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A single amino acid in a peptide sequence can play an important role to tune the self‐assembly and hydrogelation behaviour. Here, a C‐terminal cysteine‐containing ultrashort peptide hydrogelator forms hydrogel through non‐covalent and covalent interactions. Interestingly, the hydrogel is insoluble in water and buffer solutions at different pH values (1‐13) and is thixotropic and injectable. In recent years, removing dyes from contaminated water has become a significant concern because of the shortage of freshwater resources. Therefore, the adsorption of dyes through a reliable, straightforward, nontoxic, cheap, and environmentally friendly adsorbent has become a popular topic. Hence, the hydrogelator was exploited to remove organic dyes from wastewater, harnessing its applicability in the gel phase and solid supports (filter paper and cotton). [ABSTRACT FROM AUTHOR]

Over the last couple of decades, stimuli-responsive supramolecular gels comprising synthetic short peptides as building blocks have been explored for various biological and material applications. Though a wide range of stimuli has been tested depending on the structure of the peptides, light as a stimulus has attracted extensive attention due to its non-invasive, non-contaminant, and remotely controllable nature, precise spatial and temporal resolution, and wavelength tunability. The integration of molecular photo-switch and low-molecular-weight synthetic peptides may thus provide access to supramolecular self-assembled systems, notably supramolecular gels, which may be used to create dynamic, light-responsive "smart" materials with a variety of structures and functions. This short review summarizes the recent advancement in the area of light-sensitive peptide gelation. At first, a glimpse of commonly used molecular photo-switches is given, followed by a detailed description of their incorporation into peptide sequences to design light-responsive peptide gels and the mechanism of their action. Finally, the challenges and future perspectives for developing next-generation photo-responsive gels and materials are outlined. [ABSTRACT FROM AUTHOR]

Herein, we report the catalytic potential of short peptide based cross-β amyloid nanotubes with surface exposed histidine capable of binding hemin and showing facile cascade reactions, playing the dual roles of hydrolases and peroxidases, two of the most important classes of enzymes in extant biology. The activity of these simple systems exceeded those of modern and larger proteins like cytochrome C and hemoglobin. Further, evidence suggested that these self-assembled nanotubes foreshadow the process of intermediate channeling, a feature seen in the case of advanced enzymes. [ABSTRACT FROM AUTHOR]

In living systems, dissipative processes are driven by the endergonic hydrolysis of chemical fuels such as nucleoside triphosphates. Now, through a simple model system, a transient self‐assembled state is realized by utilizing the catalytic effect of histidine on the formation and breaking of ester bonds. First, histidine facilitates the ester bond formation, which then rapidly co‐assembles to form a self‐supporting gel. An out‐of‐equilibrium state is realized owing to the cooperative catalysis by the proximal histidines in the assembled state, driving the second pathway and resulting in disassembly to sol. Cooperative effects that use the dual role of imidazoles as nucleophile and as proton donor is utilized to achieve transient assemblies. This simple system mimics the structural journey seen in microtubule formation where the substrate GTP facilitates the non‐covalent assembly and triggers a cooperative catalytic process, leading to substrate hydrolysis and subsequent disassembly. Self‐driving: A simple fuel‐driven self‐assembled system is demonstrated that achieves an out‐of‐equilibrium state by dissipating energy from the assembled structures. This occurs by utilizing cooperative effects of the proximally located histidines, which catalyze the hydrolysis of ester bonds of the lipid‐tailed amphiphile. [ABSTRACT FROM AUTHOR]

Cover Feature: Disulphide Cross-Linked Ultrashort Peptide Hydrogelator for Water Remediation (Chem. Eur. J. 37/2023) Keywords: disulphide; dye removal; hydrogels; peptides; self-assembly EN disulphide dye removal hydrogels peptides self-assembly 1 1 1 07/05/23 20230703 NES 230703 B Unleashing the power of peptide hydrogels for environmental remediation b : This is a tale of an ultrashort peptide hydrogel (azo-KC) and its efficiency for wastewater treatment. Disulphide, dye removal, hydrogels, peptides, self-assembly. [Extracted from the article]

