The 5′ cap consists of 7-methyl­guanosine (m7G) linked by a 5′–5′-triphosphate bridge to messenger RNA (mRNA) and acts as the master regulator of mRNA turnover and translation initiation in eukaryotes. Cap analogues that influence mRNA translation and turnover (either as small molecules or as part of an RNA transcript) are valuable tools for studying gene expression, which is often also of therapeutic relevance. Here, we synthesized a series of 15 dinucleotide cap (m7GpppG) analogues containing a 5′-phosphoro­thiolate (5′-PSL) moiety (i.e., an O-to-S substitution within the 5′-phospho­ester) and studied their biological properties in the context of three major cap-binding proteins: translation initiation factor 4E (eIF4E) and two decapping enzymes, DcpS and Dcp2. While the 5′-PSL moiety was neutral or slightly stabilizing for cap interactions with eIF4E, it significantly influenced susceptibility to decapping. Replacing the γ-phospho­ester with the 5′-PSL moiety (γ-PSL) prevented β-γ-pyrophosphate bond cleavage by DcpS and conferred strong inhibitory properties. Combining the γ-PSL moiety with α-PSL and β-phosphoro­thioate (PS) moiety afforded first cap-derived hDcpS inhibitor with low nanomolar potency. Susceptibility to Dcp2 and translational properties were studied after incorporation of the new analogues into mRNA transcripts by RNA polymerase. Transcripts containing the γ-PSL moiety were resistant to cleavage by Dcp2. Surprisingly, superior translational properties were observed for mRNAs containing the α-PSL moiety, which were Dcp2-susceptible. The overall protein expression measured in HeLa cells for this mRNA was comparable to mRNA capped with the translation augmenting β-PS analogue reported previously. Overall, our study highlights 5′-PSL as a synthetically accessible cap modification, which, depending on the substitution site, can either reduce susceptibility to decapping or confer superior translational properties on the mRNA. The 5′-PSL-analogues may find application as reagents for the preparation of efficiently expressed mRNA or for investigation of the role of decapping enzymes in mRNA processing or neuromuscular disorders associated with decapping.

A series of pyrimido[1,2-a]benzimidazole and α-cyanocinnamic acid derivatives have been synthesized in the reactions of Schiff bases 2–7 with selected nitriles containing an active methylene group: malononitrile 8–12, cyanoacetamide 13–16, benzyl cyanide 17–21, benzoylacetonitrile 22–24, cyanoacetate methyl ester 25–28 and benzylacetamide 29. The structures 8–29 were confirmed by the results of elementary analysis and their IR, 1H-, 13C-NMR and MS spectra. The products 8–29 of various chemical structure pyrimido[1,2-a] benzimidazole 8–12, 14–16, 17–21, 23–24, 26 and α-cyanocinnamic acid derivatives 13, 22, 25, 27, 28 were obtained, which are of interest for biological studies or which can be substrates for further synthesis. The selected compounds 10, 13, 14, 17, 19, 21, 23–25 and 28 were screened for their antiproliferative activity in vitro against neoplastic and normal cell lines. The most active two compounds were: 2-(o-bromophenylene)-3-cyano-4-phenyl-1,2-dihydropyrimido[1,2-a]benzimidazole (24) and 3-cyano-4-phenyl-2-(2,4-dimethoxyphenyl)-1,2-dihydropyrimido[1,2-a]benzimidazole (23). However, similarly like cisplatin used as the control, they showed no selectivity towards cancer cells, by inhibiting proliferation of normal mouse fibroblasts in similar manner.

The gold electrode surface has been functionalized by phenyl groups ending with aminoethyl or carboxyethyl entities. The functionalization was achieved by the electrochemical reduction of 4-aminoethylbenzene- or 4-carboxyethylbenzene-diazonium salts. The laccase layers were studied by polarization modulation infrared spectroscopy (PMIRRAS), linear sweep voltammetry, and electrochemical quartz microbalance. The kind of surface groups controlling the orientation of the enzyme on the surface was revealed by PMIRRAS. The orientation influenced the enzyme activity on its turn. The direct, mediatorless electrocatalytic current due to the oxygen reduction was observed starting from +0.60 V versus Ag/AgCl at pH 4.5 for laccase immobilized on the amine-ended layer. The observed potential value is close to the redox potential of the laccase T1 center. The electrocatalytic current values were equal to 4 mA/cm. Immobilization of laccase on the carboxyethyl groups leads to smaller electrocatalytic current values. The onset of the electrocatalytic current was down-shifted to +0.56 V.

No abstract

A different approach for synthesizing 5′ cap mimics to yield a novel class of dinucleotide cap analogues containing a triazole ring within the oligophosphate chain.