The Inhibition Effect of Photo-Cross-Linking between Probes in Photo-Induced Double Duplex Invasion DNA

Double duplex invasion (DDI) DNA is a useful antigene method that inhibits expression of genomic DNA. We succeeded in performing photoinduced-DDI (pDDI) using ultrafast photo-cross-linking. 5-Cyanouracil (^CNU) has been used in pDDI to inhibit photo-cross-linking between probes, but its importance has not been clarified. Therefore, in this study, we evaluated the effect of spacer (S) and d-spacer (dS) that exhibit photo-cross-linking ability similar to that of ^CNU. ^CNU exhibited the highest pDDI efficiency, and S, dS, and T were not very different. The photo-cross-linking inhibitory effect was better with S and dS than with thymidine (T). Conversely, the thermal stability was significantly lower with S and dS than with T. The results suggest that the pDDI efficiency is determined by the balance between the photo-cross-linking inhibitory effect and the thermal stability, which is the introduction efficiency for double-stranded DNA. Therefore, ^CNU, which has a photo-cross-linking inhibitory effect and a high T_m value, showed the highest inhibitory efficiency.     

Conventionally facile fabrication of mechanically robust waterborne polyurethane with self-healing and photoluminescence

It is of much importance to synthesize waterborne polyurethane (WPUs) that simultaneously broaden the fields of applications and functions in a green strategy. In this paper, a novel class of WPUs were facilely prepared through the copolymerization between polytetrahydrofuran ether diol (PTMG), isophorone diisocyanate, and 2,2-bis(hydroxymethyl)propionic acid, which can achieve multiple functions of self-healing and photoluminescence after incorporating carbon quantum dots (CQs) into the WPUs. The prepared WPUs emulsion showed uniform size distribution from 61.97 nm to171.3 nm with different PTMG molecular weights. Especially, the maximum tensile strength and elongation at break of the WPUs can reach up to 69.78 MPa and 1879.99%, showing superior mechanical performance. After fractured surfaces held contact for 12 h at elevated temperature, the self-healing efficiency of the pristine WPUs can reach 21.39% for tensile strength and 24.79% for elongation at break. After adding CQs, the synthesized WPUs can also remain nearly the same tensile strength and elongation at break. Significantly, the self-healing WPUs with CQs can emit a bright orange fluorescence under ultraviolet light, showing outstanding photoluminescence. This kind of designed material takes advantages of simple preparation, no release of organic solvents during use, nontoxicity and harmlessness.     

Upgrading poly(styrene-co-divinylbenzene) beads: Incorporation of organomodified metal-free semiconductor graphitic carbon nitride through suspension photopolymerization to generate photoactive resins

The inclusion of the metal free semiconductor graphitic carbon nitride (g-CN) into polymer systems brings a variety of new options, for instance as a heterogeneous photoredox polymer initiator. In this context, we present here the decoration of the inner surface of poly(styrene-co-divinylbenzene) beads with organomodified g-CN via one pot suspension photopolymerization. The resulting beads are varied by changing reaction parameters, such as, crosslinking ratio, presence of porogens, and mechanical agitation. The photocatalytic activity of so-formed beads was tested by aqueous rhodamine B dye photodegradation experiments. Additionally, dye adsorption/desorption properties were examined in aqueous as well as in organic solvents. Photoinduced surface modification with vinylsulfonic acid and 4-vinyl pyridine is introduced. Overall, metal-free semiconductor g-CN donates photoactivity to polymer networks that can be employed for dye photodegradation and acid–base catalyst transformation through facile photoinduced surface modifications.     

Preparation of the flexible soybean oil-based material via [2 + 2] cycloaddition photo-polymerization

Polymers with high flexibility and high content renewable biomass materials have attracted particular attention. Plant-derived trans-cinnamic acid (CA) was introduced into the structure of epoxidized soybean oil to form trans-cinnamated epoxidized soybean oil (ESOCA). ESOCA with multi-cinnamate groups was cured via [2 + 2] cycloaddition photo-polymerization that with no need of photoinitiator, while acrylated epoxidized soybean oil (ESOAA) was photocured via free radical photopolymerization for comparison. The successful synthesis of ESOCA and ESOAA resin was proved by Fourier transform infrared, proton nuclear magnetic resonance, and gel permeation chromatography results. ESOCA is more environmentally friendly than ESOAA for that trans-CA volatility is much lower than acrylic acid during synthesis process. Notably, UV-cured ESOCA samples had a higher tensile strength at break and a 14.75 times elongation at break of that of UV-cured ESOAA samples, showing that [2 + 2] cycloaddition photo-polymerization is a good strategy to prepare flexible materials. Performances of ESOCA as coating on flexible PET film were also better than those of ESOAA, especially the flexibility, adhesion, and UV shielding performance. This study may open up a new way for design and synthesize flexible high performance polymer from renewable biomass materials.     

