Rare-earth metal allyl and hydrido complexes supported by an (NNNN)-type macrocyclic ligand: synthesis, structure, and reactivity toward biomass-derived furanics

The preparation and characterization of a series of neutral rare‐earth metal complexes [Ln(Me₃TACD)(η³‐C₃H₅)₂] (Ln=Y, La, Ce, Pr, Nd, Sm) supported by the 1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane anion (Me₃TACD^?) are reported. Upon treatment of the neutral allyl complexes [Ln(Me₃TACD)(η³‐C₃H₅)₂] with Brønsted acids, monocationic allyl complexes [Ln(Me₃TACD)(η³‐C₃H₅)(thf)₂][B(C₆X₅)₄] (Ln=La, Ce, Nd, X=H, F) were isolated and characterized. Hydrogenolysis gave the hydride complexes [Ln(Me₃TACD)H₂]_n (Ln=Y, n=3; La, n=4; Sm). X‐ray crystallography showed the lanthanum hydride to be tetranuclear. Reactivity studies of [Ln(Me₃TACD)R₂]_n (R=η³‐C₃H₅, n=0; R=H, n=3,4) towards furan derivatives includes hydrosilylation and deoxygenation under ring‐opening conditions.     

Determination of carbon isotope ratios in amino acids,proteins, and oligosaccharides by inductively coupled plasma-mass spectrometry

Carbon isotope ratios ((12)C/(13)C) are measured for aqueous solutions of tryptophan, myoglobin, and beta-cyclodextrin using C(+) ions from an inductively coupled plasma (ICP) and a prototype twin quadrupole mass spectrometer (MS). (13)C/(12)C ratios can be determined with a relative standard deviation (RSD) of approximately 1%. This precision is close to the limiting value predicted by counting statistics (1.16%). Spectral interference on (13)C(+), presumably from (12)C(1)H(+), comes from the incomplete dissociation of myoglobin and/or beta-cyclodextrin, but not tryptophan. Decreasing the aerosol gas flow rate slightly from that which yields maximum signal eliminates this (12)C(1)H(+) interference. The count rate of the minor isotope ((13)C(+)) can be artificially enhanced by increasing the voltage of the (13)C(+) detector, and/or by shifting the ion beam splitter offset from the central axis. Instrumental modifications to the MS that improve the sensitivity are also described.     

Mannose‐6‐Phosphate Receptor: A Target for Theranostics of Prostate Cancer

The development of personalized and non‐invasive cancer therapies based on new targets combined with nanodevices is a major challenge in nanomedicine. In this work, the over‐expression of a membrane lectin, the cation‐independent mannose 6‐phosphate receptor (M6PR), was specifically demonstrated in prostate cancer cell lines and tissues. To efficiently target this lectin a mannose‐6‐phosphate analogue was synthesized in six steps and grafted onto the surface of functionalized mesoporous silica nanoparticles (MSNs). These MSNs were used for in vitro and ex vivo photodynamic therapy to treat prostate cancer cell lines and primary cell cultures prepared from patient biopsies. The results demonstrated the efficiency of M6PR targeting for prostate cancer theranostic.     

A single DNA aptamer functions as a biosensor for ricin

The use of microorganisms or toxins as weapons of death and fear is not a novel concept; however, the modes by which these agents of bioterrorism are deployed are increasingly clever and insidious. One mechanism by which biothreats are readily disseminated is through a nation's food supply. Ricin, a toxin derived from the castor bean plant, displays a strong thermostability and remains active at acidic and alkaline pHs. Therefore, the CDC has assigned ricin as a category B reagent since it may be easily amendable as a deliberate food biocontaminate. Current tools for ricin detection utilize enzymatic activity, immunointeractions and presence of castor bean DNA. Many of these tools are confounded by complex food matrices, display a limited dynamic range of detection and/or lack specificity. Aptamers, short RNA and single stranded DNA sequences, have increased affinity to their selected receptors, experience little cross-reactivity to other homologous compounds and are currently being sought after as biosensors for bacterial contaminants in food. This paper describes the selection and characterization of a single, dominant aptamer, designated as SSRA1, against the B-chain of ricin. SSRA1 displays one folding conformation that is stable across 4-63 °C (ΔG = -5.05). SSRA1 is able to concentrate at least 30 ng mL(-1) of ricin B chain from several liquid food matrices and outcompetes a currently available ELISA kit and ricin aptamer. Furthermore, we show detection of 25 ng mL(-1) of intact ricin A-B complex using SSRA1 combined with surface enhanced Raman scattering technique. Thus, SSRA1 would serve well as pre-analytical tool for processing of ricin from liquid foods to aid current diagnostics as well as a sensor for direct ricin detection.     

