Protometabolic Reduction of NAD with α-Keto Acids.

Deciphering the origins of the chemistry that supports life has frequently centered on determining prebiotically plausible paths that produce the molecules found in biology. What has been less investigated is how the energy released from the breakdown of foodstuff is coupled to the persistence of the protocell. To gain better insight into how such coupled chemistry could have emerged prebiotically, we probed the reactivity of the ribodinucleotide NAD with small organic molecules that were previously identified as potential constituents of protometabolism.

Luminescent Naphthalene Diimide-Based Peptide in Aqueous Medium and in Solid State: Rewritable Fluorescent Color Code.

This study convincingly demonstrates a unique example of the self-assembly of a naphthalene diimide (NDI)-appended peptide into a fluorescent J-aggregate in aqueous media. Moreover, this aggregated species shows a remarkable yellow fluorescence in solid state, an unusual phenomenon for NDI-based compounds. The aggregated species has been characterized using transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy, X-ray diffraction, time-correlated single proton counting (TCSPC), UV-vis, and photoluminescence studies.

Ag -Induced Switching of DNA Binding Modes via Formation of a Supramolecular Metallacycle.

The histidine derivative L1 of the DNA intercalator naphthalenediimide (NDI) forms a triangular Ag complex (C2). The interactions of L1 and of C2 with DNA were studied by circular dichroism (CD) and UV/Vis spectroscopy and by viscosity studies. Different binding modes were observed for L1 and for C2, as the Ag complex C2 is too large in size to act as an intercalator.

A Ferrocene-Tryptophan Conjugate: The Role of the Indolic Nitrogen in Supramolecular Assembly.

Bio-organometallic ferrocene-containing amino acids and peptides have been reported to form gels and are interesting to study due to their structural properties and applications for biological purposes. In this study, a ferrocene-dicarboxylic acid derivative of the dipeptide tryptophan-tryptophan was investigated. The indolic nitrogen in the amino acid tryptophan is important for biological functions due to its role in hydrogen bonding.

On the Role of Chirality in Guiding the Self-Assembly of Peptides.

Homochirality in peptides is crucial in sustaining "like-like" intermolecular interactions that allow the formation of assemblies and aggregates and is ultimately responsible for the resulting material properties. With the help of a series of stereoisomers of the tripeptide F-F-L, we demonstrate the critical role that peptide stereochemistry plays in the self-assembly of peptides, guided by molecular recognition, and for self-sorting. Homochiral self-assemblies are thermally and mechanically more robust compared to heterochiral self-assemblies.

A tripeptide-based self-shrinking hydrogel for waste-water treatment: removal of toxic organic dyes and lead (Pb) ions.

A triphenylalanine-based superhydrogel shows automatic syneresis (self-compressing properties) with time and this self-shrinking behavior has been successfully utilized to remove toxic lead ions and organic dyes from waste-water efficiently with the ability to re-use for a few times.

Metal coordination of ferrocene-histidine conjugates.

This study presents a few bis(histidine) ligands working to build a small peptidic model system of zinc structural sites. Ferrocene-peptide conjugates Fc[CO-His(Trt)-His(Trt)-OMe] (3), Fc[CO-His(Trt)-Asp(OMe)-OMe] (4), and Fc[CO-His(Trt)-Glu(OMe)-OMe] (5) were synthesized and characterized spectroscopically. H-NMR and IR spectroscopic studies reveal hydrogen bonding interactions and while more detailed circular dichroism studies show a 1,2'-P helical "Herrick conformation" for Fc-conjugates 4 and 5, we discovered M-helical chirality in Fc-peptide 3.

Two-Component Fluorescent-Semiconducting Hydrogel from Naphthalene Diimide-Appended Peptide with Long-Chain Amines: Variation in Thermal and Mechanical Strengths of Gels.

Two-component fluorescent hydrogels have been discovered, containing the mixtures of naphthalene diimide (NDI)-conjugated peptide-functionalized bola-amphiphile and primary amines with long alkyl chains at physiological pH 7.46. The aggregation-induced enhanced emission associated with an NDI-appended peptide in aqueous medium is rare, as water is known to be a good quencher of fluorescence.

