steps overall yield of 92%.

3.

4.

5.

6.

ASSOCIATED CONTENT Supporting Information. Methods and characterizations. Additional NMR spectroscopy, mass spectrometry, ele-

mental analysis, UV-visible spectroscopy, fluorescence spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), confocal fluorescence microscopy and DFT calculations. “This material is available free of charge

7.

8.

via the Internet at http://pubs.acs.org.” 9.

AUTHOR INFORMATION Corresponding Authors * E-mail: [email protected] (R. W.). * E-mail: [email protected] (D. B.). * E-mail: [email protected] (O. O.).

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT

11.

12.

CNRS, Aix-Marseille Université, and Région PACA (project “Masked Spins”) are acknowledged for financial supports. Nicolas Vidal, Pierre Stocker and Mathieu Cassien are acknowledged for their help with the fluorescence instrument. Virginie Hornebecq is gratefully acknowledged for the PXRD analysis. We also thank Laszlo Jicsinszky (Cyclolab) for a generous gift of γ-cyclodextrin.

ABBREVIATIONS

10.

13.

14. 15.

Chartrand, T. L.; Bargh, J. A. The Chameleon Effect: The Perception–Behavior Link and Social Interaction. J. Pers. Soc. Psychol. 1999, 76, 893−910. Nelson, A. E.; Walsh, J. Chameleon Vector Bosons. Phys. Rev. D 2008, 77, 095006. Teyssier, J.; Saenko, S. V.; van der Marel, D.; Milinkovitch, M. C. Photonic Crystals Cause Active Colour Change in Chameleons. Nat. Commun. 2015, 6, 6368. Li, L.; Wang, C.; Wu, J.; Tse, Y. C.; Cai, Y.-P.; Wong, K. M.-C. A Molecular Chameleon with Fluorescein and Rhodamine Spectroscopic Behaviors. Inorg. Chem. 2016, 55, 205−213. Wetzl, B. K.; Yarmoluk, S. M.; Craig, D. B.; Wolfbeis, O. S. Chameleon Labels for Staining and Quantifying Proteins. Angew. Chem., Int. Ed. 2004, 43, 5400–5402. Gorris, H.; Saleh, S. M.; Groegel, D. B. M.; Ernst, S.; Reiner, K.; Mustroph, H.; Wolfbeis, O. S. Long-Wavelength Absorbing and Fluorescent Chameleon Labels for Proteins, Peptides, and Amines. Bioconjugate Chem. 2011, 22, 1433–1437. Kostenko, O. M.; Kovalska, V. B.; Volkova, K. D.; Shaytanov, P.; Kocheshev, I. O.; Slominskiy, Y. L.; Pisareva, I. V.; Yarmoluk, S. M. New Method for Covalent Fluorescent Biomolecule Labeling with Hemicyanine Dye. J. Fluoresc. 2006, 16, 589–593. Dahne, L.; Horvath, A.; Weiser, G.; Reck, G. The Chameleon Dye 1,7-Bis(dimethylamino)heptamethine. Adv. Mater. 1996, 8, 486– 490. Chen, H.; Lin, W.; Jiang, W.; Dong, B.; Cui, H.; Tang, Y. LockedFlavylium Fluorescent Dyes with Tunable Emission Wavelengths based on Intramolecular Charge Transfer for Multi-Color Ratiometric Fluorescence Imaging. Chem. Commun. 2015, 51, 6968−6971. Yang, Y.; Lowry, M.; Schowalter, C. M.; Fakayode, S. O.; Escobedo, J. O.; Xu, X.; Zhang, H.; Jensen, T. J.; Fronczek, F. R.; Warner, I. M.; Strongin, R. M. An Organic White Light-Emitting Fluorophore. J. Am. Chem. Soc. 2006, 128, 14081−14092. Felip-Leon, C.; Diaz-Oltra, S.; Galindo, F.; Miravet, J. F. Chameleonic, Light Harvesting Photonic Gels Based on Orthogonal Molecular Fibrillization. Chem. Mater. 2016, 28, 7964−7972. Hu, W.; Lu, N.; Zhang, H.; Wang, Y.; Kehagias, N.; Reboud, V.; Torres, C. M. S.; Hao, J.; Li, W.; Fuchs, H.; Chi, L. Multicolor Emission on Prepatterned Substrates Using a Single Dye Species. Adv. Mater. 2007, 19, 2119–2123. Yamaguchi, E.; Wang, C.; Fukazawa, A.; Taki, M.; Sato, Y.; Sasaki, T.; Ueda, M.; Sasaki, N.; Higashiyama, T.; Yamaguchi, S. Environment-Sensitive Fluorescent Probe: a Benzophosphole Oxide with an Electron-Donating Substituent. Angew. Chem. Int. Ed. 2015, 54, 4539–4543. Buncel, E.; Rajagopal, S. Solvatochromism and Solvent Polarity Scales. Acc. Chem. Res. 1990, 23, 226–231. Vazquez, M. E.; Blanco, J. B.; Imperiali, B. Photophysics and



