Selective degradation of styrene-contained plastics catalyzed by iron under visible light

Efficient degradation of plastics, the vital challenge for a sustainable future, stands in need of better chemical recycling procedures that help produce commercially valuable small molecules and redefine plastic waste as a rich source of chemical feedstock. However, the corresponding chemical recycling methods, while being generally restricted to polar polymers, need improvement. Particularly, degradation of chemical inert nonpolar polymers, the major constitutes of plastics, are reported to have suffered from low selectivity and very harsh transformation conditions. Herein, we report an efficient method for the selective degradation of styrene-contained plastics under gentle conditions through oxidative multiple sp3 C-C bond cleavage. The unpresented procedure is catalyzed with inexpensive iron salts under visible light, using oxygen as the green oxidant. Furthermore, simple iron salts can be used to degrade plastics in the absence of solvent under natural conditions, highlighting the potential application of iron salts as additives for degradable plastics

Cobalt catalyzed practical hydroboration of terminal alkynes with time-dependent stereoselectivity

Stereodefined vinylboron compounds are important organic synthons. The synthesis of E-1-vinylboron compounds typically involves the addition of a B-H bond to terminal alkynes. The selective generation of the thermodynamically unfavorable Z-isomers remains challenging, necessitating improved methods. Here, such a proficient and cost-effective catalytic system is introduced, comprising a cobalt salt and a readily accessible air-stable CNC pincer ligand. This system enables the transformation of terminal alkynes, even in the presence of bulky substituents, with excellent Z-selectivity. High turnover numbers (>1,600) and turnover frequencies (>132,000 h⁻¹) are achieved at room temperature, and the reaction can be scaled up to 30 mmol smoothly. Kinetic studies reveal a formal second-order dependence on cobalt concentration. Mechanistic investigations indicate that the alkynes exhibit a higher affinity for the catalyst than the alkene products, resulting in exceptional Z-selective performance. Furthermore, a rare time-dependent stereoselectivity is observed, allowing for quantitative conversion of Z-vinylboronate esters to the E-isomers.ISSN:2041-172

Dynamics and Cell-Type Specificity of the DNA Double-Strand Break Repair Protein RecN in the Developmental Cyanobacterium Anabaena sp. Strain PCC 7120.

DNA replication and repair are two fundamental processes required in life proliferation and cellular defense and some common proteins are involved in both processes. The filamentous cyanobacterium Anabaena sp. strain PCC 7120 is capable of forming heterocysts for N2 fixation in the absence of a combined-nitrogen source. This developmental process is intimately linked to cell cycle control. In this study, we investigated the localization of the DNA double-strand break repair protein RecN during key cellular events, such as chromosome damaging, cell division, and heterocyst differentiation. Treatment by a drug causing DNA double-strand breaks (DSBs) induced reorganization of the RecN focus preferentially towards the mid-cell position. RecN-GFP was absent in most mature heterocysts. Furthermore, our results showed that HetR, a central player in heterocyst development, was involved in the proper positioning and distribution of RecN-GFP. These results showed the dynamics of RecN in DSB repair and suggested a differential regulation of DNA DSB repair in vegetative cell and heterocysts. The absence of RecN in mature heterocysts is compatible with the terminal nature of these cells

Movement of RecN in vegetative cells displayed by time-lapse imaging.

<p>The dynamic localization of RecN focus is demonstrated by time-lapse microscopy from the RG-W. Cells were photographed at 3–4 h intervals. Images on the right were taken in bright field and those on the left were taken in fluorescence respectively in 0, 3, 6, and 10 h. The newborn foci were also marked. Images were taken using a Nikon Eclipse 80i microscope. Scale bars correspond to 1 μm.</p

RecN appears as a single discrete globular focus in newly formed heterocyst and disappears in mature ones.

<p>(A) RecN-GFP focus in heterocyst (white arrow). (B) Rates (in percentage) of heterocysts with RecN–GFP foci after the starvation of combined nitrogen. (C) Western blotting analysis of protein extracts from vegetative cells or enriched heterocysts using anti-RecN antiserum. Lanes 1 and 2: extracts from vegetative cell in 0 and 12 h after nitrogen deprivation; Lanes 3, 4 and 5: extracts from heterocyst in 24, 48 and 72 h after nitrogen deprivation. (D) High concentration of MMC did not lead to the reformation of RecN-GFP foci in mature heterocysts. After 24 h deprivation of combined nitrogen, 4 μg/mL MMC was added into the medium for 3-day cultivation and then the photographs were captured. The white arrows indicate heterocysts. Photographs were taken by using an Olympus FV1000 confocal microscope. Cells were stained with DAPI (blue). The red fluorescence is the fluorescence of photosynthetic pigment. Scale bars correspond to 1 μm.</p

Segregation of RecN foci during vegetative cell division.

