Read by QxMD icon Read


William W Parson
Rate constants for photochemical charge separation and recombination in a zinc-porphyrin-benzoquinone cyclophane are calculated by an approach that was developed recently to include effects of vibrational dephasing and relaxation and to reduce the dependence on freely adjustable parameters. The theory is extended to treat the rate of vibrational relaxation individually for each vibrational sublevel of the initial charge-transfer product. Quantum-mechanical/molecular-mechanical simulations of the reactions in iso-octane, toluene, dichloromethane and acetonitrile suggest that charge separation occurs at conical intersections in the two more polar solvents, but at avoided crossings in the nonpolar solvents...
March 20, 2018: Journal of Physical Chemistry. B
Mathieu Lesieur, Christophe Genicot, Patrick Pasau
A continuous mesofluidic process has been developed for benzylic C-H oxidation with moderate to good yields using a photocatalyst (riboflavin tetraacetate, RFT) activated by a UV lamp and an iron additive [Fe(ClO4 )2 ] via incorporation of singlet oxygen (1 O2 ) for the direct formation of oxidized C═O or CH-OH compounds.
March 20, 2018: Organic Letters
Chalupat Jindakun, Sheng-Ying Hsieh, Jeffrey W Bode
Commercially available tin amine protocol (SnAP) reagents provide a simple approach to the synthesis of a wide variety of saturated N-heterocycles from aldehydes. In this report, we disclose that the copper(II) promoter and hexafluoroisopropanol can be replaced by photocatalytic conditions using Ir[dF(CF3 )ppy]2 (dtbbpy)PF6 in CH3 CN. Continuous flow photochemical conditions provide a clean, scalable approach to valuable products including morpholines, piperazines, thiomorpholines, diazepanes, and oxazepanes from aldehyde starting materials...
March 20, 2018: Organic Letters
Toru Amaya, Hayato Fujimoto, Takahiro Tanaka, Toshiyuki Moriuchi
The macrocycle 1 containing four photoresponsive fluorenylidene moieties was designed. The EZEZ form of 1, 1EZEZ , was selectively produced. Reversible photochemical isomerization between 1EZEZ and 1ZZZZ was achieved, the extent of which was dependent on the light source used. Furthermore, the intermediate 1EZZZ was selectively isomerized to 1ZZZZ thermally and photochemically.
March 20, 2018: Organic Letters
Margherita Maiuri, Johanna Brazard
During the last two decades, 2D optical techniques have been extended to the visible range, targeting electronic transitions. Since the report of the very first 2D electronic measurement (Hybl et al. in J Chem Phys 115:6606-6622, [2001]), two-dimensional electronic spectroscopy (2DES) has allowed fundamentally new insights into the structure and dynamics of condensed-phase systems (Ginsberg et al. in Acc Chem Res 42:1352-1363, 2009; Jonas in Annu Rev Phys Chem 54:425-463, 2003), producing experiments that measure correlations among electronic states of an absorbing species within complex systems...
March 20, 2018: Topics in Current Chemistry (Journal)
Koichiro Takao, Satoru Tsushima
The carbonate ion is an effective quencher of uranyl(vi) luminescence and makes uranyl(vi) tricarbonate barely luminescent and photochemically inactive. We demonstrate here that photoexcited uranyl(vi) tricarbonate, *[UVIO2(CO3)3]4-, can however oxidize borohydrides (BH3X-, X = H, CN) to give boric acid and H2 gas, reducing itself to [UVO2(CO3)3]5-. This hypothesis was supported by UV-vis and NMR spectroscopy as well as quantum chemical calculations. The charge transfer states associated with photoreduction processes were modelled by density functional theory calculations...
March 20, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
C Schnedermann, X Yang, M Liebel, K M Spillane, J Lugtenburg, I Fernández, A Valentini, I Schapiro, M Olivucci, P Kukura, R A Mathies
Vibronic coupling is key to efficient energy flow in molecular systems and a critical component of most mechanisms invoking quantum effects in biological processes. Despite increasing evidence for coherent coupling of electronic states being mediated by vibrational motion, it is not clear how and to what degree properties associated with vibrational coherence such as phase and coupling of atomic motion can impact the efficiency of light-induced processes under natural, incoherent illumination. Here, we show that deuteration of the H11 -C11 =C12 -H12 double-bond of the 11-cis retinal chromophore in the visual pigment rhodopsin significantly and unexpectedly alters the photoisomerization yield while inducing smaller changes in the ultrafast isomerization dynamics assignable to known isotope effects...
