Solvent-controlled self-assembly of Fmoc protected aliphatic amino acids.

Self-assembly of modified amino acids facilitate the formation of various structures that have unique properties and therefore serve as excellent bio-organic scaffolds for diverse applications. Self-assembly of Fmoc protected single amino acids has attracted great interest owing to their ease of synthesis and applications as functional materials. Smaller assembly units enable synthetic convenience and potentially broader adoption.

An Isothiazolanthrone-Based Self-Assembling Anticancer Color-Changing Dye for Concurrent Imaging and Monitoring of Cell Viability.

We report the photophysical properties, self-assembly and biological evaluation of an isothiazolanthrone-based dye, 7-amino-6H-anthra[9,1-cd]isothiazol-6-one (AAT), which reveals anticancer properties and can be potentially used as dye for monitoring cell viability. The solvent-dependent photophysical studies suggest that the emission of AAT is sensitive to environment polarity due to which interesting changes in the colored emission may be observed owing to the charge transfer (CT) processes. AAT also self-assembles to tree-like branched morphologies and produce, a greenish emission inside the cells when imaged after short interval (15 mins) of incubation while a red fluorescence could be noted after 24 h.

A new aggregation induced emission enhancement (AIEE) dye which self-assembles to panchromatic fluorescent flowers and has application in sensing dichromate ions.

We report for the very first time the crystal structure and self-assembly of a new aggregation-induced emission enhancement (AIEE) dye 4-(5-methoxythiazolo[4,5-]pyridin-2-yl)-,-dimethylaniline (TPA) and its application in sensing dichromate ions. TPA reveals cyan blue emission under UV and visible light. The self-assembly properties of TPA were studied extensively by scanning electron microscopy (SEM) which revealed the formation of beautiful flower-like morphologies.

Unusual Aggregates Formed by the Self-Assembly of Proline, Hydroxyproline, and Lysine.

There is a plethora of significant research that illustrates toxic self-assemblies formed by the aggregation of single amino acids, such as phenylalanine, tyrosine, tryptophan, cysteine, and methionine, and their implication on the etiology of inborn errors of metabolisms (IEMs), such as phenylketonuria, tyrosinemia, hypertryptophanemia, cystinuria, and hypermethioninemia, respectively. Hence, studying the aggregation behavior of single amino acids is very crucial from the chemical neuroscience perspective to understanding the common etiology between single amino acid metabolite disorders and amyloid diseases like Alzheimer's and Parkinson's. Herein we report the aggregation properties of nonaromatic single amino acids l-proline (Pro), l-hydroxyproline (Hyp), and l-lysine hydrochloride (Lys).

Chemical Perspective of the Mechanism of Action of Antiamyloidogenic Compounds Using a Minimalistic Peptide as a Reductionist Model.

The diphenylalanine (FF) residue which is present at the 19 and 20 positions of the amyloid beta (1-42) (Aβ42) peptide sequence is considered as a reductionist model for studying Aβ42 aggregation. FF self-assembles into well-ordered tubular structures via aromatic π-π stacking. Herein the manuscript, we have presented a chemical perspective on the mechanism of action of antiamyloid compounds by assessing their interaction with FF.

Sequential and cellular detection of copper and lactic acid by disaggregation and reaggregation of the fluorescent panchromatic fibres of an acylthiourea based sensor.

We report, for the first time, the self-assembly of an acyl-thiourea based sensor, N-{(6-methoxy-pyridine-2-yl) carbamothioyl}benzamide (NG1), with panchromatic fluorescent fibres and its dual-sensing properties for the sequential detection of Cu2+ ions and lactic acid. The panchromatic fibres formed by NG1 were disrupted in the presence of Cu2+ ions and this was accompanied by a visible colour change in the solution from colourless to yellow. The addition of lactic acid to the NG1 + Cu2+ solution, on the other hand, induced re-aggregation to fibrillar structures and the colour of the solution again changed to colourless.

Synthesis and Aggregation Studies of a Pyridothiazole-Based AIEE Probe and Its Application in Sensing Amyloid Fibrillation.

We report the aggregation and photophysical properties of a pyridothiazole-based, aggregation-induced, emission-enhancement (AIEE) luminogen 4-(5-methoxy-thiazolo[4,5-]pyridin-2-yl)benzoic acid (PTC1) and its application for the sensitive detection and monitoring of amyloid fibrillation. The aggregation properties of the AIEE probe were extensively studied by atomic force microscopy (AFM) and dynamic light scattering (DLS), and it was noted that as aggregation increases the fluorescence of PTC1 also was increased. The fluorescence of PTC1 was quenched upon the addition of cupric (Cu) ions, while the fluorescence is regenerated in the presence of amyloid fibers.

Amyloid-like Structures Formed by Single Amino Acid Self-Assemblies of Cysteine and Methionine.

We report for the very first time the discovery of amyloid-like self-assemblies formed by the nonaromatic single amino acids cysteine (Cys) and methionine (Met) under neutral aqueous conditions. The structure formation was assessed and characterized by various microscopic and spectroscopic techniques such as optical microscopy, phase contrast microscopy, scanning electron microscopy, and transmission electron microscopy. The mechanism of self-assembly and the role of hydrogen bonding and thiol interactions of Cys and Met were assessed by Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and solid state NMR along with various control experiments.