Protein Delivery System Containing a Nickel‐Immobilized Polymer for Multimerization of Affinity‐Purified His‐Tagged Proteins Enhances Cytosolic Transfer

Recombinant proteins with cytosolic or nuclear activities are emerging as tools for interfering with cellular functions. Because such tools rely on vehicles for crossing the plasma membrane we developed a protein delivery system consisting in the assembly of pyridylthiourea‐grafted polyethylenimine (πPEI) with affinity‐purified His‐tagged proteins pre‐organized onto a nickel‐immobilized polymeric guide. The guide was prepared by functionalization of an ornithine polymer with nitrilotriacetic acid groups and shown to bind several His‐tagged proteins. Superstructures were visualized by electron and atomic force microscopy using 2 nm His‐tagged gold nanoparticles as probes. The whole system efficiently carried the green fluorescent protein, single‐chain antibodies or caspase 3, into the cytosol of living cells. Transduction of the protease caspase 3 induced apoptosis in two cancer cell lines, demonstrating that this new protein delivery method could be used to interfere with cellular functions.     

Template directed synthesis of antibody Fc conjugates with concomitant ligand release

Antibodies are an attractive therapeutic modality for cancer treatment as they allow the increase of the treatment response rate and avoid the severe side effects of chemotherapy. Notwithstanding the strong benefit of antibodies, the efficacy of anti-cancer antibodies can dramatically vary among patients and ultimately result in no response to the treatment. Here, we have developed a novel means to regioselectively label the Fc domain of any therapeutic antibody with a radionuclide chelator in a single step chemistry, with the aim to study by SPECT/CT imaging if the radiolabeled antibody is capable of targeting cancer cells in vivo. A Fc-III peptide was used as bait to bring a carbonate electrophilic site linked to a metal chelator and to a carboxyphenyl leaving group in close proximity with an antibody Fc nucleophile amino acid (K317), thereby triggering the covalent linkage of the chelator to the antibody lysine, with the concomitant release of the carboxyphenyl Fc-III ligand. Using CHX-A′′-DTPA, we radiolabeled trastuzumab with indium-111 and showed in biodistribution and imaging experiments that the antibody accumulated successfully in the SK-OV-3 xenograft tumour implanted in mice. We found that our methodology leads to homogeneous conjugation of CHX-A′′-DTPA to the antibody, and confirmed that the Fc domain can be selectively labeled at K317, with a minor level of unspecific labeling on the Fab domain. The present method can be developed as a clinical diagnostic tool to predict the success of the therapy. Furthermore, our Fc-III one step chemistry concept paves the way to a broad array of other applications in antibody bioengineering.

A method is reported to attach a radionuclide chelator in a single step chemistry to the Fc domain of any therapeutic antibody.     

Wrapping an Organic Reducing Reagent in a Cationic Boron Complex and Its Use in the Synthesis of Polyhalide Monoanionic Networks

The reaction between BF₃ ? OEt₂ and one of two guanidines, 1,8‐bis(tetramethylguanidinyl)naphthalene (btmgn) and 1,2,4,5‐tetrakis(tetramethylguanidinyl)naphthalene (ttmgn), yields the salts [(btmgn)(BF₂)]BF₄ and [(ttmgn)(BF₂)₂](BF₄)₂. NMR spectroscopic data show that the boron atoms in the cation and anion exchange in the case of [(ttmgn)(BF₂)₂](BF₄)₂, but not in the case of [(btmgn)(BF₂)]BF₄. The rate constant for this exchange was estimated to be 4 s^?1 at 80 °C for solutions in CH₃CN. These salts were subsequently used for the reduction of dihalides Br₂ or I₂ to give polyhalide salts. We report the synthesis and first complete characterization (including structural analysis) of salts that contain pentabromide monoanions. In these salts, the Br₅^? anions interact to give dimeric units or polymeric chains. Our results are compared to previous quantum chemical calculations on the gas‐phase structure of the Br₅^? anion. The possible pathways that lead to the polyhalides are evaluated. In the case of [(ttmgn)(BF₂)₂](BF₄)₂, reduction is accompanied by ttmgn oxidation, whereas in the case of [(btmgn)(BF₂)]BF₄ reduction is initiated by aromatic substitution.     

A universal nucleoside with strong two-band switchable fluorescence and sensitivity to the environment for investigating DNA interactions

With the aim of developing a new tool to investigate DNA interactions, a nucleoside analogue incorporating a 3-hydroxychromone (3HC) fluorophore as a nucleobase mimic was synthesized and incorporated into oligonucleotide chains. In comparison with existing fluorescent nucleoside analogues, this dye features exceptional environmental sensitivity switching between two well-resolved fluorescence bands. In labeled DNA, this nucleoside analogue does not alter the duplex conformation and exhibits a high fluorescence quantum yield. This probe is up to 50-fold brighter than 2-aminopurine, the fluorescent nucleoside standard. Moreover, the dual emission is highly sensitive to the polarity of the environment; thus, a strong shielding effect of the flanking bases from water was observed. With this nucleoside, the effect of a viral chaperone protein on DNA base stacking was site-selectively monitored.     