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

16.

17.

18.

19.

20.

21.

22. 23.

24.

25.

26.

27.

28.

29.

30.

31. 32.

33.

Biological Applications of the Environment-Sensitive Fluorophore 6-N,N-Dimethylamino-2,3-naphthalimide. J. Am. Chem. Soc. 2005, 127, 1300−1306. Hawe, A.; Sutter, M.; Jiskoot, W. Extrinsic Fluorescent Dyes as Tools for Protein Characterization. Pharm. Res. 2008, 25, 1487– 1499. Lagona, J.; Mukhopadhyay, P.; Chakrabarti, S.; Isaacs, L. The Cucurbit[n]uril Family. Angew. Chem., Int. Ed. 2005, 44, 4844−4870. Lee, J. W.; Samal, S.; Selvapalam, N.; Kim, H.-J.; Kim, K. Cucurbituril Homologues and Derivatives: New Opportunities in Supramolecular Chemistry. Acc. Chem. Res. 2003, 36, 621−630. Barrow, S. J.; Kasera, S.; Rowland, M. J.; del Barrio, J.; Scherman, O. A. Cucurbituril-Based Molecular Recognition. Chem. Rev. 2015, 115, 12320−12406. Dziuba, D.; Jurkiewicz, P.; Cebecauer, M.; Hof, M.; Hocek, M. A Rotational BODIPY Nucleotide: An Environment-Sensitive Fluorescence-Lifetime Probe for DNA Interactions and Applications in Live-Cell Microscopy. Angew. Chem. Int. Ed. 2016, 55, 174−178. Yan, P.; Acker, C. D.; Zhou, W.-L.; Lee, P.; Bollensdorff, C.; Negrean, A.; Lotti, J.; Sacconi, L.; Antic, S. D.; Kohl, P.; Mansvelder, H. D.; Pavone, F. S.; Loew, L. M. Palette of Fluorinated Voltage-Sensitive Hemicyanine Dyes. Proc. Natl. Acad. Sci. USA 2012, 109, 20443–20448. Loew, L. M. Potentiometric Dyes: Imaging Electrical Activity of Cell Membranes. Pure & Appl. Chem. 1996, 68, 1405–1409. Higgins, D. A.; Collinson, M. M.; Saroja, G.; Bardo, A. M. SingleMolecule Spectroscopic Studies of Nanoscale Heterogeneity in Organically Modified Silicate Thin Films. Chem. Mater. 2002, 14, 3734–3744. Mizusawa, K.; Takaoka, Y.; Hamachi, I. Specific Cell Surface Protein Imaging by Extended Self-Assembling Fluorescent Turn-on Nanoprobes. J. Am. Chem. Soc. 2012, 134, 13386−13395. Mizusawa, K.; Ishida, Y.; Takaoka, Y.; Miyagawa, M.; Tsukiji, S.; Hamachi, I. Disassembly-Driven Turn-On Fluorescent Nanoprobes for Selective Protein Detection. J. Am. Chem. Soc. 2010, 132, 7291−7293. He, Q.; Fan, X.; Sun, S.; Li, H.; Pei, Y.; Xu, Y. Highly Selective Turn-On Detection of (Strept)Avidin based on Self-Assembled Near-Infrared Fluorescent Probes. RSC Adv. 2015, 5, 38571–38576. Wang, K.-R.; An, H.-W.; Rong, R.-X.; Cao, Z.-R.; Li, X.-L. Fluorescence Turn-On Sensing of Protein based on Mannose Functionalized Perylene Bisimides and its Fluorescence Imaging. Biosens. Bioeletron. 2014, 58, 27−32. Anees, P.; Sreejith, S.; Ajayaghosh, A. Self-Assembled NearInfrared Dye Nanoparticles as a Selective Protein Sensor by Activation of a Dormant Fluorophore. J. Am. Chem. Soc. 2014, 136, 13233−13239. An, B.-K.; Gierschner, J.; Park, S. Y. π-Conjugated Cyanostilbene Derivatives: A Unique Self-Assembly Motif for Molecular Nanostructures with Enhanced Emission and Transport. Acc. Chem. Res. 2012, 45, 544–554. Würthner, F.; Saha-Möller, C. R.; Fimmel, B.; Ogi, S.; Leowanawat, P.; Schmidt, D. Perylene Bisimide Dye Assemblies as Archetype Functional Supramolecular Materials. Chem. Rev. 2016, 116, 962–1052. Wang, L.; Xu, L.; Kuang, H.; Xu, C.; Kotov, N. A. Dynamic Nanoparticle Assemblies. Acc. Chem. Res. 2012, 45, 1916–1926. Li, S.; Chen, H.; Yang, X.; Bardelang, D.; Wyman, I. W.; Wan, J.; Lee, S. M. Y.; Wang, R. Supramolecular Inhibition of Neurodegeneration by a Synthetic Receptor. ACS Med. Chem. Lett. 2015, 6, 1174−1178. Florea, M.; Nau, W. M. Strong Binding of Hydrocarbons to Cucurbituril Probed by Fluorescent Dye Displacement: a Supramolecular Gas-Sensing Ensemble. Angew. Chem. Int. Ed. 2011, 50, 9338–9342.