Peptide based hydrogels for cancer drug release: modulation of stiffness, drug release and proteolytic stability of hydrogels by incorporating d-amino acid residue(s).

Synthetic tripeptide based noncytotoxic hydrogelators have been discovered for releasing an anticancer drug at physiological pH and temparature. Interestingly, gel stiffness, drug release capacity and proteolytic stability of these hydrogels have been successfully modulated by incorporating d-amino acid residues, indicating their potential use for drug delivery in the future.

Fluorescence from an H-aggregated naphthalenediimide based peptide: photophysical and computational investigation of this rare phenomenon.

Fluorescence associated with J-aggregated naphthalenediimides (NDIs) is common. However, in this study an NDI based synthetic peptide molecule is found to form a fluorescent H-aggregate in a chloroform (CHCl3)-methylcyclohexane (MCH) mixture. An attempt has been made to explain the unusual fluorescence property of this H-aggregated NDI derivative.

Time-dependent gel to gel transformation of a peptide based supramolecular gelator.

A dipeptide with a long fatty acid chain at its N-terminus gives hydrogels in phosphate buffer in the pH range 7.0-8.5.

Tailor-made design of J- or H-aggregated naphthalenediimide-based gels and remarkable fluorescence turn on/off behaviour depending on solvents.

A naphthalenediimide (NDI)-based new gelator molecule has been discovered, the molecule forms interesting J/H-aggregated species depending on solvents (aliphatic/aromatic) and remarkably, the fluorescence of the gel phase materials is nicely tuned according to the electron donating capacity of the aromatic solvent.

Selective binding of hydrogen chloride and its trapping through supramolecular gelation.

A pyridine containing amino acid based gelator forms gel in aqueous media in the presence of hydrochloric acid and the chloride ion is found to be very selective for gelation. The gelator is successfully applied for the detection and trapping of hydrogen chloride gas and this indicates its probable application for removing hazardous HCl gas from the environment.

Charge-transfer complex formation in gelation: the role of solvent molecules with different electron-donating capacities.

A naphthalenediimide (NDI)-based synthetic peptide molecule forms gels in a particular solvent mixture (chloroform/aromatic hydrocarbon, 4:1) through charge-transfer (CT) complex formation; this is evident from the corresponding absorbance and fluorescence spectra at room temperature. Various aromatic hydrocarbon based solvents, including benzene, toluene, xylene (ortho, meta and para) and mesitylene, have been used for the formation of the CT complex. The role of different solvent molecules with varying electron-donation capacities in the formation of CT complexes has been established through spectroscopic and computational studies.

Multi-stimuli responsive self-healing metallo-hydrogels: tuning of the gel recovery property.

A series of amphiphilic tyrosine based self-healable, multi-stimuli responsive metallo-hydrogels have been discovered. Formation of these hydrogels is highly selective to Ni(2+) ions. The self-healing property and the stiffness of these metallo-hydrogels can be tuned by varying the chain length of the corresponding gelator amphiphile.

Assembly of naphthalenediimide conjugated peptides: aggregation induced changes in fluorescence.

Naphthalenediimide appended peptide based self-assembly was studied. Interestingly, an aggregation induced drastic change in the fluorescence property and gel formation were observed depending on the solvent composition (chloroform : methylcyclohexane) at a fixed concentration of 1.6 mM at room temperature.

Formation of hybrid hydrogels consisting of tripeptide and different silver nanoparticle-capped ligands: modulation of the mechanical strength of gel phase materials.

An N-terminally Boc (tert-butyloxycarbonyl) group-protected synthetic tripeptide (Boc-Phe-Phe-Ala-OH) has been found to form a translucent hydrogel in basic aqueous medium. This hydrogel material has been characterized using field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy, differential scanning calorimetric, X-ray diffraction (XRD), and rheological studies. FE-SEM and TEM studies have revealed the formation of a nanofibrillar network structure upon gelation.