A Usual G‐Protein‐Coupled Receptor in Unusual Membranes

G‐protein‐coupled receptors (GPCRs) are the largest family of membrane‐bound receptors and constitute about 50 % of all known drug targets. They offer great potential for membrane protein nanotechnologies. We report here a charge‐interaction‐directed reconstitution mechanism that induces spontaneous insertion of bovine rhodopsin, the eukaryotic GPCR, into both lipid‐ and polymer‐based artificial membranes. We reveal a new allosteric mode of rhodopsin activation incurred by the non‐biological membranes: the cationic membrane drives a transition from the inactive MI to the activated MII state in the absence of high [H⁺] or negative spontaneous curvature. We attribute this activation to the attractive charge interaction between the membrane surface and the deprotonated Glu134 residue of the rhodopsin‐conserved ERY sequence motif that helps break the cytoplasmic “ionic lock”. This study unveils a novel design concept of non‐biological membranes to reconstitute and harness GPCR functions in synthetic systems.     

Mechanistic Studies on Photoinduced Catalytic Olefin Migration Reactions at the Pd(II) Centers of a Porous Crystal,Metal-Macrocycle Framework

Porous crystals with well-defined active metal centers on the pore surface have high potential as heterogeneous metal catalysts. We have recently demonstrated that a porous molecular crystal, metal-macrocycle framework (MMF), catalyzes olefin migration reactions by photoactivation of its Pd^IICl₂ moieties exposed on the crystalline channel surface. Herein we report a mechanistic study of the photoinduced olefin migration reactions at the Pd^II active centers of MMF. Several experiments, including a deuterium scrambling study, revealed that olefin migration is catalyzed via an alkyl mechanism by in situ generated Pd−H species on the channel surface during photoirradiation. This proposed mechanism was further supported by DFT and ONIOM calculations.     

In‐Depth Studies on Rapid Photochemical Activation of Various Sol–Gel Metal Oxide Films for Flexible Transparent Electronics

Despite intensive research on photochemical activation of sol–gel metal oxide materials, the relatively long processing time and lack of deep understanding of the underlying chemical courses have limited their broader impact on diverse materials and applications such as thin‐film electronics, photovoltaics, and catalysts. Here, in‐depth studies on the rapid photochemical activation of diverse sol–gel oxide films using various spectroscopic and electrical investigations for the underlying physicochemical mechanism are reported. Based on the exhaustive chemical and physical analysis, it is noted that deep ultraviolet‐promoted rapid film formation such as densification, polycondensation, and impurity decomposition is possible within 5 min via in situ radical‐mediated reactions. Finally, the rapid fabrication of all‐solution metal oxide thin‐film‐transistor circuitry, which exhibits stable and reliable electrical performance with a mobility of >12 cm² V^?1 s^?1 and an oscillation frequency of >650 kHz in 7‐stage ring oscillator even after bending at a radius of <1 mm is demonstrated.     

Artificial Light‐Gated Catalyst Systems

Having control over an entity or even an entire process is arguably the ultimate demonstration of its understanding and it will enable its potential to be fully exploited. With this in mind, chemists have not only been creating and optimizing a myriad of different catalysts for most (relevant) chemical reactions over the past decades, but have recently started to implement controlling elements into the catalyst design. These incorporated gates operate upon exposure to suitable control stimuli, and light represents perhaps the scientifically and technologically most attractive stimulus. In principle, irradiation can thereby induce activity and selectivity in a given catalyst system with high spatial and temporal control, leading to an overall localization and amplification of an optical signal and translation into chemical action. While nature has developed and utilized this concept, in particular in the processes of vision and photomovement, such artificial photocontrolled catalyst systems offer unique opportunities and have high potential for future applications. In this Review, we outline the general concept of light‐gated catalysis based on photocaged and also photoswitchable systems, and discuss relevant examples of the past and recent literature.     

Two-step photoactivation of hematoporphyrin by excimer-pumped dye-laser pulses

The selective excitation of high lying singlet or triplet states of hematoporphyrin has been achieved using high peak-power nanosecond pulses generated by excimer-pumped dye lasers. The interaction involves two steps: a pulse at 630 nm raises the molecules to the S1 state and a second one, at 481 nm, further excites them either to a higher singlet state if shed simultaneously or to a triplet state higher in energy than T1 if it arrives delayed with respect to the pulse at 630 nm by a time interval longer than the S1 lifetime. Photodegradation of L-tryptophan (100 microM in 30vol.%methanol-70vol.% buffer, pH 7.4) sensitized by 21 microM hematoporphyrin is reported. While a pure type-II mechanism, which obeys the time-intensity reciprocity law up to peak-intensity values of about 20 MW cm-2, is photosensitized by pulses at 630 nm, strong non-linearities are found for pulsed irradiation at both 630 nm and 481 nm, i.e. when the sensitizer is pumped to high lying singlet states and when it is pumped to high lying triplet states. The dependence of the subsequent reactions on the presence of oxygen and their competition with the photodynamic action has been investigated; in particular, a pathway was observed in which an electron was photoejected from a hematoporphyrin high energy triplet, showing maximum efficiency when the pulses were delayed by 16.4 ns.     

Determination of Imidacloprid and metabolites by liquid chromatography with an electrochemical detector and post column photochemical reactor

A procedure for the determination of Imidacloprid and its main metabolites was set up by means of liquid chromatography with an electrochemical detector and post-column photochemical reactor (LC-hν-ED). Sample clean-up was developed for bees, filter paper and maize leaves. Chromatographic conditions were based on a reversed-phase C-18 column operated by phosphate buffer 50 mM/CH₃CN (80/20, v/v) at pH 2.9. Detection of Imidacloprid and its metabolites was performed at a potential of 800 mV after photoactivation at 254 nm. Compared to conventional techniques such as gas chromatography/mass spectrometry (GC/MS) or LC coupled to other detectors, the present method allows simultaneous trace-level determination of both Imidacloprid (0.6 ng ml⁻¹) and its main metabolites (2.4 ng ml⁻¹).