A resorcinarene for inhibition of A? fibrillation.
ABSTRACT: Amyloid-? peptides (A?) fibrillation is the hallmark of Alzheimer's disease (AD). However, it has been challenging to discover potent agents in order to inhibit A? fibrillation. Herein, we demonstrated the effect of resorcinarene on inhibiting A? fibrillation in vitro via experimental and computational methods. A? were incubated with different concentrations of resorcinarene so as to monitor the kinetics by using thioflavin T binding assay. The results, which were further confirmed by far-UV CD spectroscopy and atomic force microscopy, strongly indicated that the higher concentration of resorcinarene, the more effective the inhibition of A? fibrillation. A cytotoxicity study showed that when sea urchin embryos were exposed to the resorcinarene, the majority survived due to the resorcinarene low toxicity. In addition, when the resorcinarene was added, the formation of toxic A? 42 species was delayed. Computational studies of A? fibrillation, including docking simulations and MD simulations, illustrated that the interaction between inhibitor resorcinarene and A? is driven by the non-polar interactions. These studies display a novel strategy for the exploration of promising antiamyloiddogenic agents for AD treatments.
Project description:Amyloid-? peptide (A?) fibrillation is pathologically associated with Alzheimer's disease (AD), and this has resulted in the development of an A? inhibitor which is essential for the treatment of AD. However, the design of potent agents which can target upstream secretases, inhibit A? toxicity and aggregation, as well as cross the blood-brain barrier remains challenging. In, this research carbon dots for AD treatment were investigated in vitro using experimental and computational methods for the first time. The results presented here demonstrate a novel strategy for the discovery of novel antiamyloidogenic agents for AD treatments.
Project description:The antiallergy and potential anticancer drug tranilast has been patented for treating Alzheimer's disease (AD), in which amyloid ?-protein (A?) plays a key pathogenic role. We used solution NMR to determine that tranilast binds to A?40 monomers with ?300 ?M affinity. Remarkably, tranilast increases A?40 fibrillation more than 20-fold in the thioflavin T assay at a 1:1 molar ratio, as well as significantly reducing the lag time. Tranilast likely promotes fibrillation by shifting A? monomer conformations to those capable of seed formation and fibril elongation. Molecular docking results qualitatively agree with NMR chemical shift perturbation, which together indicate that hydrophobic interactions are the major driving force of the A?-tranilast interaction. These data suggest that AD may be a potential complication for tranilast usage in elderly patients.
Project description:A fluorescently labeled resorcinarene cavitand has been successfully embedded in DLPC lipid vesicles and imaged using confocal microscopy. The cavitand resides exclusively in the bilayer.
Project description:The colorimetric properties of resorcinarene solutions had not been investigated since Baeyer's initial synthesis. We recently reported that solutions containing resorcinarene macrocycles develop color upon heating or standing. In the presence of saccharides, these solutions exhibit significant color changes which are easily seen. We herein present strong evidence that the solution color is due to macrocycle ring opening and oxidation. The optical responses to saccharides are due to complexation of the sugar with the acyclic chromophores. We apply these mechanistic insights toward the challenging problem of the visual detection of neutral oligosaccharides by simple chromogens. In addition, we also report the first single-crystal X-ray crystal structure determination of a rarely observed "diamond" resorcinarene stereoisomer.
Project description:Pyrophosphate (PPi) is a byproduct of DNA and RNA synthesis, and abnormal levels are indicative of disease. We report the high-affinity binding of PPi in water by N-alkyl ammonium resorcinarene chloride receptors. Experimental analysis using 1H and 31P NMR, isothermal titration calorimetry, mass spectrometry, and UV-vis spectroscopy all support exceptional selectivity of these systems for PPi in water. The measured affinity of K1 = 1.60 × 107 M-1 for PPi is three orders of magnitude larger than that observed for binding to another phosphate, ATP. This exceptional anion-binding affinity in water is explored through a detailed density functional theory computational study. These systems provide a promising avenue for the development of future innovative medical diagnostic tools.
