Photoinduced electron transfer between cytochrome c and a novel 1,4,5,8-naphthalenetetracarboxylic diimide with amphiphilic character

N-dodecyl-N'-(2-phosphonoethyl)-1,4,5,8-naphthalenetetracarboxylic diimide (DNDI) is a novel naphthalenic diimide with amphiphilic character. DNDI was synthesized through the sequential reaction of 1,4,5,8-naphthalenetetracarboxylic dianhydride, first with dodecylamine and then with 2-aminoethylphosphonic acid. Fluorescence measurements showed that DNDI forms excimers in water at sufficiently high concentrations. The fluorescence quantum yield of DNDI in diluted solutions is sensitive to the polarity of the microenvironment, decreasing as going from water to less polar solvents. This property allowed to monitor the incorporation of DNDI into cetyl trimethyl ammonium bromide (CTAB) micelles, with a binding constant of 1.2x10(4) M-1. UV irradiation (365 nm) of solutions containing DNDI and the redox protein cytochrome c (cyt c) resulted in the reduction of the heme iron from the Fe(III) to the Fe(II) state, a reaction that was inhibited by the incorporation of DNDI into CTAB micelles. DNDI formed host-guest complexes with alpha-cyclodextrin (alpha-CD) through the inclusion of the dodecyl group, resulting in an increased aqueous solubility of the compound.     

On the relationship between the structures of Cu(II) complexes and their chemical transformations

The experimental activation energies (E ^*) of dehydration of Cu(NH₃)₄(H₂O)SO₄, Cu(en)₂(H₂O)X₂ (X=Cl^?, Br^?), Cu(en)(H₂O)₂SO₄, Cu(py)₂(H₂O)₂SO₄, CuCl₂ · 2H₂O and M ₂ ^I CuCl₄ · 2H₂O (M ^I =NH₄, K, Rb) were obtained from their non-isothermal thermogravimetric curves using the Coats-Redfern method. TheseE ^* values were compared with known data on the structures of the Cu(II) coordination polyhedra in the above complexes. No dependence of theE ^* values was found on either the central atom — released ligand bond length, or the number and lengths of the hydrogen bonds formed by the released water molecules. However, it was found that it is justified to seek some relationship between theE ^* values and the anisotropic temperature factors of the donor atoms of the ligands split off.     

Frequency‐Driven Self‐Organized Helical Superstructures Loaded with Mesogen‐Grafted Silica Nanoparticles

Adding colloidal nanoparticles into liquid‐crystal media has become a promising pathway either to enhance or to introduce novel properties for improved device performance. Here we designed and synthesized new colloidal hybrid silica nanoparticles passivated with a mesogenic monolayer on the surface to facilitate their organo‐solubility and compatibility in a liquid‐crystal host. The resulting nanoparticles were identified by ¹H NMR spectroscopy, TEM, TGA, and UV/Vis techniques, and the hybrid nanoparticles were doped into a dual‐frequency cholesteric liquid‐crystal host to appraise both their compatibility with the host and the effect of the doping concentration on their electro‐optical properties. Interestingly, the silica‐nanoparticle‐doped liquid‐crystalline nanocomposites were found to be able to dynamically self‐organize into a helical configuration and exhibit multi‐stability, that is, homeotropic (transparent), focal conic (opaque), and planar states (partially transparent), depending on the frequency applied at sustained low voltage. Significantly, a higher contrast ratio between the transparent state and scattering state was accomplished in the nanoparticle‐embedded liquid‐crystal systems.     

Interpenetrated nano-capsule networks based on the alkali metal assisted assembly of p-carboxylatocalix[4]arene-O-methyl ether

Reaction of p-carboxylatocalix[4]arene-O-methyl ether with either rubidium or caesium hydroxide results in the formation of interpenetrated nano-capsule networks with the calixarene in the 1,3-alternate conformation.     

Thermal dependency of RAG1 self-association properties

Background  

Functional immunoglobulin and T cell receptor genes are produced in developing lymphocytes by V(D)J recombination. The initial site-specific DNA cleavage steps in this process are catalyzed by the V(D)J recombinase, consisting of RAG1 and RAG2, which is directed to appropriate DNA cleavage sites by recognition of the conserved recombination signal sequence (RSS). RAG1 contains both the active site and the RSS binding domains, although RAG2 is also required for DNA cleavage activity. An understanding of the physicochemical properties of the RAG proteins, their association, and their interaction with the RSS is not yet well developed.     

