The m 7 Gc ap is au nique nucleotide structure at the 5'-end of all eukaryotic mRNAs. The cap specificallyinteracts with numerous cellular proteins and participates in biological processes that are essential for cell growth and function. To provide small molecularp robest os tudy important cap-recognizing proteins, we synthesized m 7 Gn ucleotides labeled with fluorescent tags via the terminal phosph(on)ate group and studied how their emission properties changed upon protein binding or enzymaticc leavage. Only the pyrene-labeled compounds behaved as sensitive turn-on probes. Ap yrene-labeled m 7 GTP analogue showed up to eightfold enhanced fluorescencee mission upon binding to eukaryotic translation initiation factor 4E (eIF4E) and over 30-folde nhancementu pon cleavageb yd ecapping scavenger (DcpS) enzyme. These observations serveda st he basis for developing binding-and hydrolytic-activity assays. The assay utility was validated with previously characterizedl ibraries of eIF4E ligands and DcpS inhibitors. The DcpS assay was also appliedtostudy hydrolytic activity and inhibition of endogenous enzyme in cytoplasmic extracts from HeLa and HEK cells.

Photoinduced charge transfer is a crucial process in the operation of organic solar cells. In this work we used two spectroscopic techniques, namely, time-resolved photoluminescence and light-induced electron spin resonance, which directly detect this phenomenon in blends composed of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and two air-stable polyazomethines with different chemical structures, one with thiophene ring and cardo moieties (25Th-cardo) and one with three thiophene rings (2252Th-DMB). For both polymers we observed a photoluminescence with a maximum around 2 eV. In a mixture with PCBM, the photoluminescence of both polymers was quenched. At the same time, the photoluminescence of PCBM was enhanced in a mixture with 25Th-cardo, whereas it was similar to the photoluminescence of pure PCBM in the mixture with 2252Th-DMB. Moreover, for 2252Th-DMB:PCBM, two overlapping lines of electron spin resonance were detected under illumination, one originating from the positive polaron and another from the negative polaron. No trace of the analogue lines was seen for illuminated 25Th-cardo:PCBM. These differences were reflected also in an external quantum efficiency which increased from 0.3% for 25Th-cardo to 3% for 2252Th-DMB mixtures with PBCM. Experimental results are supported by the theoretical calculations of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels using the density functional theory method, and the presented observations are discussed within HOMO–LUMO models of the studied materials in the context of charge-transfer processes. Finally, the results addressed above are compared with those obtained for the P3HT:PCBM mixture typically used as donor–acceptor active layer in bulk heterojunction polymer solar cells.

7‐Methylguanine nucleotides labelled with pyrene were found to behave as sensitive turn‐on probes upon enzymatic cleavage or binding to specific proteins. This observation served as the basis for developing binding‐ and hydrolytic‐activity assays in a 96‐well format for two therapeutically‐relevant 7‐methylguanosine cap recognising proteins: translation initiation factor (eIF4E) and decapping enzyme (DcpS). A complex of eIF4E with pyrene labelled nucleotide is depicted on the cover. More information can be found in the Full Paper by J. Kowalska, J. Jemielity, et al. on page 6728.