Spatiotemporal multicolor labeling of individual cells using peptide-functionalized quantum dots and mixed delivery techniques

Multicolor fluorescent labeling of both intra- and extracellular structures is a powerful technique for simultaneous monitoring of multiple complex biochemical processes. This approach remains extremely challenging, however, as it often necessitates the combinatorial use of numerous targeting probes (e.g., antibodies), multistep bioconjugation chemistries, different delivery strategies (e.g., electroporation or transfection reagents), cellular fixation coupled with membrane permeabilization, and complex spectral deconvolution. Here, we present a nanoparticle-based fluorescence labeling strategy for the multicolor labeling of distinct subcellular compartments within live cells without the need for antibody conjugation or cellular fixation/permeabilization. This multipronged approach incorporates an array of delivery strategies, which localize semiconductor quantum dots (QDs) to various subcellular structures. QD uptake is implemented in a spaciotemporal manner by staggering the delivery of QD-peptide composites and exploiting various innate (peptide-mediated endocytosis, peptide-membrane interaction, polymer-based transfection) along with physical (microinjection) cellular delivery modalities to live cells growing in culture over a 4 day period. Imaging of the different intracellular labels is simplified by the unique photophysical characteristics of the QDs in combination with Fo?rster resonance energy transfer sensitization, which allow for multiple spectral windows to be accessed with one excitation wavelength. Using this overall approach, QDs were targeted to both early and late endosomes, the cellular cytosol, and the plasma membrane in live cells, ultimately allowing for simultaneous five-color fluorescent imaging.     

Cyclopropenylidene carbene ligands in palladium catalysed coupling reactions: carbene ligand rotation and application to the Stille reaction

Reaction of [Pd(PPh(3))(4)] with 1,1-dichloro-2,3-diarylcyclopropenes gives complexes of the type cis-[PdCl(2)(PPh(3))(C(3)(Ar)(2))] (Ar = Ph 5, Mes 6). Reaction of [Pd(dba)(2)] with 1,1-dichloro-2,3-diarylcyclopropenes in benzene gave the corresponding binuclear palladium complexes trans-[PdCl(2)(C(3)(Ar)(2))](2) (Ar = Ph 7, p-(OMe)C(6)H(4)8, p-(F)C(6)H(4)9). Alternatively, when the reactions were performed in acetonitrile, the complexes trans-[PdCl(2)(NCMe)(C(3)(Ar)(2))] (Ar = Ph 10, p-(OMe)C(6)H(4)11 and p-(F)C(6)H(4)) 12) were isolated. Addition of phosphine ligands to the binuclear palladium complex 7 or acetonitrile adducts 11 and 12 gave complexes of the type cis-[PdCl(2)(PR(3))(C(3)(Ar)(2))] (Ar = Ph, R = Cy 13, Ar = p-(OMe)C(6)H(4), R = Ph 14, Ar = p-(F)C(6)H(4), R = Ph 15). Crystal structures of complexes 6·3.25CHCl(3), 10, 11·H(2)O and 12-15 are reported. DFT calculations of complexes 10-12 indicate the barrier to rotation about the carbene-palladium bond is very low, suggesting limited double bond character in these species. Complexes 5-9 were tested for catalytic activity in C-C coupling (Mizoroki-Heck, Suzuki-Miyaura and, for the first time, Stille reactions) and C-N coupling (Buchwald-Hartwig amination) showing excellent conversion with moderate to high selectivity.     

Octanuclear gold(I) alkynyl-diphosphine clusters showing thermochromic luminescence

The unprecedented, purely gold(I) alkynyl-diphosphine clusters 1-3 demonstrate intense room-temperature phosphorescence with maximum quantum efficiency of 92% in solution (3) and 86% in solid (2) and thermally dependent emission in the crystalline form, attributed to the crystal lattice arrangement.     