<p>(A) The method used to quantify the relative distance between foci along the cell division axis. In the formula, “a” means a cell inheriting the original RecN focus after division; “b” means a cell with both an original and a newborn RecN focus. Photographs were captured by using an Olympus FV1000 confocal microscope. Cells were stained with DAPI (blue). Scale bars correspond to 1 μm. (B) Cell number distribution obtained according to the relative distance. (C) Original and newborn RecN foci usually were nearly symmetrically distributed along the cell division axis. Photograph by using a Nikon Eclipse 80i microscope, in the fluorescence and bright fields. Scale bars correspond to 1 μm.</p

RecN forms a single discrete globular focus in vegetative cells.

<p>(A) The three types of vegetative cells divided according to the cell division stages. (B) Localization of RecN-GFP was determined according to its relative position along the x axis and y axis. (C). The locations of the foci in the three types of vegetative cells. The coordinate 0 is the center of the cell. (D) The distributions (in percentage) of the three types of vegetative cells at the relative position of the X-axis. The dynamic localization of RecN-GFP foci was observed with an Olympus FV1000 confocal microscope. Cells were stained with DAPI (blue). Scale bars correspond to 1 μm.</p

RecN focus is close to the center of the cell treated with MMC.

<p>(A) Most RecN-GFP foci are colocalized with nucleoid at the center area of cells when treated with 2 μg/mL MMC. (B, C) RecN-GFP foci and nucleoids were colocalized at the position of cell plate between two daughter cells in dividing cell pairs. (D) RecN-GFP focus was localized in one of the daughter cells when the chromosome was segregated at the later period of cell cycle after MMC treatment. (E) The white arrows indicated that in a few cells, RecN–GFP foci were not colocalized with the chromosome at the central areas (5% in total, n = 196). (F) Nucleoids were more compacted and the number of RecN-GFP foci increased in some cells (white arrows) (21% of cell in a total, n = 213) after the treatment with 4 μg/mL MMC. Photographs were taken by using an Olympus FV1000 confocal microscope. Cells were stained with DAPI (blue). Each photograph involved 3 different channels for DAPI (in blue) GFP (in green) fluorescence and bright field. Scale bars correspond to 1 μm.</p

Determination of Solubility of cAMPNa in Water + (Ethanol, Methanol, and Acetone) within 293.15–313.15 K

The solubility of adenosine 3′,5′-cyclic monophosphate sodium (cAMPNa) in mixed solvents (water+ethanol, water+methanol, and water+acetone) was measured within 293.15−313.15 K under atmospheric pressure. The (CNIBS)/Redlich−Kister model and the modified Apelblat equation were respectively applied to correlate the solubility data to evaluate the effect of the compositional ratio of the organic solvent and the temperature on the solubility in binary solvents, and satisfactory simulation results were obtained. The solubility of cAMPNa was maximal in pure water and markedly diminished at all evaluated temperatures as the mole fraction of the organic solvent in the aqueous mixture increased. The thermodynamic functions for cAMPNa dissolution in the three solvent mixtures were obtained from the solubility data using the van’t Hoff and Gibbs equations, and the dissolution behavior was discussed. Dissolution of cAMPNa was endothermic and nonspontaneous in all cases, and the enthalpy was the major contributing force to the Gibbs energy

Comparative study of different algae pyrolysis using photoionization mass spectrometry and gas chromatography/mass spectrometry

Pyrolysis of three algae, i.e. Nannochloropsis, Spirulina, and Sargassum was investigated by the combination of fixed bed pyrolysis with gas chromatography/mass spectrometry and pyrolysis photoionization mass spectrometry (py-PIMS) methods. Lipid, protein, and carbohydrate are the dominant components of the three algae, respectively. Mass spectrum profiles at different temperatures (400 ?C, 500 ?C, 600 ?C, and 700 ?C), temperature-programmed and time-evolved profiles of major products were measured. The decomposition reaction of fatty acids led to the formation of alkanes and alkenes. Aromatic compounds came from the nitrogencontaining compounds derived from protein and dehydrogenation of cyclic alkanes and alkenes through the Diels?Alder reaction from unsaturated fatty acids. Polycyclic nitrogenous compounds can be generated by the ring condensation reactions of monocyclic N-heterocyclic compounds. Lipids may interfere with the decomposition of protein. The presence of carbohydrates facilitates the formation of N-heterocyclic compounds. Two formation pathways of 1,4:3,6-dianhydro-?-D-glucopyranose and 2,4-dimethylfuran from hemicellulose and cellulose at different temperatures were observed