Relationship between swelling and the electrohydrodynamic properties of functionalized carboxymethyldextran macromolecules

The electrostatic, hydrodynamic, and swelling properties of a well-defined, functionalized carboxymethyldextran (CMD) polysaccharide are investigated in aqueous NaNO3 solution over a broad ionic strength range. The impact of the polycarboxylate charge and molar mass of the CMD macromolecules on their electrohydrodynamic features is thoroughly examined by combined protolytic titration, dynamic light scattering, and electrokinetic analyses. Electrophoretic mobility data obtained for sufficiently high electrolyte concentrations reveal a typical soft particle behavior. Upon decrease of the ionic strength, mobilities strongly increase in magnitude while significant electrostatic swelling takes place, as reflected in a decrease in the diffusion coefficients. CMD entities undergo conformational transitions from compact random coil at large ionic strengths to swollen coil and possibly a wormlike structure at lower NaNO3 concentrations. The magnitude of the variations in size and mobility with electrolyte concentration strongly depends on the overall charge of the CMD entity as well as on its molar mass. These factors control the stiffness of the constituent polymer chains and thus the degree of macromolecular permeability ("softness"). Using the soft-diffuse interface formalism previously developed for the electrohydrodynamics of charged permeable macromolecules, a quantitative analysis of the electrophoretic mobility data is presented. The measured values of the diffusion coefficient and space charge density Gamma degrees, as evaluated independently from the modeling of potentiometric titration curves, are taken into account in a self-consistent manner. It is found that large CMD entities of low charge densities are the most permeable to flow penetration with a limited heterogeneous electrostatic stiffening of the chains, whereas small CMD entities of larger Gamma degrees significantly expand upon lowering the ionic strength, giving rise to a strong anisotropy for the spatial distribution of polymer chain density.     

Photodissociation dynamics of the HCNN radical

The photodissociation dynamics of the diazomethyl (HCNN) radical have been studied using fast radical beam photofragment translational spectroscopy. A photofragment yield spectrum was obtained for the range of 25,510-40,820 cm(-1), and photodissociation was shown to occur for energies above 25,600 cm(-1). The only product channel observed was the formation of CH and N2. Fragment translational energy and angular distributions were obtained at several energies in the range covered by the photofragment yield spectrum. The fragment translational energy distributions showed at least two distinct features at energies up to 4.59 eV, and were not well fit by phase space theory at any of the excitation energies studied. A revised C-N bond dissociation energy and heat of formation for HCNN, D0(HC-NN)=1.139+/-0.019 eV and DeltafH0(HCNN)=5.010+/-0.023 eV, were determined.     

Stereoconvergent Synthesis of Z-1,3-Disubstituted-1,3-Dienes by Uphill Photocatalysis

A variety of 1-aryl-1,3-dienes were isomerized from E to Z isomers by photocatalysis using Ru(bpy)₃[PF₆]₂ and blue LED light. Enrichment of the Z-isomer is thought to occur by selective triplet energy transfer from the photocatalyst to the stereoisomeric mixture. The 1,3-diene starting materials are easily made by catalytic ene-yne metathesis (EYM). To access 1,3-diene Z-stereoisomers directly, a one pot procedure was developed. Additional 1,3-dienes were investigated for both isomerization and Z-enrichment. The combination of cross EYM with photocatalysis allows for the stereoconvergent synthesis of Z-1,3-dienes.     

Dependency of the Dimethyldihydropyrene Photochromic Properties on the Number of Pyridinium Electron-Withdrawing Groups

Photochromic dimethyldihydropyrenes substituted with electron-withdrawing pyridinium groups have shown an increase of photo-induced ring-opening efficiency and a light sensitivity that is red shifted relative to the unsubstituted compound. However, a recently synthesized tetrapyridinium derivative showed a considerable decrease of the photo-isomerization quantum yield relative to the monopyridinium and bispyridinium derivatives. We provide a rationale for this unexpected photochemical behavior based on the comparative theoretical investigations of the relevant excited states of these systems. In particular, we found that the nature and order of the lowest two excited states depend on the number of pyridinium groups and on the symmetry of the system. While the lowest S₁ excited state is photo-active in the monopyridinium and bispyridinium derivatives, the photo-isomerizing state is S₂ in the reference unsubstituted compound and both S₁ and S₂ lead to isomerization in the tetrapyridinium derivative, albeit with a low efficiency. In the latter derivative, the photo-isomerization is hindered by the particular S₁/S₂ conical intersection topology.