Accessible and Cost-Effective Method of PDMS Microdevices Fabrication Using a Reusable Photopolymer Mold

This work describes a novel and cost-effective method of polydimethylsiloxane (PDMS) microchips fabrication by using a printing plate photopolymer called Flexcel as a master mold (Fmold). This method has demonstrated the ability to generate multiple devices from a single master, reaching a minimum channel size of 25 μm, structures height ranging from 53 to 1500 μm and achieving dimensions of 1270 × 2062 mm², which are larger than those obtained by the known techniques to date. Scanning electron microscopy, atomic force microscopy, and profilometry techniques have been employed to characterize the Fmold and PDMS replicas. The results showed high replication fidelity of Fmold to the PDMS replica. Furthermore, it was proved the reusability of the Fmold. In our study, up to 50 PDMS replicas have been fabricated without apparent degradation of the mold. The feasibility of the resulting PDMS replica was effectively demonstrated using a microfluidic device for enhanced oil recovery analysis. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1433–1442     

A molecularly imprinted polymer as the sorptive phase immobilized in a rotating disk extraction device for the determination of diclofenac and mefenamic acid in wastewater

The microextraction of diclofenac and mefenamic acid from water samples was performed by using rotating disk sorptive extraction (RDSE) with molecularly imprinted polymer (MIP) as the sorptive phase. The MIP was synthesized from the monomer 1-vinylimidazol (VI) together with the cross-linker divinylbenzene (DVB) using diphenylamine as the template molecule. Scanning electron microscopy (SEM) analyses of the MIP revealed clusters of spherical particles having a narrow size distribution, with diameters of approximately 1 μm.     

Quick and Easy Modification of Glassy Carbon Electrodes with Ionic Liquid and Tetraruthenated Porphyrins for the Electrochemical Determination of Atrazine in Water

Atrazine is a pesticide used to control broadleaf weeds, however its wide distribution and its high persistence in the soil and in surface waters has resulted in a public and environmental health problem. Present results shows the design, construction and characterization of glassy carbon electrodes modified with tetrarutenated metalloporphyrin (M=Ni (II) and Zn (II)) and 1‐butyl‐3‐methylimidazolium bis (trifluoromethylsulfonyl) imide, BMIMNTF₂. The modification was reproducible and sensitive for the electrochemical detection of atrazine in neutral media. The detection limit was 230 nM when using GC/BMIMNTF₂/ZnTRP and 540 nM with GC/BMIMNTF₂/NiTRP, meaning that his methodology can be a feasible and inexpensive way to detect atrazine in trace levels.     

Syntheses of aza-analogous iso-ergoline scaffolds using carbene mediated C-H insertion

A novel direct, flexible, and robust approach to the iso-ergoline tetracyclic system in which a five or six-membered ring is established by intramolecular carbene C-H insertion is reported. The protocol involves a two step conversion of an aromatic aldehyde to the corresponding hydrazone and without purification further conversion to the diazo-compound followed by thermal carbene formation and C-H insertion α to a nitrogen.     

A novel mononuclear square-planar copper(II) complex (Pip-H+)2[CuL4]2? with 2-cyano-3-(2,5-dimethoxyphenyl)acrylic acid as ligand: synthesis, crystal structures, spectral and thermal studies

Abstract  

2-Cyano-3-(2,5-dimethoxyphenyl)acrylic acid and its novel mononuclear square-planar copper(II) complex dipiperidinium tetrakis[2-cyano-3-(2,5-dimethoxyphenyl)acrylic acid]copper(II) ((Pip-H⁺)₂[CuL₄]²⁻) were synthesized and characterized by elemental analyses, FT–IR, UV–Vis spectroscopy, and thermogravimetric analysis. Moreover, the ligand was characterized by ¹H and ¹³C NMR spectroscopy. The structures of the ligand and its copper(II) complex were confirmed by single-crystal X-ray crystallography. Whereas the ligand crystallizes in the triclinic space group Pī with unit cell parameters a = 4.6911(2) ?, b = 9.0181(4) ?, c = 13.7084(6) ?, α = 74.946(4)°, β = 87.152(4)°, γ = 89.220(4)°, V = 559.34(4) ?³, and Z = 2, the complex crystallizes in the orthorhombic space group Pccn with unit cell parameters a = 27.5486(5) ?, b = 12.9484(2) ?, c = 15.8822(3) ?, V = 5,665.34(17) ?³, and Z = 4.