Five isomers of monomeric cytosine and their interconversions induced by tunable UV laser light

Photoisomerization processes involving five isomers of cytosine were induced by narrowband tunable UV irradiation of matrix-isolated monomers of the compound. Irradiation of an argon matrix containing cytosine monomers with UV λ = 313 nm laser light resulted in syn?anti photoisomerizations between the two imino-oxo forms, whereas the substantially more populated amino-hydroxy and amino-oxo forms stayed intact. Subsequent irradiation with shorter-wavelength UV λ = 311 nm laser light led to two concomitant phototautomeric processes consuming the amino-oxo isomer: (i) an oxo → hydroxy hydrogen-atom transfer photoprocess converting the amino-oxo form into the amino-hydroxy tautomer; (ii) amino → imino hydrogen-atom transfer converting the amino-oxo form into the imino-oxo isomers. The UV-induced phototransformations, together with mutual conversions of the two amino-hydroxy conformers induced by irradiation with narrowband NIR light, allowed positive detection and identification of the five isomeric forms of monomeric cytosine. This is the first experimental observation of all five low-energy isomers of cytosine.     

Determination of submillimolar concentration of ferrate(VI) in alkaline solutions by amperometric titration

A new amperometric titration method was developed for quantitative determination of ferrate(VI) (Fe^VIO₄ ²⁻) in the 7.06×10⁻⁵−5.73×10⁻³ M concentration range. Chromium(III) hydroxide solution was used as the titrant. The diffusion current (Id) had a linear relationship with the concentration of ferrate(VI) and slopes were dependent on the concentration of NaOH. The amperometric titration could detect a lower concentration of ferrate(VI) than could potentiometric and colorimetric titrations. The method was applied successfully to determine concentrations of ferrate(VI), generated electrochemically, in strong alkaline solutions.      

Thermal analysis of salts from 4-nitrophenol and aliphatic amines

In this work, the thermodynamic performance of a single slope solar still with cotton cloth energy storage medium was compared with a simple solar still without energy storage. Two solar stills with similar dimensions (one with cotton cloth energy storage and another without energy storage) were fabricated and investigated its performance under the hot humid climatic conditions of Chennai in India during the summer months of 2017. The performance was evaluated in terms of energy and exergy analysis based on first and second law of thermodynamics, respectively, for 2 mm, 4 mm, 6 mm and 8 mm cotton cloth thickness. The results showed that the maximum energy and exergy efficiency of a solar still was observed to be 23.8% and 2.6%, respectively, for 6 mm cotton cloth thickness. The results confirmed that the cotton cloth regenerative medium has enhanced the still productivity by about 24.1% when compared to the solar still without heat storage.

     

Hierarchical Metal Sulfide/Carbon Spheres: A Generalized Synthesis and High Sodium‐Storage Performance

The development of suitable anode materials is far from satisfactory and is a major scientific challenge for a competitive sodium‐ion battery technology. Metal sulfides have demonstrated encouraging results, but still suffer from sluggish kinetics and severe capacity decay associated with the phase change. Herein we show that rational electrode design, that is, building efficient electron/ion mixed‐conducting networks, can overcome the problems resulting from conversion reactions. A general strategy for the preparation of hierarchical carbon‐coated metal sulfide (MS?C) spheres through thermal sulfurization of metal glycerate has been developed. We demonstrate the concept by synthesizing highly uniform hierarchical carbon coated vanadium sulfide (V₂S₃?C) spheres, which exhibit a highly reversibly sodium storage capacity of 777 mAh g^?1 at 100 mA g^?1, excellent rate capability (410 mAh g^?1 at 4000 mA g^?1), and impressive cycling ability.     

Dynamic Nuclear Polarization of 13C Nuclei in the Liquid State over a 10 Tesla Field Range

Nuclear magnetic resonance (NMR) techniques play an essential role in natural science and medicine. In spite of the tremendous utility associated with the small energies detected, the most severe limitation is the low signal‐to‐noise ratio. Dynamic nuclear polarization (DNP), a technique based on transfer of polarization from electron to nuclear spins, has emerged as a tool to enhance sensitivity of NMR. However, the approach in liquids still faces several challenges. Herein we report the observation of room‐temperature, liquid DNP ¹³C signal enhancements in organic small molecules as high as 600 at 9.4 Tesla and 800 at 1.2 Tesla. A mechanistic investigation of the ¹³C‐DNP field dependence shows that DNP efficiency is raised by proper choice of the polarizing agent (paramagnetic center) and by halogen atoms as mediators of scalar hyperfine interaction. Observation of sizable DNP of ¹³CH₂ and ¹³CH₃ groups in organic molecules at 9.4 T opens perspective for a broader application of this method.