Abstract: A tandem sensor for Pd2+ and CN− ions based on perylenediimide‐peptide conjugate is reported. The probe showed high selectivity toward Pd2+ ion over other metal cations and the sensitivity was observed to be 0.55 ppb, significantly lower than other similar chemosensors. Binding with Pd2+ leads to aggregation of the ligand and consequently results in quenching of its emission. The quenched emission can be turned on in presence of CN− ions as the cyanides form stronger complex with Pd2+ leading to disaggregation of the aggregated system. The system was found to be extremely selective to CN− and the detection limit in this case was calculated to be as low as 0.226 ppb. The sensor is also utilized to construct a practical and simple TLC based tool to sense these two ions efficiently. [ABSTRACT FROM AUTHOR]

Abstract: To develop a new sensor for histone, a series of Naphthalenediimide (NDI) derivatieves were subjected to DNA binding studies and the NDI derivative with strongest affinity for DNA was selected. This NDI‐DNA hybrid is used for highly selective and sensitive detection of a DNA binding protein, histone which dislodges the intercalated NDI groups and thus “turn‐on” the emission. [ABSTRACT FROM AUTHOR]

A systematic study of the self-assemblyprocess of a viologen-containingsurfactant in aqueous medium is reported. Dodecyl-ethyl-viologendibromide(DDEV) is mixed in different proportions with dodecyltrimethylammoniumbromide (DTAB), and the physicochemical properties of micellizationare evaluated in order to find a suitable combination which does notinterfere with the micellar properties of DTAB but introduces thecharacteristic properties of viologen. In this process, 1% dopingof DDEV with DTAB was found to be the most appropriate, as negligiblechanges were observed in the physicochemical behavior of this systemwith respect to that of pure DTAB. The 1% DDEV-doped DTAB mixed micellarsystem showed the characteristic two-step reduction process for theviologen units at the interface as revealed by CV experiments. 1%mixing of DDEV with DTAB also allowed us to prepare stable w/o microemulsionscontaining viologen units at the interface which is otherwise unattainablewith pure viologen surfactants. The charge-transfer capability ofthe viologen unit to the electron-rich 2,6-dihydroxynaphthalene (DHN)moiety inside the macrocyclic host, cucurbit[8]uril (CB[8]) is alsoevaluated for this system, and surprisingly even at this very lowconcentration, the ternary complex of DDEV-DHN@CB[8] transformed themicellar assembly to uniform vesicles. All of these properties havebeen further extended to other tetraalkylammonium surfactants, andsimilar effects were observed. [ABSTRACT FROM AUTHOR]

A lysine based peptide amphiphile(PA) is designed and synthesizedfor efficient water immobilization. The PA with a minimum gelationconcentration (MGC) of 1% w/v in water shows prolonged stability andcan also efficiently immobilize aqueous mixtures of some other organicsolvents. The presence of a free amine induced pH dependency of thegelation as the PA could form hydrogel at a pH range of 1–8but failed to do so above that pH. Various spectroscopic and microscopicexperiments such as steady state fluorescence, NMR, IR, CD, and FESEMreveal the presence of hydrophobic interaction, hydrogen bond, andπ–π stacking interaction in the self-assembly process.The self-aggregation has been correlated with the design of the moleculeto show the involvement of supramolecular forces and the hierarchicalpathway. While the L analogue formed left-handed helical nanofibers,the other enantiomer showed opposite helicity. Interestingly the equimolarmixture of the isomers failed to form any fibrous aggregate. Althoughfibers formed at a subgel concentration, no helical nature was observedat this stage. The length and thickness of the fibers increased withincrease in the gelator concentration. The nanofibers formed by thegelator are used as a template to prepare mesoporous single wall silicananotubes (SWSNTs) in situ in plain water without the requirementof any organic solvent as well as any external hydrolyzing agent.The SWSNTs formed are open at both ends, are few micrometers in length,and have an average diameter of ∼10 nm. The BET isotherm showeda type IV hysteresis loop suggesting mesoporous nature of the nanotubes. [ABSTRACT FROM AUTHOR]

