Electrical control of Förster energy transfer

Bringing together compounds of intrinsically different functionality, such as inorganic nanostructures and organic molecules, constitutes a particularly powerful route to creating novel functional devices with synergetic properties found in neither of the constituents. We introduce nanophotonic functional elements combining two classes of materials, semiconductor nanocrystals and dyes, whose physical nature arises as a superposition of the properties of the individual components. The strongly absorbing rod-like nanocrystals focus the incident radiation by photopumping the weakly absorbing dye via energy transfer. The CdSe/CdS nanorods exhibit a large quantum-confined Stark effect on the single-particle level, which enables direct control of the spectral resonance between donor and acceptor required for nanoscopic F?rster-type energy transfer in single nanorod-dye couples. With this far-field manipulation of a near-field phenomenon, the emission from single dye molecules can be controlled electrically. We propose that this effect could lead to the design of single-molecule optoelectronic switches providing building blocks for more complex nanophotonic circuitry.     

Ribosomal Protein S5e is Implicated in Translation Initiation through its Interaction with the N‐Terminal Domain of Initiation Factor eIF2α

A key step of translation initiation in eukaryotes is formation of the 48S preinitiation complex (PIC) containing the 40S ribosome, a set of eukaryotic initiation factors (eIFs), mRNA, and initiator Met‐tRNA interacting with mRNA start codon; however, the PIC structure remains substantially unknown. Here, we apply formaldehyde‐induced protein–protein crosslinks to identify contacts between ribosomal protein S5e (rpS5e, “e” stands for “eukaryotic”) and eIFs within the mammalian PIC, assembled on either model canonical or IRES‐containing mRNA. Using immunoblotting and mass spectrometry, we show that with both types of mRNA, rpS5e crosslinks to eIF2α. Comparative analysis of peptides resulting from trypsinolysis of the crosslinked proteins before and after crosslink reversal reveals crosslinked peptides in the N‐terminal parts of rpS5e and eIF2α. Application of these data to a model PIC structure obtained with the use of available structures indicates that eIF2α undergoes major conformation rearrangements to enable contacts of the factor with rpS5e. These contacts are suggested to maintain the correct positioning of eIF2α relative to other PIC components; this could be essential for start‐codon selection by the PIC.     

Transient kinetics of toluene partial oxidation over V/Ti oxide catalysts

Transient kinetics in the toluene oxidation over V/Ti oxide catalysts prepared by grafting and impregnation have been compared. V⁴⁺ cations are supposed to be the sites for the formation of electrophilic oxygen species participating in deep oxidation. Another oxygen species (probably nucleophilic) present on the oxidised catalyst surface are responsible for benzaldehyde formation. Selectivity of 80–100% can be obtained during the initial period of the reaction on the grafted catalysts in the presence of gaseous oxygen and during the interaction of toluene (without O₂ in the mixture) with partially reduced catalysts.