March 19, 2018: Nature Chemistry
Tomas Solomek, Prince Ravat, Zhongyu Mou, Miklos Kertesz, Michal Juricek
We demonstrate that the electrocyclic (EC) ring-closure of cethrene in solution proceeds in a conrotatory mode both thermally and photochemically. The facile photochemical EC process promises that cethrene could serve as an efficient chiroptical switch operated solely by light. As for the thermally activated EC reaction, a low reaction barrier and a solvation effect on the EC rate indicate that the C2-symmetric pathway predicted by DFT calculations might not be the correct mechanism. Instead, we argue that the molecular symmetry decreases along the reaction coordinate as a consequence of the low-energy singlet excited state in this diradicaloid molecule, which might lead to a lower activation energy in accord with that determined through kinetic studies...
March 19, 2018: Journal of Organic Chemistry
Anouk S Lubbe, Qing Liu, Sanne J Smith, Jan Willem de Vries, Jos C M Kistemaker, Alex H De Vries, Ignacio Faustino, Zhuojun Meng, Wiktor Szymanski, Andreas Herrmann, Ben L Feringa
Reversible control over the functionality of biological systems via external triggers may be used in future medicine to reduce the need for invasive procedures. Additionally, externally regulated biomacromolecules are now considered as particularly attractive tools in nanoscience and the design of smart materials, due to their highly programmable nature and complex functionality. Incorporation of photoswitches into biomolecules, such as peptides, antibiotics and nucleic acids, has generated exciting results in the past few years...
March 18, 2018: Journal of the American Chemical Society
Huan He, Bin Huang, Gen Fu, Dan Xiong, Zhixiang Xu, Xinhao Wu, Xuejun Pan
The photochemical conversion and microbial transformation of pollutants mediated by dissolved organic matter (DOM), including 17α-ethinylestradiol (EE2), are often accompanied in natural water. However, there are few studies to explore the connection and mechanism between the two processes. This research aims to investigate the mechanism of DOM after electrochemically modification mediated EE2 combining photodegradation and biodegradation in the environment and it want to explain the natural phenomena of DOM after electrochemical advanced treatment entering the water environment mediated EE2 natural degradation...
March 12, 2018: Water Research
Alexandra J Townsend, Francesco Saccon, Vasco Giovagnetti, Sam Wilson, Petra Ungerer, Alexander V Ruban
Non-photochemical quenching (NPQ) of chlorophyll fluorescence is the process by which excess light energy is harmlessly dissipated within the photosynthetic membrane. The fastest component of NPQ, known as energy-dependent quenching (qE), occurs within minutes, but the site and mechanism of qE remain of great debate. Here, the chlorophyll fluorescence of Arabidopsis thaliana wild type (WT) plants was compared to mutants lacking all minor antenna complexes (NoM). Upon illumination, NoM exhibits altered chlorophyll fluorescence quenching induction (i...
March 13, 2018: Biochimica et Biophysica Acta
Isabel Aparici-Espert, Miguel A Miranda, Virginie Lhiaubet-Vallet
Photosensitization by drugs is a problem of increasing importance in modern life. This phenomenon occurs when a chemical substance in the skin is exposed to sunlight. Photosensitizing drugs are reported to cause severe skin dermatitis, and indeed, it is generally advised to avoid sunbathing and to apply sunscreen. In this context, the nonsteroidal anti-inflammatory drug (NSAID) diclofenac is a photosensitive drug, especially when administered in topical form. In this work, efforts have been made to design and study an innovative pro-drug/pro-filter system containing diclofenac and the UVA filter avobenzone in order to develop a safer use of this topical drug...
March 16, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Nigel Scrutton, Uzma Choudry, Derren Heyes, Samantha Hardman, Michiyo Sakuma, Igor Sazanovich, Joyce Woodhouse, Eugenio De La Mora, Martin Pederson, Michael Wulff, Martin Weik, Giorgio Schiro
Phytochromes are bilin-containing photoreceptors that are typically sensitive to the red / far-red region of the visible spectrum. Recently phytochromes from certain eukaryotic algae have become attractive targets for optogenetic applications because of their unique ability to respond to multiple wavelengths of light. Here, we have used a combination of time-resolved spectroscopy and structural approaches across picosecond to second timescales to map photochemical mechanisms and structural change in this atypical group of phytochromes...