Hydrogenation of CO2‐Derived Carbonates and Polycarbonates to Methanol and Diols by Metal–Ligand Cooperative Manganese Catalysis

The first base‐metal‐catalysed hydrogenation of CO₂‐derived carbonates to alcohols is presented. The reaction proceeds under mild conditions in the presence of a well‐defined manganese complex with a loading as low as 0.25 mol %. The non‐precious‐metal homogenous catalytic system provides an indirect route for the conversion of CO₂ into methanol with the co‐production of value‐added (vicinal) diols in yields of up to 99 %. Experimental and computational studies indicate a metal–ligand cooperative catalysis mechanism.     

Large-scale protein/antibody patterning with limiting unspecific adsorption

A simple synthetic route based on nanosphere lithography has been developed in order to design a large-scale nanoarray for specific control of protein anchoring. This technique based on two-dimensional (2D) colloidal crystals composed of polystyrene spheres allows the easy and inexpensive fabrication of large arrays (up to several centimeters) by reducing the cost. A silicon wafer coated with a thin adhesion layer of chromium (15 nm) and a layer of gold (50 nm) is used as a substrate. PS spheres are deposited on the gold surface using the floating-transferring technique. The PS spheres were then functionalized with PEG-biotin and the defects by self-assembly monolayer (SAM) PEG to prevent unspecific adsorption. Using epifluorescence microscopy, we show that after immersion of sample on target protein (avidin and anti-avidin) solution, the latter are specifically located on polystyrene spheres. Thus, these results are meaningful for exploration of devices based on a large-scale nanoarray of PS spheres and can be used for detection of target proteins or simply to pattern a surface with specific proteins.     

The Rb7Bi3−3xSb3xCl16 Family: A Fully Inorganic Solid Solution with Room‐Temperature Luminescent Members

Low‐dimensional ns²‐metal halide compounds have received immense attention for applications in solid‐state lighting, optical thermometry and thermography, and scintillation. However, these are based primarily on the combination of organic cations with toxic Pb²⁺ or unstable Sn²⁺, and a stable inorganic luminescent material has yet to be found. Here, the zero‐dimensional Rb₇Sb₃Cl₁₆ phase, comprised of isolated [SbCl₆]^3? octahedra and edge‐sharing [Sb₂Cl₁₀]^4? dimers, shows room‐temperature photoluminescence (RT PL) centered at 560 nm with a quantum yield of 3.8±0.2 % at 296 K (99.4 % at 77 K). The temperature‐dependent PL lifetime rivals that of previous low‐dimensional materials with a specific temperature sensitivity above 0.06 K^?1 at RT, making it an excellent thermometric material. Utilizing both DFT and chemical substitution with Bi³⁺ in the Rb₇Bi_3?3xSb_3xCl₁₆ (x≤1) family, we present the edge‐shared [Sb₂Cl₁₀]^4? dimer as a design principle for Sb‐based luminescent materials.     

Electron photoemission in plasmonic nanoparticle arrays: analysis of collective resonances and embedding effects

We theoretically study the characteristics of photoelectron emission in plasmonic nanoparticle arrays. Nanoparticles are partially embedded in a semiconductor, forming Schottky barriers at metal/semiconductor interfaces through which photoelectrons can tunnel from the nanoparticle into the semiconductor; photodetection in the infrared range, where photon energies are below the semiconductor band gap (insufficient for band-to-band absorption in semiconductor), is therefore possible. The nanoparticles are arranged in a sparse rectangular lattice so that the wavelength of the lattice-induced Rayleigh anomalies can overlap the wavelength of the localized surface plasmon resonance of the individual particles, bringing about collective effects from the nanoparticle array. Using full-wave numerical simulations, we analyze the effects of lattice constant, embedding depth, and refractive index step between the semiconductor layer and an adjacent transparent conductive oxide layer. We show that the presence of refractive index mismatch between media surrounding the nanoparticles disrupts the formation of a narrow absorption peak associated with the Rayleigh anomaly, so the role of collective lattice effects in the formation of plasmonic resonance is diminished. We also show that 5–20 times increase of photoemission can be achieved on embedding of nanoparticles without taking into account dynamics of ballistic electrons. The results obtained can be used to increase efficiency of plasmon-based photodetectors and photovoltaic devices. The results may provide clues to designing an experiment where the contributions of surface and volume photoelectric effects to the overall photocurrent would be defined.