34.

35.

36.

37.

38.

39.

40.

41.

42. 43.

44.

45.

46.

47.

48.

49.

50.

51.

52.

Page 10 of 12

Cao, L.; Sekutor, M.; Zavalij, P. Y.; Mlinaric-Majerski, K.; Glaser, R.; Isaacs, L. Cucurbit[7]uril⋅Guest Pair with an Attomolar Dissociation Constant. Angew. Chem., Int. Ed. 2014, 53, 988–993. Shetty, D.; Khedkar, J. K.; Park, K. M.; Kim, K. Can We Beat the Biotin–Avidin Pair?: Cucurbit[7]uril-Based Ultrahigh Affinity Host–Guest Complexes and their Applications. Chem. Soc. Rev. 2015, 44, 8747–8761. Wheate, N. J.; Day, A. I.; Blanch, R. J.; Arnold, A. P.; Cullinane, C.; Collins, J. G. Multi-Nuclear Platinum Complexes Encapsulated in Cucurbit[n]uril as an Approach to Reduce Toxicity in Cancer Treatment. Chem. Commun. 2004, 1424−1425. Jeon, Y. J.; Kim, S.-Y.; Ko, Y. H.; Sakamoto, S.; Yamaguchi, K.; Kim, K. Novel Molecular Drug Carrier: Encapsulation of Oxaliplatin in Cucurbit[7]uril and its Effects on Stability and Reactivity of the Drug. Org. Biomol. Chem. 2005, 3, 2122−2125. Yang, X.; Wang, Z.; Niu, Y.; Chen, X.; Lee, S. M. Y.; Wang, R. Influence of Supramolecular Encapsulation of Camptothecin by Cucurbit[7]uril: Reduced Toxicity and Preserved Anti-Cancer Activity. Med. Chem. Commun. 2016, 7, 1392−1397. Wang, W.; Kaifer, A. E. Electrochemical Switching and Size Selection in Cucurbit[8]uril-Mediated Dendrimer Self-Assembly. Angew. Chem., Int. Ed. 2006, 45, 7042−7046. Reczek, J. J.; Kennedy, A. A.; Halbert, B. T.; Urbach, A. R. Multivalent Recognition of Peptides by Modular Self-Assembled Receptors. J. Am. Chem. Soc. 2009, 131, 2408−2415. Rauwald, U.; Scherman, O. A. Supramolecular Block Copolymers with Cucurbit[8]uril in Water. Angew. Chem., Int. Ed. 2008, 47, 3950−3953. Marquez, C.; Nau, W. M. Polarizabilities Inside Molecular Containers. Angew. Chem., Int. Ed. 2001, 40, 4387–4390. Dsouza, R. N.; Pischel, U.; Nau, W. M. Fluorescent Dyes and Their Supramolecular Host/Guest Complexes with Macrocycles in Aqueous Solution. Chem. Rev. 2011, 111, 7941–7980. Bhasikuttan, A. C.; Mohanty, J.; Nau, W. M.; Pal, H. Efficient Fluorescence Enhancement and Cooperative Binding of an Organic Dye in a Supra-biomolecular Host–Protein Assembly. Angew. Chem., Int. Ed. 2007, 46, 4120–4122. Megyesi, M.; Biczok, L.; Jablonkai, I. Highly Sensitive Fluorescence Response to Inclusion Complex Formation of Berberine Alkaloid with Cucurbit[7]uril. J. Phys. Chem. C 2008, 112, 3410–3416. Biedermann, F.; Elmalem, E.; Ghosh, I.; Nau, W. M.; Scherman, O. A. Strongly Fluorescent, Switchable Perylene Bis(diimide) Host– Guest Complexes with Cucurbit[8]uril in Water. Angew. Chem., Int. Ed. 2012, 51, 7739−7743. Freitag, M.; Gundlach, L.; Piotrowiak, P.; Galoppini, E. Fluorescence Enhancement of Di-p-tolyl Viologen by Complexation in Cucurbit[7]uril. J. Am. Chem. Soc. 2012, 134, 3358−3366. Xing, P.; Chen, H.; Ma, M.; Xu, X.; Hao, A.; Zhao, Y. Light and Cucurbit[7]uril Complexation Dual-Responsiveness of a Cyanostilbene-Based Self-Assembled System. Nanoscale 2016, 8, 1892–1896. Pais, V. F.; Carvalho, E. F. A.; Tomé, J. P. C.; Pischel, U. Supramolecular Control of Phthalocyanine Dye Aggregation. Supramol. Chem. 2014, 26, 642–647. Praetorius, A.; Bailey, D. M.; Schwarzlose, T.; Nau, W. M. Design of a Fluorescent Dye for Indicator Displacement from Cucurbiturils: A Macrocycle-Responsive Fluorescent Switch Operating through a pKa Shift. Org. Lett. 2008, 10, 4089–4092. Chen, H. J.; Hakka, L. E.; Hinman, R. L.; Kresge, A. J.; Whipple, E. B. Basic Strength of Carbazole. Estimate of the Nitrogen Basicity of Pyrrole and Indole. J. Am. Chem. Soc. 1971, 93, 5102−5107. Ayhan, M. M.; Casano, G.; Karoui, H.; Rockenbauer, A.; Monnier, V.; Hardy, M.; Tordo, P.; Bardelang, D.; Ouari, O. EPR Studies of the Binding Properties, Guest Dynamics, and Inner-Space


Page 11 of 12

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

53.

54.

55.

56.

57.

58.

59.

60.

61.

62.

63.

64.

65.

66.

67.

68.

69.