Achieving rapid clotting and clot stability are important unmet goals of clinical management of noncompressible hemorrhage. This study reports the development of a spatiotemporally controlled release system of an antihemorrhagic drug, etamsylate, in the management of internal hemorrhage. Gly-Arg-Gly-Asp-Ser (GRGDS) peptide-functionalized chitosan nanoparticles, with high affinity to bind with the GPIIa/IIIb receptor of activated platelets, were loaded with the drug etamsylate (etamsylate-loaded GRGDS peptide-functionalized chitosan nanoparticles; EGCSNP). Peptide conjugation was confirmed by LCMS, and the delivery system was characterized by DLS, SEM, XRD, and FTIR. In vitro study exhibited 90% drug release till 48 h fitting into the Weibull model. Plasma recalcification time and prothrombin time tests of GRGDS-functionalized nanoparticles proved that clot formation was 1.5 times faster than nonfunctionalized chitosan nanoparticles. The whole blood clotting time was increased by 2.5 times over clot formed under nonfunctionalized chitosan nanoparticles. Furthermore, the application of rheometric analysis revealed a 1.2 times stiffer clot over chitosan nanoparticles. In an in vivo liver laceration rabbit model, EGCSNP spatially localized at the internal injury site within 5 min of intravenous administration, and no rebleeding was recorded up to 3 h. The animals survived for 3 weeks after the injury, indicating the strong potential of the system for the management of noncompressible hemorrhage.

A single amino acid in a peptide sequence can play an important role to tune the self-assembly and hydrogelation behaviour. Here, a C-terminal cysteine-containing ultrashort peptide hydrogelator forms hydrogel through non-covalent and covalent interactions. Interestingly, the hydrogel is insoluble in water and buffer solutions at different pH values (1-13) and is thixotropic and injectable. In recent years, removing dyes from contaminated water has become a significant concern because of the shortage of freshwater resources. Therefore, the adsorption of dyes through a reliable, straightforward, nontoxic, cheap, and environmentally friendly adsorbent has become a popular topic. Hence, the hydrogelator was exploited to remove organic dyes from wastewater, harnessing its applicability in the gel phase and solid supports (filter paper and cotton)., (© 2023 Wiley-VCH GmbH.)

Cation-π and charge-transfer (CT) interactions are ubiquitous in nature and involved in several biological processes. Although the origin of both the interactions in isolated pairs has extensively been studied, CT interactions are more prominent in supramolecular chemistry. Involvement of cation-π interactions in the preparation of advanced functional soft materials is uncommon. Moreover, a combination of these two interactions within a pair of electron donor (D) and acceptor (A) is uncharted. Here, we present a rational design to incorporate a combination of these two interactions within a D-A pair. A pyrene-peptide conjugate exhibits a combination of cation-π and CT interactions with a cationic naphthalenediimide (NDI) molecule in water. Nuclear Overhauser effect spectroscopy NMR along with other techniques and density functional theory calculations reveal the involvement of these interactions. The π-planes of pyrene and NDI adopt an angle of 56° to satisfy both the interactions, whereas β-sheet formation by the peptide sequence facilitates self-assembly. Notably, the binary system forms a self-supporting hydrogel at a higher concentration. The hydrogel shows efficient self-healing and injectable property. The hydrogel retains its thixotropic nature even at an elevated temperature. Broadly, we demonstrate a pathway that should prove pertinent to various areas, ranging from understanding biological assembly to peptide-based functional soft materials.

