CTAB/water/chloroform reverse micelles: a closed or open association model?

The micellization of cetyltrimethylammonium bromide (CTAB) in chloroform in the presence of water was examined. Three scenarios of the reverse micelle formation, the closed, open and Eicke's association models, were considered in the interpretation of the experimental data. The growth of the aggregates was observed through the changes of NMR signals of associated water, probing the microenvironment of the premicellar aggregates and the interior of reverse micelles. This technique if combined with isothermal titration calorimetry (ITC) revealed that hydrated surfactant premicellar aggregates are already present at ∼6 mM CTAB. NMR, ITC and conductometry were used to determine the critical micelle concentration (cmc) to be ∼40 mM CTAB. It is suggested that the variation of the cmc values reflects the fact that the NMR analysis indicated the beginning of the reverse micelle formation, whereas conductometry and ITC measurements provided the upper limit and an average value of a so-called apparent cmc, respectively. The cmc values were found to be unaffected by the water content. The presence of reverse micelles, the existence of multiple equilibria, and high polydispersity of the samples were evidenced by DOSY NMR spectroscopy. As a result, we validated Eicke's association model, according to which cyclic inverse micelles are formed by a structural reorganization of linear associates within a narrow concentration range, called the apparent cmc. New experimental results have also been gained for micellization of cetyltrimethylammonium chloride (CTAC) in chloroform in the presence of water; a similar mechanism of reverse micelle formation has been suggested.

Streamlined single-molecule RNA-FISH of core clock mRNAs in clock neurons in whole mount Drosophila brains.

Circadian clocks are ∼24-h timekeepers that control rhythms in almost all aspects of our behavior and physiology. While it is well known that subcellular localization of core clock proteins plays a critical role in circadian regulation, very little is known about the spatiotemporal organization of core clock mRNAs and its role in generating ∼24-h circadian rhythms. Here we describe a streamlined single molecule Fluorescence In Situ Hybridization (smFISH) protocol and a fully automated analysis pipeline to precisely quantify the number and subcellular location of mRNAs of Clock, a core circadian transcription factor, in individual clock neurons in whole mount Drosophila adult brains. Specifically, we used ∼48 fluorescent oligonucleotide probes that can bind to an individual Clock mRNA molecule, which can then be detected as a diffraction-limited spot. Further, we developed a machine learning-based approach for 3-D cell segmentation, based on a pretrained encoder-decoder convolutional neural network, to automatically identify the cytoplasm and nuclei of clock neurons. We combined our segmentation model with a spot counting algorithm to detect Clock mRNA spots in individual clock neurons. Our results demonstrate that the number of Clock mRNA molecules cycle in large ventral lateral clock neurons (lLNvs) with peak levels at ZT4 (4 h after lights are turned on) with ∼80 molecules/neuron and trough levels at ZT16 with ∼30 molecules/neuron. Our streamlined smFISH protocol and deep learning-based analysis pipeline can be employed to quantify the number and subcellular location of any mRNA in individual clock neurons in Drosophila brains. Further, this method can open mechanistic and functional studies into how spatiotemporal localization of clock mRNAs affect circadian rhythms.

Unusual evolution in Wegener's granulomatosis: recovery of pulmonary involvement while renal disease progressed to end-stage.

A 54-year-old male patient was admitted for acute respiratory distress with fever. He was suffering from chronic sinusitis/rhinitis and had persistent otitis for the past 2 months before admission despite several antibiotics courses. He developed a complex pulmonary involvement (embolism and diffuse alveolar hemorrhage) with acute glomerular disease (proteinuria and hematuria but initially no renal failure). Clinical suspicion of Wegener's granulomatosis was confirmed by the positive high titer of antineutrophil cytoplasmic antibodies (c-ANCA with antiproteinase 3 specificity) and despite a negative nasal biopsy. Treatment including cyclophosphamide and methylprednisolone intravenous pulses permitted pulmonary recovery over 4 weeks contrasting with the development of rapidly progressive glomerulonephritis and polyneuropathy of lower limbs. Renal biopsy showed pauci-immune crescentic and necrotizing glomerulonephritis. However, despite additional plasma exchanges, acute kidney injury worsened and the patient ended up in dialysis. Such a dissociated evolution was unexpected in this case since pulmonary and renal involvements reflected the same pathological process (small vessels vasculitis/capillaritis) and the same pathogenic mechanism (antiproteinase 3 autoantibodies).

Enhanced photocatalytic activity of gold nanoparticles driven by supramolecular host-guest chemistry.

Functionalization of gold nanoparticles with supramolecular hosts allows their plasmon-based photocatalytic activity to be enhanced. This is mainly ascribed to the formation of labile host-guest complexes with the reagent molecules on the metal surface, thus promoting nanoparticle-substrate approximation without interfering with the light-induced catalytic process.