High efficiency two-photon uncaging coupled by the correction of spontaneous hydrolysis.

Two-photon (TP) uncaging of neurotransmitter molecules is the method of choice to mimic and study the subtleties of neuronal communication either in the intact brain or in slice preparations. However, the currently available caged materials are just at the limit of their usability and have several drawbacks. The local and focal nature of their use may for example be jeopardized by a high spontaneous hydrolysis rate of the commercially available compounds with increased photochemical release rate. Here, using quantum chemical modelling we show the mechanisms of hydrolysis and two-photon activation, and synthesized more effective caged compounds. Furthermore, we have developed a new enzymatic elimination method removing neurotransmitters inadvertently escaping from their compound during experiment. This method, usable both in one and two-photon experiments, allows for the use of materials with an increased rate of photochemical release. The efficiency of the new compound and the enzymatic method and of the new compound are demonstrated in neurophysiological experiments.

Determination of steroids in the dissolved and in the suspended phases of wastewater and Danube River samples by gas chromatography, tandem mass spectrometry.

In this paper, a new working approach is described for the analysis of steroids as environmental water pollutants. As novelty to the field, steroids were identified and quantified both in the dissolved and in the suspended phases, as their trimethylsilyl-(oxime)-ether derivatives, applying a recently developed tandem gas chromatographic mass spectrometric (GC-MS/MS) method, applying multiple reaction monitoring (MRM) acquisition, suitable for their quantitation in the low ng/L level, in wastewater and in Danube River samples. In addition to the analysis of filtrates obtained by the common solid phase extraction (SPE) enrichment, even the insoluble, isolated by filtration prior to the SPE, and usually discarded part of steroids were identified and quantified, simultaneously, for the first time. For this purpose a new, time, labor, cost efficient and quantitative, ultrasound assisted extraction process was developed. Reproducibility, reliability and practical utility of the ultrasound assisted extraction process were proved by the proportionality of the extracted suspended steroids obtained from different sample volumes: prepared from 0.5L and 1.0 L influent wastewater, as well as from 3 L, 5 L and 10 L Danube River water samples. Steroids' concentrations, identified and quantified in suspended conditions, showed proportionality, characterized with the relative standard deviation percentages (RSD%) of analyses: varying in case of Danube River water in the range of 0.92-6.0%, with an average of 4.10% RSD, while in the case of influent wastewater in the range of 1.59-5.8%, with an average of 4.03% RSD. Partition of steroids, between the dissolved and suspended phases of influent and effluent wastewaters and river water samples, meaning, the total amounts of steroids that the ecosystem is liable to, were defined in river water samples for the first time. Distribution of found steroids revealed that their considerable and/or overwhelming part (relating to their total amounts), are present in suspended phases: in average, 71% from wastewater and 64% from Danube River samples.