Механизм люминесцентного хемосенсорного отклика в хелатах европия(III)

There were studied the luminescent chemosensory properties of Eu(III) carboxylatodibenzoylmethanates with acetic and acrylic acids while the interaction with ammonia vapors. Quantitative measurements of the optical response showed that with an increase in the analyte concentration in the range of 3-330 ppm, a linear increase in the luminescence intensity of europium(III) is observed. The reversibility of the luminescent response was established, the limit of detection of ammonia was 3 ppm. The mechanism of the optical effect is revealed by the method of quantum chemical modeling: the interaction of ammonia with the sensor leads to the formation of a rigid structural fragment of H2O–NH3, which blocks the quenching effect of high-frequency OH vibrations on luminescence. The studied chemosensors have high sensitivity and selectivity and, thus, can be promising for creating ammonia detection sensors for food safety control and environmental monitoring.

POLYMERIZATION OF 8-ACETOXYTETRACYCLO[4.4.12,5.17,10.01,6]DODEC-3-ENE AND ITS COPOLYMERIZATION WITH ACRYLIC ACIDS

The reaction of radical polymerization of 8-acetoxytetracyclo[4.4.12,5.17,10.01,6]dodec-3-ene as well as its copolymerization with methacrylic acids in the presence of BF3·OEt2 in bulk and in the medium of organic solvent, particularly in benzene was investigated. The influence of various factors: the amount of catalyst, temperature and reaction time on the process of polymerization, as well as the influence of the monomer ratio on the copolymerization process was studied. The structure of the obtained homo- and copolymers was confirmed by IR spectroscopy and the thermal stability of the obtained polymers and their cured products was studied

Directed evolution of prenylated FMN-dependent Fdc supports efficient in vivo isobutene production

Isobutene is a high value gaseous alkene used as fuel additive and a chemical building block. As an alternative to fossil fuel derived isobutene, we here develop a modified mevalonate pathway for the production of isobutene from glucose in vivo. The final step in the pathway consists of the decarboxylation of 3-methylcrotonic acid, catalysed by an evolved ferulic acid decarboxylase (Fdc) enzyme. Fdc belongs to the prFMN-dependent UbiD enzyme family that catalyses reversible decarboxylation of (hetero)aromatic acids or acrylic acids with extended conjugation. Following a screen of an Fdc library for inherent 3-methylcrotonic acid decarboxylase activity, directed evolution yields variants with up to an 80-fold increase in activity. Crystal structures of the evolved variants reveal that changes in the substrate binding pocket are responsible for increased selectivity. Solution and computational studies suggest that isobutene cycloelimination is rate limiting and strictly dependent on presence of the 3-methyl group.