A novel and convenient preparation of antibacterial polyacrylonitrile nanofibers via post-modification using nitrile click chemistry and electrospinning

An efficient, novel and convenient method for the synthesis of modified polyacrylonitrile (PAN) with antibacterial property is reported. The modification of PAN was prepared by a nitrile click chemistry reaction with sodium azide (NaN₃) and silver nitrate (AgNO₃) as catalyst to yield antibacterial polymeric materials with 5-vinyltetrazole units. The results showed that 5-vinyltetrazole units had coordinated with silver ion (Ag⁺). Through the electrostatic spinning technology, the post-modification PAN nanofibers (PAN–Ag⁺ nanofibers) were prepared and the fibers were tested for their antimicrobial properties by the bacterial infection experiment. Afterwards, the antibacterial and stable performance of different proportions of silver ions in PAN nanofibers has been compared. The PAN–Ag⁺ nanofibers are characterized for mechanical and thermomechanical properties, structural analysis, appearance characteristics, as well as the antibacterial properties. And the nanofibers exhibit marvelous chemical stability according to the thermogravimetric analysis. When at 800 °C, the PAN decomposed about 60%, while the decomposition of the PAN–Ag⁺s was 40%. Based on the bacterial infection experiment, PAN–Ag⁺ nanofibers’ antibacterial properties were stronger with the increase of silver ions, such as the number of bacteria clone was smaller and the bacteriostatic ring was larger. Hence, with combination of silver ions, the final polymers show strong antimicrobial properties.     

Synthesis,characterization, DNA binding,topoisomerase I inhibition,and antiproliferation activities of (di-<Emphasis Type="Italic">tert</Emphasis>-butylbipyridine) platinum(II) complexes

Two mononuclear Pt(II) complexes, Pt(dbbpy)Cl₂ (1) and [Pt(dbbpy)₂](PF₆)₂ (2) (dbbpy?=?4,4′-ditertbutyl-2,2′-biyridine) were synthesized and characterized by single-crystal X-ray diffraction analysis, elemental analysis, ¹H NMR, and ESI–MS. Their binding affinities for both double-stranded (DS) calf thymus DNA (ct-DNA) and G-quadruplex DNA (HT21 and BCL-2) were investigated. In addition to structural differences, complex 1 displayed higher binding affinity for DS ct-DNA, whereas positively charged complex 2 was selective for binding to G-quadruplex DNA over DS DNA. The time-dependent cleavage of supercoiled circular plasmid pBR322 DNA by 1 was observed using agarose gel electrophoresis, whereas complex 2 hardly cleaved DS DNA. Stabilization of G-quadruplex HT21 DNA by both complexes was assessed by PCR stop assays. Both complexes exhibited moderate activities for inhibition of topoisomerase I as well as modest antiproliferation activities toward cancer cells in CKK-8 assays.     

Geminal Dicationic Ionothermal Synthesis of One Three-Dimensional Luminescent Strontium(II) Coordination Polymer Based on 1,4-Naphthalenedicarboxylate Acid

One three-dimensional Sr(II) coordination polymer [C₆(MIm)₂][Sr₃(1,4-NDC)₄] (I) (C₆(MIm)₂ = 1,3-bis(3-methylimidazolium-1-yl)hexyl, 1,4-H₂NDC = 1,4-naphthalenedicarboxylate acid) has been synthesized using an ionothermal method and structurally characterized by IR spectroscopy, UV-Vis spectroscopy, XRPD, and X-ray single-crystal structure analysis (СIF file CCDC 1033958). Two types of strontium centers are bridged by two coordination modes of 1,4-H₂NDC ligands to form a Sr(II) chain. Each Sr(II) chain is crossconnected to four other chains to generate a 3D coordination polymer, in which C₆(MIm) ₂ ²⁺ cations as charge balancing species are filled in the channels of the anionic framework. The polymeric solid of I exhibits strong luminescent emission at room temperature.     