Photochemistry and photophysics of poly(organophosphazenes) and related compounds: A review. III. Applicative aspects

In the third part of this review we report some applicative aspects of poly(organophosphazenes) in photochemical fields. In particular, the possible application of phosphazene polymers that contain azobenzene or spiropyran residues as photochromic macromolecules is outlined; the light-induced grafting of organic, carbon-backboned polymers onto polyphosphazene matrices, as a method of modifying both surface and bulk properties of these materials, is highlighted; and the potential application of cyclophosphazenes as photo-stabilizers for commercial organic polymers or as photoinitiators for radical polymerization of vinyl monomers is described.Parts I and II in this series appeared in this journal, Volume 4, Numbers 1 and 2, 1994, respectively.     

Stability of Polymer:PCBM Thin Films under Competitive Illumination and Thermal Stress

The combined effects of illumination and thermal annealing on the morphological stability and photodimerization in polymer/fullerene thin films are examined. While illumination is known to cause fullerene dimerization and thermal stress their dedimerization, the operation of solar cells involves exposure to both. The competitive outcome of these factors with blends of phenyl‐C61‐butyric acid methyl ester (PCBM) and polystyrene (PS), supported on PEDOT:PSS is quantified. UV–vis spectroscopy is employed to quantify dimerization, time‐resolved neutron reflectivity to resolve the vertical composition stratification, and atomic force microscopy for demixing and coarsening in thin films. At the conventional thermal stress test temperature of 85 °C (and even up to the PS glass transition), photodimerization dominates, resulting in relative morphological stability. Prior illumination is found to result in improved stability upon high temperature annealing, compatible with the need for dedimerization to occur prior to structural relaxation. Modeling of the PCBM surface segregation data suggests that only PCBM monomers are able to diffuse and that illumination provides an effective means to control dimer population, and thus immobile fullerene fraction, in the timescales probed. The results provide a framework for understanding of the stability of organic solar cells under operating conditions.     

Light‐Driven Electrohydrodynamic Instabilities in Liquid Crystals

The induction of electrohydrodynamic instabilities in nematic liquid crystals through light illumination are reported. For this purpose, a photochromic spiropyran is added to the liquid crystal mixture. When an electrical field is applied in the absence of UV light, the homeotropic liquid crystal reorients perpendicular to the electrical field driven by its negative dielectric anisotropy. Upon exposure to UV light, the nonionic spiropyran isomerizes to the zwitterionic merocyanine form inducing electrohydrodynamic instabilities which turns the cell from transparent into highly scattering. The reverse isomerization to closed‐ring spiropyran form occurs thermally or under visible light, which stops the electrohydrodynamic instabilities and the cell becomes transparent again. It is demonstrated that the photoionic electrohydrodynamic instabilities can be used for light regulation. Local exposure, either to drive the electrohydrodynamics or to remove them enables the formation of colored images.     

Heterogeneous production of Cl2 from particulate chloride: Effects of composition and relative humidity

Reactions initiated by chlorine atoms can enhance the formation of ozone (O₃) and secondary organic aerosol (SOA) in the troposphere. Environmental chamber experiments were conducted to quantify heterogeneous Cl₂ production from NH₄Cl and NaCl particles exposed to O₃ and hydroxyl radicals (?OH). Observations are inconsistent with models of Cl₂ production resulting solely from surface‐mediated reactions of ?OH and suggest that O₃ plays a significant role. The production of Cl₂ increased with relative humidity and decreased in the presence of SOA or nitric oxides (NO_x). Heterogeneous reactive uptake coefficients for the production of Cl₂ from O₃ on pure NH₄Cl ( ) averaged 1.4 ± 1.0 × 10^?3. Cl₂ production was six times more efficient on NH₄Cl aerosol than on NaCl aerosol. Model calculations under atmospheric conditions suggest this heterogeneous Cl₂ production could increase peak daily O₃ concentrations by over 10%. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3151–3158, 2018     

Residues at a Single Site Differentiate Animal Cryptochromes from Cyclobutane Pyrimidine Dimer Photolyases by Affecting the Proteins' Preferences for Reduced FAD

Cryptochromes (CRYs) and photolyases belong to the cryptochrome/photolyase family (CPF). Reduced FAD is essential for photolyases to photorepair UV‐induced cyclobutane pyrimidine dimers (CPDs) or 6–4 photoproducts in DNA. In Drosophila CRY (dCRY, a type I animal CRY), FAD is converted to the anionic radical but not to the reduced state upon illumination, which might induce a conformational change in the protein to relay the light signal downstream. To explore the foundation of these differences, multiple sequence alignment of 650 CPF protein sequences was performed. We identified a site facing FAD (Ala377 in Escherichia coli CPD photolyase and Val415 in dCRY), hereafter referred to as “site 377”, that was distinctly conserved across these sequences: CPD photolyases often had Ala, Ser, or Asn at this site, whereas animal CRYs had Ile, Leu, or Val. The binding affinity for reduced FAD, but not the photorepair activity of E. coli photolyase, was dramatically impaired when replacing Ala377 with any of the three CRY residues. Conversely, in V415S and V415N mutants of dCRY, FAD was photoreduced to its fully reduced state after prolonged illumination, and light‐dependent conformational changes of these mutants were severely inhibited. We speculate that the residues at site 377 play a key role in the different preferences of CPF proteins for reduced FAD, which differentiate animal CRYs from CPD photolyases.