Cross‐Platform DNA Encoding for Single‐Cell Imaging of Gene Expression

Integration of imaging data across different molecular target types can provide in‐depth insight into cell physiology and pathology, but remains challenging owing to poor compatibility between target‐type‐specific labeling methods. We show that cross‐platform imaging analysis can be readily achieved through DNA encoding of molecular targets, which translates the molecular identity of various target types into a uniform in situ array of ssDNA tags for subsequent labeling with complementary imaging probes. The concept was demonstrated through multiplexed imaging of mRNAs and their corresponding proteins with multicolor quantum dots. The results reveal heterogeneity of cell transfection with siRNA and outline disparity in RNA interference (RNAi) kinetics at the level of both the mRNA and the encoded protein.     

Photo‐Fenton and Riboflavin‐photosensitized Processes of the Isoxaflutole Herbicide

The proherbicide Isoxaflutole (IXF) hydrolyzes spontaneously to diketonitrile (DKN) a phytotoxic compound with herbicidal activity. In this work, the sensitized degradation of IXF using Riboflavin (Rf), a typical environmentally friendly sensitizer, Fenton and photo‐Fenton processes has been studied. The results indicate that only the photo‐Fenton process produces a significant degradation of the IXF. Photolysis experiments of IXF sensitized by Riboflavin is not a meaningful process, IXF quenches the Rf excited triplet (³Rf*) state with a quenching rate constant of 1.5 · 10⁷ m ^?1 s^?1 and no reaction is observed with the species O₂(¹Δ_g) or ${\mathrm{O}}_2^{·?}$ generated from ³Rf*. The Fenton reaction produces no changes in the IXF concentration. While the photo‐Fenton process of the IXF, under typical conditions, it produces a degradation of 99% and a mineralization to CO₂ and H₂O of 88%. A rate constant value of 1.0 × 10⁹ m ^?1 s^?1 was determined for the reaction between IXF and HO˙. The photo‐Fenton process degradation products were identified by UHPLC‐MS/MS analysis.     

Photo‐Cross‐Linking of Polymethacrylates with Stilbene Chromophores in the Side Chains

Methacrylates (=2‐methylpropenoates) 5 with (E)‐stilbene (=(E)‐1,2‐diphenylethene) building blocks on tethers of variable length were prepared (Scheme 2) and polymerized (i.e., 5 → 6 ; Scheme 3) in the presence of AIBN (=2,2′‐azobis(2‐methylpropanenitrile). 4‐[(E)‐2‐Phenylethenyl]phenyl acetate ( 7 ) as model compound established the cyclodimerization as a single irreversible photoreaction. i.e., ( 7 → 8 – 11 ; Scheme 4) in the absence of oxygen. The solution photolysis of the polymers 6 provided a similar result, whereby [2π+2π] cycloadditions of stilbene units of neighboring tethers predominated. On the contrary, the desired photo‐cross‐linking of chaines occurred in the irradiation of polymer films.     

Iron promotion of V‐HMS mesoporous catalysts for ultra‐deep oxidative desulfurization

Bimetallic Fe‐V‐HMS (HMS, hexagonal mesoporous silica) catalysts with various molar ratios of iron to vanadium were synthesized using a co‐synthesis method, and investigated for oxidative desulfurization of dibenzothiophene (DBT) using tert‐butyl hydroperoxide as an oxidant. The catalysts were characterized using X‐ray diffraction, temperature‐programmed desorption of ammonia, Fourier transform infrared spectroscopy and N₂ physical adsorption–desorption techniques. The Fe‐V‐HMS catalyst with a 2:1 molar ratio of iron to vanadium exhibited the highest total acidity and the highest catalytic activity. DBT was almost completely oxidized to dibenzothiophenesulfone, a species with a higher polarity that could be subsequently adsorbed on the Fe‐V‐HMS, and therefore the Fe‐V‐HMS acts as both a catalyst and an adsorbent simultaneously. The desulfurization rate was 98.1%. A pseudo‐first‐order model was fitted to the experimental data, and the activation energy was found to be 38.79 kJ mol^?1. The encouraging performance of Fe‐V‐HMS offers the prospect of the design of a one‐pot oxidative desulfurization process without needing extraction of sulfones from fuel oil with a chemical solvent.     

Re‐Gradation of Photo‐Oxidized Post‐Consumer Greenhouse Films

Summary: The degradation undergone by the polymers during their use and because of the thermo‐mechanical degradation undergone during the reprocessing operations provokes, among other effects, the decrease of the molecular weight. The change of the molecular architecture is responsible for the deterioration of all the properties. In order to restore the properties of post‐consumer recycled plastics, some rebuilding of the molecular structure is necessary. In this work, photo‐oxidized films for greenhouses were reprocessed in presence of additives able to react with the polyethylene in order to form branching and cross‐linking, improving the properties of these post‐consumer plastic.