Project description:Protein misfolding is interrelated to several diseases, including neurodegenerative diseases and type?II diabetes. Misfolded/unfolded proteins produce soluble oligomers that accumulate into "amyloid plaques". Inhibition of amyloid-plaque formation by those misfolded/unfolded proteins will lead to the invention of new therapeutic approaches for amyloid-related diseases. Herein, methylene blue (MB), a well-defined drug against multiple diseases and disorders, is used to impede insulin fibrillation. In this study, we perform an array of in?vitro experiments to monitor the effects of MB on the fibrillation of bovine insulin. Our results confirm that MB distresses the kinetics of insulin fibrillation by interacting with insulin in its monomeric form. A thioflavin?T assay indicates that insulin fibrillation is interrupted upon the addition of MB. The same results are confirmed by circular dichroism, dynamic light scattering (DLS), and size-exclusion chromatography (SEC). According to the DLS data, the insulin fibrils are 800?nm in diameter, and the addition of MB reduces the size of the fibrils, which remain 23?nm in size, and this indicates that no fibrillation of insulin occurs in the presence of MB. This data is also supported by SEC. Saturation transfer difference NMR spectroscopy and molecular dynamics simulations demonstrate the interactions between insulin and MB at the atomic level.
Project description:Amyloid are protein aggregates formed by cross ? structures assemblies. Inhibiting amyloid aggregation or facilitating its disassembly are considered to be two major effective therapeutic strategies in diseases involving peptide or protein fibrillation such Alzheimer's disease or diabetes. Using thioflavin-T fluorescence, far-UV circular dichroism spectroscopy, and atomic force microscopy, we found nontoxic and biocompatible black phosphorus quantum dots (BPQDs) appear to have an exceptional capacity to inhibit insulin aggregation and to disassemble formed mature fibrils, even at an ultralow concentration (100 ng/mL). The inhibition of fibrillation persists at all stages of insulin aggregation and increases PC12 cells survival when exposed to amyloid fibrils. Molecular dynamics simulations suggest that BPQDs are able to stabilize the ?-helix structure of insulin and obliterate the ?-sheet structure to promote the fibril formation. These characteristics make BPQDs be promising candidate in preventing amyloidosis, disease treatment, as well as in the storage and processing of insulin.
Project description:Reactions of glycidyl methacrylate with the crown and chair conformers of tetra(4-hydroxyphenyl)calixresorcinarene were studied. The reactions were done over epoxide groups present in the ester, which can easily undergo an opening reaction with hydroxyl groups in the macrocyclic system. Initially, epoxidation reactions were carried out with pure conformers, and it was observed that the reaction between tetra(4-hydroxyphenyl)calixresorcinarene fixed in the chair conformation does not occur, while for the molecule fixed in the crown conformation only one tetraalkylated derivative was obtained. The obtained product was characterized using IR, ¹H-NMR, 13C-NMR, COSY, HMQC and HMBC techniques. An exhaustive NMR study showed that the reaction is selective at the hydroxyl groups in the lower rim, without affecting the hydroxyl groups in the upper rim. In addition, the RP-HPLC analysis of the epoxidation reaction mixture, using both crown and chair conformers, showed that only the crown conformer reacted under tested conditions. Finally, a comparative study of the reactivity of tetranonylcalixresorcinarene with glycidyl methacrylate showed that the reaction does not take place. Instead, the formation of the tetranonylcalixresorcinarene tetrasodium salt was observed, which confirms that the hydroxyl groups in the upper rim are unreactive under these conditions.
Project description:The closely related, self-assembled resorcinarene and pyrogallolarene capsules display contrasting and puzzling encapsulation behaviors. Herein, we elucidate the reasons for these differences by combining experimental studies and DFT calculations. Furthermore, we report that, in contrast to the resorcinarene capsule, the pyrogallolarene derivative is not capable of catalyzing reactions with cationic transition states. The molecular mechanisms responsible for these observations are probed in detail.
Project description:As a membrane-mimetic system, detergent micelles are popularly used to extract membrane proteins from lipid environments and to maintain their solubility and stability in an aqueous medium. However, many membrane proteins encapsulated in conventional detergents tend to undergo structural degradation during extraction and purification, thus necessitating the development of new agents with enhanced properties. In the current study, two classes of new amphiphiles are introduced, resorcinarene-based glucoside and maltoside amphiphiles (designated RGAs and RMAs, respectively), for which the alkyl chains are facially segregated from the carbohydrate head groups. Of these facial amphiphiles, two RGAs (RGA-C11 and RGA-C13) conferred markedly enhanced stability to four tested membrane proteins compared to a gold-standard conventional detergent. The relatively high water solubility and micellar stability of the RGAs compared to the RMAs, along with their generally favourable behaviours for membrane protein stabilisation described here, are likely to be, at least in part, a result of the high conformational flexibility of these glucosides. This study suggests that flexibility could be an important factor in determining the suitability of new detergents for membrane protein studies.