CuX2-mediated halocyclization of 1,1-difluoro-2,3-allenylphosphonic acid monoesters –synthesis of novel cyclic phosphate mimics

Novel six-membered cyclic phosphate mimics (5-halo-3,3-difluoro-3,6-dihydro-2H-1,2-oxaphosphinine 2-oxides) were synthesized via CuX₂ (X?=?Br, Cl)-mediated halocyclization of 1,1-difluoro-2,3-allenylphosphonic acid monoesters in moderate to good yields with high regio-selectivity. This reaction represents the first example of transition metal-mediated intramolecular cyclization of a P-OH moiety to β-allenylphosphonates with a carbon-carbon double bond.     

Effect of π–π interaction between carbon nanotubes and phenyl groups on the thermal stability of silicone rubber

Journal of Thermal Analysis and Calorimetry - To investigate the effect and mechanism of π–π interaction between carbon nanotubes (CNTs) and phenyl groups on the thermal stability...     

High-efficiency nonvolatile holographic storage with two-step recording in praseodymium-doped lithium niobate by use of continuous-wave lasers

We have observed efficient two-photon, two-step recording in a praseodymium-doped lithium niobate crystal by use of cw lasers. Single-photon erasure during the readout at near-infrared wavelengths was found to be negligible. Nonvolatile holographic image storage was demonstrated. This progress is an important step in the realization of an economically feasible nonvolatile read-write holographic recording system based on low-cost semiconductor diode lasers.     

Site-specific binding of chelerythrine and sanguinarine to single pyrimidine bulges in hairpin DNA

Spectrofluorometric titration, electrospray ionization time-of-flight mass spectrometric and UV melting methods were employed to study the binding of chelerythrine and sanguinarine to bulged DNA. The results showed that both alkaloids bind specifically to single pyrimidine (C, T) bulge sites. The ability of sanguinarine to bind to both regular and bulged hairpins was found to be stronger than that of chelerythrine, but the binding selectivity of chelerythrine toward single-base bulges was much larger than that of sanguinarine. Figure Association constants for chelerythrine and sanguinarine toward regular and single-base bulged hairpins obtained from fluorometric analysis     

Isolation of an [SNS]Pd(II) pincer with a water ladder and its Suzuki coupling activity in water

A water-compatible Pd(ii) pincer with a hybrid [SNS]-donor set, [L(1)PdCl]Cl.2H(2)O [L(1) = bis-(2-(i-butylsulfanyl)-ethyl)-amine] has been isolated and crystallographically characterized; its solid lattice at 223 K contains a ladder-like water polymer of tetramers and extensive H-bonding exists among the cation, anion and water cluster, and this water-soluble complex is active in Suzuki-Miyaura coupling of phenylboronic acid and selected aryl bromides in water at 75 degrees C.     

Theoretical studies on the electronic structures and spectroscopic properties for a series of Osmium(II)-2,2′,6′,2′′-terpyridine complexes

A series of Osmium(II) complexes [Os (trpy-R)₂]²⁺(trpy=2,2′,6′,2′′-terpyridine and R=H (1), OH (2), and C₆H₅(3)) have been investigated by the density functional (DF) and ab initio calculations. The structures of 1–3 in the ground and excited states were fully optimized at the B3LYP and CIS level, respectively, and their absorption and emission spectra in the acetonitrile solution were obtained using the TD-DFT (B3LYP) method associated with the PCM model. The calculations indicated that, for 1–3, the variation of the substituents on the terpyridine ligand only slightly changes their geometrical structures in the ground and excited states but leads to a sizable difference in the electronic structures. The results show that the low-lying MLCT/ILCT transitions (at 446 (1), 465 (2), and 499 nm (3)) are red-shifted according to the electron-donating ability of substituents on the terpyridine ligand, but blue-shift trend of the high-lying ILCT transitions (at 301 (1), 297 (2), and 272 nm (3)). It also reveals that the lowest energy emissions of 1–3 at 649 nm, 656 nm, and 676 nm have the character of mixing ³[π*(trpy) → d(Os)] and ³ ππ* (³MLCT/³ILCT) transitions localized on the terpyridine ligand, which are identical to the transition properties of the lowest-energy absorptions.