Pressure as a function of time in the mini twin‐screw extruder, processing speed 70 rpm.     

Photo‐induced surface transformations of silica nanocomposites

The photo‐induced, physicochemical surface transformations to silica nanoparticle (SiNP) ‐ epoxy composites have been investigated. The silica nanocomposites (SiNCs) were prepared using a two‐part epoxy system with a 10% mass fraction of SiNPs and exposed to varying doses of high intensity, ultraviolet (UV) radiation at wavelengths representative of the solar spectrum at sea level (290 nm to 400 nm) under constant temperature and humidity. Visibly apparent physical modifications to the SiNC surface were imaged with scanning electron microscopy. Surface pitting and cracking became more apparent with increased UV exposure. Elemental and surface chemical characterization of the SiNCs was accomplished through X‐ray energy dispersive spectroscopy and X‐ray photoelectron spectroscopy, while attenuated total reflectance Fourier transform infrared spectroscopy revealed changes to the epoxy's structure. During short UV exposures, there was an increase in the epoxy's overall oxidation, which was accompanied by a slight rise in the silicon and oxygen components and a decrease in overall carbon content. The initial carbon components (e.g. aliphatic, aromatic and alcohol/ether functionalities) decreased and more highly oxidized functional groups increased until sufficiently long exposures at which point the surface composition became nearly constant. At long exposure times, the SiNC's silicon concentration increased to form a surface layer composed of approximately 75% silica (by mass). Published 2012. This article is a U.S. Government work and is in the public domain in the USA.     

Photo‐Organocatalysis of Atom‐Transfer Radical Additions to Alkenes

We have found that an organic molecule as simple as p‐anisaldehyde efficiently catalyzes the intermolecular atom‐transfer radical addition (ATRA) of a variety of haloalkanes onto olefins, one of the fundamental carbon–carbon bond‐forming transformations in organic chemistry. The reaction requires exceptionally mild reaction conditions to proceed, as it occurs at ambient temperature and under illumination by a readily available fluorescent light bulb. Initial investigations support a mechanism whereby the aldehydic catalyst photochemically generates the reactive radical species by sensitization of the organic halides by an energy‐transfer pathway.     

The p53‐Dependent Expression of Frataxin Controls 5‐Aminolevulinic Acid‐Induced Accumulation of Protoporphyrin IX and Photo‐Damage in Cancerous Cells

Mitochondrial frataxin is involved in various functions such as iron homeostasis, iron–sulfur cluster biogenesis, the protection from oxidative stress and apoptosis and acts as a tumor suppressor protein. We now show that the expression of frataxin is stimulated in a p53‐dependent manner and prove that frataxin is a direct p53 target gene by showing that the p53‐responsive element in the promoter of the mouse frataxin gene is bound by p53. The bacterial expression of human frataxin stimulated maturation of human ferrochelatase, which catalyzes the insertion of iron into protoporphyrin at the last step of heme biosynthesis. Overexpression of frataxin in human cancer A431 and HeLa cells lowered 5‐aminolevulinic acid(ALA)‐induced accumulation of protoporphyrin and induced resistance to ALA‐induced photo‐damage, whereas p53 silencing with siRNA in non tumor HEK293T cells down‐regulated the expression of frataxin and increased the accumulation of protoporphyrin. Thus, the decrease of the expression of frataxin unregulated by p53 in tumor cells enhances ALA‐induced photo‐damage, by down‐regulation of mitochondrial functions.     

Photo‐co‐carcinogenesis of Topically Applied Retinyl Palmitate in SKH‐1 Hairless Mice

Cosmetic products that contain retinyl palmitate are popular as antiaging skin treatments; however, recent studies suggest a risk for enhanced skin tumor development with topical retinyl palmitate applications and exposure to solar ultraviolet radiation (UVR). In this study, we investigated the potential of retinyl palmitate to enhance UVR‐induced photo‐co‐carcinogenesis. Groups of 36 male and 36 female SKH‐1 hairless mice were exposed to simulated solar light (SSL) and treated with the control cream or creams containing retinyl palmitate, 5 days per week for 40 weeks. Other groups of mice were exposed to SSL and received no cream treatment or received cream treatments and were exposed to ultraviolet‐A or ultraviolet‐B. Mice were monitored for the development of skin tumors, and the incidences and multiplicities of squamous cell neoplasia were determined by histopathology. In both the absence and presence of SSL, mice administered the control cream developed skin tumors earlier and had higher incidences and multiplicities of skin squamous cell neoplasms than mice that received no cream treatment. Compared to the control cream groups, mice exposed to SSL and administered the retinyl palmitate creams demonstrated earlier onsets of skin tumors and had increased incidences and multiplicities of squamous cell skin neoplasms.     

