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Methyl vinyl ketone (MVK), a volatile compound with photochemical activity, has received considerable attention in the fields of environmental chemistry and atmospheric chemistry. We explored the conformational stabilities of MVK in the neutral S0 and the cationic D0 states using conformer-specific vacuum ultraviolet mass-analyzed threshold ionization (VUV-MATI) spectroscopy, which provided identifiable vibrational spectra for cationic MVK conformers. Based on the origin bands of the two individual conformers of MVK identified in the MATI spectra under different supersonic expansion conditions, the accurate adiabatic ionization energies of the s-trans and the s-cis conformers were determined to be 77 867 ± 4 (9.6543 ± 0.0005 eV) and 78 222 ± 4 cm-1 (9.6983 ± 0.0005 eV), respectively. The identifiable vibrational spectra of the two cationic conformers were further confirmed using vibrational assignments based on the Franck-Condon fit. Accordingly, precise cationic structures of the MVK conformers could be determined. Selleckchem XL177A The structural changes of the two conformers upon ionization could be attributed to the removal of an electron from the highest occupied molecular orbital of each conformer, which consists of nonbonding molecular orbitals on the oxygen atom in the carbonyl group interacting with the σ orbitals in the molecular plane. Consequently, the s-trans conformer was preferred by 48 ± 18 and 403 ± 18 cm-1 in the neutral ground S0 and the cationic D0 states, respectively, which was supported by density-corrected density functional theory calculations and natural bond orbital analysis.Sunscreens are used to protect human skin against harmful UV radiation. Today there is a trend towards high sun protection factors (SPF) and good UVA protection. Methods for the assessment of SPF and UVA protection involve irradiation of the product, and the photostability properties of the sunscreen have an influence on its performance. Sunscreens often contain more than one UV filter. Some photolabile UV absorbers may be stabilized by the presence of other photostable UV-absorbers. Stabilization can be achieved just by a certain optical density due to the presence of such UV-filter substances. However, photostabilization may also be caused by quenching mechanisms, such as singlet-singlet or triplet-triplet energy transfer. Investigation of butyl methoxy dibenzoylmethane and ethylhexyl methoxycinnamate as photolabile sunscreens in the presence of either octocrylene or bis ethylhexyloxyphenol methoxyphenyl triazine showed that both mechanisms may apply. With the systems butyl methoxy dibenzoylmethane plus octocrylene and ethylhexyl methoxycinnamate plus bis ethylhexyloxyphenol methoxyphenyl triazine the quenching mechanism appears to be predominant.In the last decade, graphene has been frequently cited as one of the most promising materials for nanoelectronics. However, despite its outstanding mechanical and electronic properties, its use in the production of real nanoelectronic devices usually imposes some practical difficulties. This happens mainly due to the fact that, in its pristine form, graphene is a gapless material. We investigate theoretically the possibility of obtaining rectifying nanodevices using another carbon based two dimensional material, namely the graphenylene. This material has the advantage of being an intrinsic semiconductor, posing as a promising material for nanoelectronics. By doping graphenylene, one could obtain 2-dimensional p-n junctions, which can be useful for the construction of low dimensional electronic devices. We propose 2-dimensional diodes in which a clear rectification effect was demonstrated, with a conducting threshold of approximately 1.5 eV in direct bias and current blocking with opposite bias. During these investigations were found specific configurations that could result in devices with Zener-like behavior. Also, one unexpected effect was identified, which was the existence of transmission dips in electronic conductance plots. This result is discussed as a related feature to what was found in graphene nanoribbon systems under external magnetic fields, even though the external field was not a necessary ingredient to obtain such effect in the present case.A novel dearomatization/rearomatization/cyclization oxonium ylide trapping process is well developed via a dirhodium(ii) acetate and phosphoric acid cooperatively catalyzed multi-component reaction of diazo-ketones with alcohols and azonaphthalenes. This protocol provides an efficient route to synthesize N-substituted 1-amino-indole derivatives in good yield under mild reaction conditions.Topoisomerases are ubiquitous enzymes and important targets for DNA-oriented anticancer drugs. Two mitochondrion-targeted monofunctional platinum(ii) complexes, [Pt(ortho-PPh3CH2Py)(NH3)2Cl](NO3)2 (OPT) and [Pt(para-PPh3CH2Py)(NH3)2Cl](NO3)2 (PPT; PPh3 = triphenylphosphonium, Py = pyridine), show significant inhibition towards the activity of DNA topoisomerases in addition to their DNA binding and mitochondrial targeting capabilities. OPT exhibits strong cytotoxicity toward the human renal clear cell carcinoma 786-O and the murine prostate cancer RM-1 cell lines. The complex could bind to the minor groove of DNA, as well as DNA topoisomerases I and IIα, thereby acting as an inhibitor of topoisomerase I/IIα and causing DNA damage. The damage was evidenced by the enhanced expression of γ-H2AX, Chk1/2 phosphorylation, p53 and cell cycle arrest in the G2/M phase. In contrast, the inhibitory effect of PPT on DNA topoisomerases was largely limited to the isolated enzymes. The results demonstrate that the cellular inhibition of the complex towards the DNA topoisomerases positively correlated with its mitochondrial accumulation. Molecular docking provided more detailed structural insights into the interactions of OPT or PPT with DNA and topoisomerase I/IIα. The binding sites of OPT and PPT in topoisomerase-DNA complexes are different from each other. Aside from previously revealed DNA and mitochondrial targets, this study discovered new evidence that DNA topoisomerases may also serve as targets of monofunctional platinum(ii) complexes. For a multispecific platinum complex, strong DNA binding ability does not necessarily lead to potent cytotoxicity as other factors including the cell types, mitochondrial accumulation, and activity of DNA topoisomerases also affect the outcome of DNA damage.
Homepage: https://www.selleckchem.com/products/xl177a.html
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