Probing Intermolecular Interactions within the Amyloid ß Trimer Using a Tethered Polymer Nanoarray.

Amyloid oligomers are considered the most neurotoxic species of amyloid aggregates. Spontaneous assembly of amyloids into aggregates is recognized as a major molecular mechanism behind Alzheimer's disease and other neurodegenerative disorders involving protein aggregation. Characterization of such oligomers is extremely challenging but complicated by their transient nature. Previously, we introduced a flexible nanoarray (FNA) method enabling us to probe dimers assembled by the amyloid ß (14-23) [Aß (14-23)] peptide. The study presented herein modifies and enhances this approach to assemble and probe trimers of Aß (14-23). A metal-free click chemistry approach was used, in which dibenzocyclooctyne (DBCO) groups were incorporated at selected sites within the FNA template to click Aß (14-23) monomers at their terminal azide groups. Atomic force microscopy (AFM) force spectroscopy was employed to characterize the assemblies. The force measurement data demonstrate that the dissociation of the trimer undergoes a stepwise pattern, in which the first monomer dissociates at the rupture force ∼48 ± 2.4 pN. The remaining dimer ruptures at the second step at a slightly larger rupture force (∼53 ± 3.2 pN). The assembled trimer was found to be quite dynamic, and transient species of this inherently dynamic process were identified.

A dipodal bimane-ditriazole-diCu(II) complex serves as an ultrasensitive water sensor.

An ultrasensitive fluorescent water sensor based on a dipodal bimane-Cu(II) complex is reported here. This complex, which is non-fluorescent in the absence of water, demonstrates a remarkable turn-on fluorescence in the presence of extremely low (0.000786% v/v) concentrations of water, via highly selective water-induced displacement of copper and restoration of the innate bimane fluorescence.

Highly Sensitive Water Detection Through Reversible Fluorescence Changes in a syn-Bimane Based Boronic Acid Derivative.

Reported herein is a fluorometric and colorimetric sensor for the presence of trace amounts of water in organic solvents, using syn-bimane based boronate ester 1. This sensor responds to the presence of water with a highly sensitive turn-off fluorescence response, with detection limits as low as 0.018% water (v/v). Moreover, analogously high performance was observed when compound 1 was adsorbed on filter paper, with the paper-based sensor responding both to the presence of liquid water and to humid atmospheres. Reusability of the paper-based sensor up to 11 cycles was demonstrated, albeit with progressive decreases in the performance, and 1H NMR and mass spectrometry analyses were used to explain the observed, hydrolysis-based sensor response.

Sonication-Induced, Solvent-Selective Gelation of a 1,8-Napthalimide-Conjugated Amide: Structural Insights and Pollutant Removal Applications.

Reported herein is the synthesis, characterization, and dye removal applications of a highly solvent-selective organogel-forming amide, compound 1, which contains a 1,8-naphthalmide moiety, flexible n-hexyl chain, and benzene ring. This compound displayed remarkable solvent selectivity, with gel formation occurring only in the presence of alkylated aromatic solvents. Detailed structural characterization of the gels, combined with notable theoretical insights, is invoked to explain the highly selective gelation properties of compound 1, as is a comparison to non-gel forming structural isomer 2, which contains the same structural elements in a different arrangement. Finally, the ability of the gel derived from compound 1 to act as a reusable material for the efficient removal of cationic organic dyes from contaminated aqueous environments is also reported, with up to 11 repeated uses of the gel still maintaining the ability to effectively remove Rhodamine B.

Highly sensitive detection of cobalt through fluorescence changes in ß-cyclodextrin-bimane complexes.

A supramolecular complex of syn-(methyl,methyl)bimane (1) and ß-cyclodextrin demonstrates a sensitive (limit of detection = 0.60 nM) and selective fluorescence turn-off response in the presence of cobalt in aqueous media, with calibration curves enabling quantitation in solution and using filter papers on which bimane and cyclodextrin were adsorbed. 1H NMR spectroscopy provides insight into interactions underlying the sensor performance.

On-line Ammonia Sensor and Invisible Security Ink by Fluorescent Zwitterionic Spirocyclic Meisenheimer Complex.

Ammonia is not only a highly important gas for civilization but also contribute significantly for climate change and human health hazard. Highly sensitive ammonia sensor has been developed from a fluorescent zwitterionic spirocyclic Meisenheimer complex. Moreover, formation of this Meisenheimer complex can also be utilized for selective as well as naked eye instant detection of nitro aromatic explosive picric acid. The presence of a quaternary nitrogen atom directly attached to the spiro carbon is the unique feature of this Meisenheimer complex. This excellent photoluminescent (PL) Meisenheimer complex has two distinct stimuli responsive sites. One is sensitive towards acid while the other one is towards the base. These two positions can be modulated by adding one equivalent acid and one equivalent base to result two new products which are non fluorescent. One of these two non fluorescent species was found very exciting because of its UV/Vis transparency. Utilizing this concept we have fabricated an on-line sensor for measuring ammonia in dry or humid and condensing sewer air. The sensor was robust against ambient temperature and humidity variation. We have also developed an invisible ink from this Meisenheimer complex, with potential application for security purpose.

Halogen bond induced phosphorescence of capped γ-amino acid in the solid state.

The Boc and N,N'-dicyclohexylurea capped γ-amino acid upon monobromination showed phosphorescence in the solid state. The compound exhibited different photoluminescence intensity and lifetimes in crystals obtained from ethyl acetate and methanol. X-ray crystallography revealed that the intermolecular C=O…Br halogen bond directs the heavy atom effect to produce the phosphorescence.

Case report of two sisters suffering from Weill-Marchesani syndrome with pulmonary stenosis.

We report two sisters having a rare congenital anomaly-Weill-Marchesani syndrome having disproportionate short height, restriction of joint movements, brachydactyly, dislocation of lens, bilateral glaucomatous optic atrophy, and pulmonary stenosis.

Cryptogenic cirrhosis: metabolic liver disease due to insulin resistance.

OBJECTIVE: Etiopathogenesis of cryptogenic cirrhosis (CC) is not yet well established. Up to 20% of non-alcoholic fatty liver disease (NAFLD) may progress to cirrhosis, mostly termed as cryptogenic. Insulin resistance and altered metabolic parameters form a major pathogenic link between NAFLD and CC. CC may thus be actually a metabolic liver disease. MATERIALS AND METHODS: Thirty-four patients of CC and 32 patients having cirrhosis due to chronic hepatitis B (Hep B) were assessed in a cross-sectional study in a tertiary hospital for insulin resistance, % ß-cell activity, obesity indices, plasma glucose, lipid profiles, and many other parameters. RESULTS: CC patients had higher homeostasis model assessment (HOMA)-IR compared to Hep B group (P = 0.000016). A positive correlation between IR values and Child-Pugh score among CC patients was found ("r" = 0.87; P < 0.00001). Out of 34 CC patients, 15 (44.1%) had obesity contrary to 6 (18.8%) in the control group (P = 0.0022). Differences were observed in subcutaneous fat (P = 0.0022), intra-abdominal fat (P = 0.0055), waist circumference (P = 0.014), and percentage body fat (P = 0.047) between the two groups. Significant differences were observed in the levels of triglyceride, total cholesterol, and very low density lipoprotein (VLDL). CONCLUSION: Most of the CC patients showed significantly higher prevalence of HOMA-IR, obesity indices, and various parameters of "lipotoxicity" and metabolic syndrome, suggesting that CC may be the long-term consequence of a type of "metabolic liver disease." Further studies are required to evaluate the role of therapeutic interventions to enhance insulin sensitivity in such patients.