In living systems, dissipative processes are driven by the endergonic hydrolysis of chemical fuels such as nucleoside triphosphates. Now, through a simple model system, a transient self-assembled state is realized by utilizing the catalytic effect of histidine on the formation and breaking of ester bonds. First, histidine facilitates the ester bond formation, which then rapidly co-assembles to form a self-supporting gel. An out-of-equilibrium state is realized owing to the cooperative catalysis by the proximal histidines in the assembled state, driving the second pathway and resulting in disassembly to sol. Cooperative effects that use the dual role of imidazoles as nucleophile and as proton donor is utilized to achieve transient assemblies. This simple system mimics the structural journey seen in microtubule formation where the substrate GTP facilitates the non-covalent assembly and triggers a cooperative catalytic process, leading to substrate hydrolysis and subsequent disassembly., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Molecular organization of electron-deficient aromatic systems like perylenediimides (PDI) is extremely appealing, as they are potential candidates for organic electronics. The performance of these molecules in such applications primarily depends on the self-organization of the molecules. However, any correlation between the morphology of these self-assembled semiconducting molecules and their electrical performances has not yet been formulated. Herein, for the first time, we have made an effort to find such a correlation by studying the self-assembly, morphology, and their conducting properties for a peptide-PDI conjugate. The PDI conjugate formed fiber-like morphology in relatively nonpolar solvents (THF and CHCl 3 ) while in more polar solvents (HFIP, MeOH, ACN, and acetone), spherical morphology could be found. Interestingly, the self-assembly and the morphologies showed a clear dependence on the solvent polarity. In polar solvents, the conjugate aggregates more efficiently than in the nonpolar solvents, and with decrease in solvent polarity, the dimension of the nanostructures increased. However, in all the tested solvents, irrespective of their polarity, the PDI-peptide conjugate adopts a right-handed helicity. To find a correlation between the morphologies with the conducting property, detailed electrical characterization of these nanostructures was carried out. While no significant change could be observed for the dc conductivities of these nanostructures, the ac conductivities show prominent difference at the low-frequency region. A dispersion of conductivity was observed for the nanospheres due to the polarization effect. A critical correlation between the nanostructures and the activation energy was observed as with decrease in radii of curvature of the aggregates the activation energy increases with an exception in the case of MeOH. The observed results suggest that the long-range transport of charge carriers is less favorable when the aggregates are small and closely packed.

Understanding the regulatory factors of self-assembly processes is a necessity in order to modulate the nano-structures and their properties. Here, the self-assembly mechanism of a peptide-perylenediimide (P-1) conjugate in mixed solvent systems of THF/water is studied and the semiconducting properties are correlated with the morphology. In THF, right handed helical fibers are formed while in 10% THF-water, the morphology changes to nano-rings along with a switch in the helicity to left-handed orientation. Experimental results combined with DFT calculations reveal the critical role of thermodynamic and kinetic factors to control these differential self-assembly processes. In THF, P-1 forms right handed helical fibers in a kinetically controlled fashion. In case of 10% THF-water, the initial nucleation of the aggregate is controlled kinetically. Due to differential solubility of the molecule in these two solvents, elongation of the nuclei into fibers is restricted after a critical length leading to the formation of nano-rings which is governed by the thermodynamics. The helical fibers show superior semi-conducting property to the nano-rings as confirmed by conducting-AFM and conventional I-V characteristics.

A systematic study on the cucurbit[8]uril (CB[8]) assisted transformation of a mixed micellar system of CTAB and a viologen surfactant to vesicles is depicted. The micelle to vesicle transformation is assisted by a charge transfer complex mediated ternary complexation between the viologen group of the surfactant, CB[8], and 2,6-dihydroxynaphthalene. In the presence of CB[8], both the surfactants formed U-shaped binary inclusion complexes inside the CB[8] cavity, and no selective binding is observed. Upon addition of DHN, CB[8] showed two different self-sorting mechanisms. The U-shaped binary complex with CTAB breaks down, and CB[8] moves toward the viologen headgroup of the other surfactant to form a stable ternary complex. In the case of the viologen surfactant, CB[8] moved toward the headgroup leaving the hydrophobic tail free in order to form the ternary complex. The mechanistic detail of this micelle to vesicle transformation is revealed through methodical studies using (1)H and DOSY NMR, ESI-MS, ITC, and other instrumental techniques.