Dimensions of a Water-Soluble Resorcinarene Capsule. Chem.−Eur. J. 2015, 21, 16404−16410. Cavalli, S.; Albericio, F.; Kros, A. Amphiphilic Peptides and their Cross-Disciplinary Role as Building Blocks for Nanoscience. Chem. Soc. Rev. 2010, 39, 241−263. Fleming, S.; Ulijn, R. V. Design of Nanostructures based on Aromatic Peptide Amphiphiles. Chem. Soc. Rev. 2014, 43, 8150– 8177. Kuang, Y.; Du, X.; Zhou, J.; Xu, B. Supramolecular Nanofibrils Inhibit Cancer Progression In Vitro and In Vivo. Adv. Healthcare Mater. 2014, 3, 1217–1221. Frederix, P. W. J. M.; Ulijn, R. V.; Hunt, N. T.; Tuttle, T. Virtual Screening for Dipeptide Aggregation: Toward Predictive Tools for Peptide Self-Assembly. J. Phys. Chem. Lett. 2011, 2, 2380–2384. Frederix, P. W. J. M.; Scott, G. G.; Abul-Haija, Y. M.; Kalafatovic, D.; Pappas, C. G.; Javid, N.; Hunt, N. T.; Ulijn, R. V.; Tuttle, T. Exploring the Sequence Space for (Tri-)Peptide Self-Assembly to Design and Discover New Hydrogels. Nature Chem. 2015, 7, 30– 37. Tatkiewicz, W.; Elizondo, E.; Moreno, E.; Diez-Gil, C.; Ventosa, N.; Veciana, J.; Ratera, I. Methods for Characterization of Protein Aggregates. In: Methods in Molecular Biology. Springer New York 2015, 387–401. Bardelang, D.; Camerel, F.; Margeson, J. C.; Leek, D. M.; Schmutz, M.; Zaman, Md. B.; Yu, K.; Soldatov, D. V.; Ziessel, R.; Ratcliffe, C. I.; Ripmeester, J. A. Unusual Sculpting of Dipeptide Particles by Ultrasound Induces Gelation. J. Am. Chem. Soc. 2008, 130, 3313−3315. Bardelang, D.; Zaman, Md. B.; Moudrakovski, I. L.; Pawsey, S.; Margeson, J. C.; Wang, D.; Wu, X.; Ripmeester, J. A.; Ratcliffe, C. I.; Yu, K. Interfacing Supramolecular Gels and Quantum Dots with Ultrasound: Smart Photoluminescent Dipeptide Gels. Adv. Mater. 2008, 20, 4517−4520. Zaman, Md. B.; Bardelang, D.; Prakesch, M.; Leek, D. M.; Naubron, J.