March 15, 2018: Chembiochem: a European Journal of Chemical Biology
Andreu Presa, Guillem Vázquez, Leoní A Barrios, Olivier Roubeau, Luís Korrodi-Gregório, Ricardo Pérez-Tomás, Patrick Gamez
The development of photoactivatable metal complexes with potential anticancer properties is a topical area of current investigation. Photoactivated chemotherapy using coordination compounds is typically based on photochemical processes occurring at the metal center. In the present study, an innovative approach is applied that takes advantage of the remarkable photochemical properties of diarylethenes. Following a proof-of-concept study with two complexes, namely, C1 and C2, a series of additional platinum(II) complexes from dithienylcyclopentene-based ligands was designed and prepared...
March 15, 2018: Inorganic Chemistry
Jinxu Gao, Adelphe Mfuh, Yuka Amako, Christina M Woo
Many therapeutics elicit cell-type specific polypharmacology that is executed by a network of molecular recognition events between a small molecule and the whole proteome. However, measurement of the structures that underpin the molecular associations between the proteome and even common therapeutics, such as the nonsteroidal anti-inflammatory drugs (NSAIDs), is limited by the inability to map the small molecule interactome. To address this gap, we developed a platform termed small molecule interactome mapping by photoaffinity labeling (SIM-PAL) and applied it to the in cellulo direct characterization of specific NSAID binding sites...
March 15, 2018: Journal of the American Chemical Society
Sindhu Kancherla, Marianne Lorentzen, Victor Snieckus, Kåre Bredeli Jørgensen
A general method for the regioselective synthesis of a series of ortho-substituted chrysenyl N,N-diethyl-O-carbamates by the directed ortho metalation (DoM) strategy is reported. The starting O-carbamates were prepared from corresponding chrysenols, available by oxidative photochemical cyclization or directed remote metalation tactics. Chrysen-1-yl and chrysene-3-yl ring site selectivity of directed ortho metalation (DoM) and anionic ortho Fries rearrangement (AoF) protocols, with s-BuLi/TMEDA, followed by electrophilic quench using a selection of electrophiles, were observed leading to new chrysenyl derivatives...
March 15, 2018: Journal of Organic Chemistry
Katarzyna Brach, Akiko Hatakeyama, Claude Nogues, Joanna Olesiak-Banska, Malcolm Buckle, Katarzyna Matczyszyn
The anisotropic shape of DNA molecules allows them to form lyotropic liquid crystals (LCs) at high concentrations. This liquid crystalline arrangement is also found in vivo (e.g., in bacteriophage capsids, bacteria or human sperm nuclei). However, the role of DNA liquid crystalline organization in living organisms still remains an open question. Here we show that in vitro, the DNA spatial structure is significantly changed in mesophases compared to non-organized DNA molecules. DNA LCs were prepared from pBluescript SK (pBSK) plasmid DNA and investigated by photochemical analysis of structural transitions (PhAST)...
March 14, 2018: Scientific Reports
Andreas Carstensen, Andrei Herdean, Sidsel Birkelund Schmidt, Anurag Sharma, Cornelia Spetea, Mathias Pribil, Søren Husted
Phosphorus (P) is an essential macronutrient, and P deficiency limits plant productivity. Recent work showed that P deficiency affects electron transport to photosystem I (PSI), but the underlying mechanisms are unknown. Here, we present a comprehensive biological model describing how P deficiency disrupts the photosynthetic machinery and the electron transport chain through a series of sequential events in barley (Hordeum vulgare). Phosphorus deficiency reduces the orthophosphate (Pi) concentration in the chloroplast stroma to levels that inhibit ATP synthase activity...
March 14, 2018: Plant Physiology
Weize Song, Haifeng Jia, Zhilin Li, Deliang Tang
Urban air pollutant distribution is a concern in environmental and health studies. Particularly, the spatial distribution of NO2 and PM2.5 , which represent photochemical smog and haze pollution in urban areas, is of concern. This paper presents a study quantifying the seasonal differences between urban NO2 and PM2.5 distributions in Foshan, China. A geographical semi-variogram analysis was conducted to delineate the spatial variation in daily NO2 and PM2.5 concentrations. The data were collected from 38 sites in the government-operated monitoring network...
March 11, 2018: Science of the Total Environment
Wei Huang, Ying-Jie Yang, Shi-Bao Zhang, Tao Liu
In higher plants, moderate photoinhibition of photosystem II (PSII) leads to a stimulation of cyclic electron flow (CEF) at low light, which is accompanied by an increase in the P700 oxidation ratio. However, the specific role of CEF stimulation at low light is not well known. Furthermore, the mechanism underlying this increase in P700 oxidation ratio at low light is unclear. To address these questions, intact leaves of the shade-adapted plant Panax notoginseng were treated at 2258 μmol photons m-2 s-1 for 30 min to induce PSII photoinhibition...
2018: Frontiers in Plant Science
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"