Aggregation‐Induced Emission and Aggregation‐Promoted Photo‐oxidation in Thiophene‐Substituted Tetraphenylethylene Derivative

Aggregation‐induced emission combined with aggregation‐promoted photo‐oxidation has been reported only in two works quite recently. In fact, this phenomenon is not commonly observed for AIE‐active molecules. In this work, a new tetraphenylethylene derivative (TPE‐4T) with aggregation‐induced emission (AIE) and aggregation‐promoted photo‐oxidation was synthesized and investigated. The pristine TPE‐4T film exhibits strong bluish‐green emission, which turns to quite weak yellow emission after UV irradiation. Interestingly, after solvent treatment, the weakly fluorescent intermediate will become bright‐yellow emitting. Moreover, the morphology of the TPE‐4T film could be regulated by UV irradiation. The wettability of the TPE‐4T microcrystalline surface is drastically changed from hydrophobic to hydrophilic. This work contributes a new member to the aggregation induced photo‐oxidation family and enriches the photo‐oxidation study of tetraphenylethylene derivatives.     

A Photo‐responsive Small‐Molecule Approach for the Opto‐epigenetic Modulation of DNA Methylation

Controlling the functional dynamics of DNA within living cells is essential in biomedical research. Epigenetic modifications such as DNA methylation play a key role in this endeavour. DNA methylation can be controlled by genetic means. Yet there are few chemical tools available for the spatial and temporal modulation of this modification. Herein, we present a small‐molecule approach to modulate DNA methylation with light. The strategy uses a photo‐tuneable version of a clinically used drug (5‐aza‐2′‐deoxycytidine) to alter the catalytic activity of DNA methyltransferases, the enzymes that methylate DNA. After uptake by cells, the photo‐regulated molecule can be light‐controlled to reduce genome‐wide DNA methylation levels in proliferating cells. The chemical tool complements genetic, biochemical, and pharmacological approaches to study the role of DNA methylation in biology and medicine.     

Photo‐/Baso‐Chromisms and the Application of a Dual‐Addressable Molecular Switch

Two typical molecular switches of spiropyran (SP) and benzoxazine (OX) were fused by sharing an indole to achieve a new dual‐addressable molecular switch (SP‐OX‐NO₂). Through proper molecular modification with NO₂, the transformation from merocyanine (MC) to ring‐closed SP or ring‐closed OX can be controlled separately with visible light or base stimuli in solution, respectively, and these processes are verified by UV‐vis and NMR spectroscopy as well as control experiments. The cis‐merocyanine (cis‐MC) form is involved in the basochromic process in solution. DFT calculation suggests that the bidirectional switching property of the fused SP‐OX molecular switch can be controlled separately, when the OX isomer is more stable than the deprotonated SP isomer. Because of the significant color variations in solution, the simple dual‐addressable switch has been further successfully applied to construct a multicolor reversible display on paper.     

Photo‐induced and Rapid Labeling of Tetrazine‐Bearing Proteins via Cyclopropenone‐Caged Bicyclononynes

Inverse electron‐demand Diels–Alder cycloadditions (iEDDAC) between tetrazines and strained alkenes/alkynes have emerged as essential tools for studying and manipulating biomolecules. A light‐triggered version of iEDDAC (photo‐iEDDAC) is presented that confers spatio‐temporal control to bioorthogonal labeling in vitro and in cellulo. A cyclopropenone‐caged dibenzoannulated bicyclo[6.1.0]nonyne probe (photo‐DMBO) was designed that is unreactive towards tetrazines before light‐activation, but engages in iEDDAC after irradiation at 365 nm. Aminoacyl tRNA synthetase/tRNA pairs were discovered for efficient site‐specific incorporation of tetrazine‐containing amino acids into proteins in living cells. In situ light activation of photo‐DMBO conjugates allows labeling of tetrazine‐modified proteins in living E. coli. This allows proteins in living cells to be modified in a spatio‐temporally controlled manner and may be extended to photo‐induced and site‐specific protein labeling in animals.     

Photo‐Tethers for the (Multi‐)Cyclic,Conformational Caging of Long Oligonucleotides

Intramolecular circularization of DNA oligonucleotides was accomplished by incorporation of alkyne‐modified photolabile nucleosides into DNA sequences, followed by a Cu^I‐catalyzed alkyne–azide cycloaddition with bis‐azido linker molecules. We determined a range of ring sizes, in which the caged circular oligonucleotides exhibit superior duplex destabilizing properties. Specific binding of a full‐length 90 nt C10 aptamer recognizing human Burkitt's lymphoma cells was then temporarily inhibited by locking the aptamer in a bicircularized structure. Irradiation restored the native aptamer conformation resulting in efficient cell binding and uptake. The photo‐tether strategy presented here provides a robust and versatile tool for the light‐activation of longer functional oligonucleotides, noteworthy without prior knowledge on the structure and the importance of specific nucleotides within a DNA aptamer.