-V.; Chan, G.; Wu, X.; Ripmeester, J. A.; Ratcliffe, C. I.; Yu, K. Size Reduction of CdSe/ZnS Quantum Dots by a Peptidic Amyloid Supergelator. ACS Appl. Mater. Interfaces 2012, 4, 1178−1181. Mishra, A.; Chauhan, V. S. Probing the Role of Aromaticity in the Design of Dipeptide based Nanostructures. Nanoscale 2011, 3, 945–949. Similar results have been reported before for the analogous dipeptide: FmocLG: Johnson, E. K.; Adams, D. J.; Cameron, P. J. Directed Self-Assembly of Dipeptides to Form Ultrathin Hydrogel Membranes. J. Am. Chem. Soc. 2010, 132, 5130–5136. Jayawarna, V.; Ali, M.; Jowitt, T. A.; Miller, A. F.; Saiani, A.; Gough, J. E.; Ulijn, R. V. Nanostructured Hydrogels for ThreeDimensional Cell Culture Through Self-Assembly of Fluorenylmethoxycarbonyl–Dipeptides. Adv. Mater. 2006, 18, 611– 614. Adams, D. J.; Butler, M. F.; Frith, W. J.; Kirkland, M.; Mullen, L.; Sanderson, P. A New Method for Maintaining Homogeneity During Liquid–Hydrogel Transitions Using Low Molecular Weight Hydrogelators. Soft Matter 2009, 5, 1856−1862. Yan, X.; Zhua, P.; Li, J. Self-Assembly and Application of Diphenylalanine-based Nanostructures. Chem. Soc. Rev. 2010, 39, 1877–1890. Nalluri, S. K. M.; Ulijn, R. V. Discovery of Energy Transfer Nanostructures Using Gelation-Driven Dynamic Combinatorial Libraries. Chem. Sci. 2013, 4, 3699–3705. Fraeye, I.; Duvetter, T.; Doungla, E.; Loey, A. V.; Hendrickx, M. Fine-Tuning the Properties of Pectin–Calcium Gels by Control of Pectin Fine Structure, Gel Composition and Environmental Conditions. Trends Food Sci. Technol. 2010, 21, 219–228. Numata, M.; Tamesue, S.; Fujisawa, T.; Haraguchi, S.; Hasegawa, T.; Bae, A.-H.; Li, C.; Sakurai, K.; Shinkai, S. β-1,3-Glucan Polysaccharide (Schizophyllan) Acting as a One-Dimensional Host

70.

for Creating Supramolecular Dye Assemblies. Org. Lett. 2006, 8, 5533−5536. Dandapat, M.; Mandal, D. Time-Dependent Fluorescence Stokes Shift and Molecular-Scale Dynamics in Alginate Solutions and Hydrogels. Chem. Phys. Lett. 2015, 627, 67–72.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 12

Table of Contents

ACS Paragon Plus Environment

11

Chameleonic Dye Adapts to Various Environments Shining on

Recommend Documents