BackgroundThe T box riboswitch controls bacterial transcription by structurally responding to tRNA aminoacylation charging ratios. Knowledge of the thermodynamic stability difference between two competing structural elements within the riboswitch, the terminator and the antiterminator, is critical for effective T box-targeted drug discovery.MethodsThe ΔG of aminoacyl tRNA synthetase (aaRS) T box riboswitch terminators and antiterminators was predicted using DINAMelt and the resulting ΔΔG (ΔGTerminator - ΔGAntiterminator) values were compared.ResultsAverage ΔΔG values did not differ significantly between the bacterial species analyzed, but there were significant differences based on the type of aaRS.ConclusionsThe data indicate that, of the bacteria studied, there is little potential for drug targeting based on overall bacteria-specific thermodynamic differences of the T box antiterminator vs. terminator stability, but that aaRS-specific thermodynamic differences could possibly be exploited for designing drug specificity.
This Guidance Document gives recommendations how to consider transformation products from soil photolysis (‘phototransformation products’) when modelling the predicted environmental concentrations in groundwater. It describes possible parameterisations of the photolytic pathway (i.e. the photolytic half‐life and the corresponding reference irradiation) in a tiered approach using the FOCUS‐PELMO model. Following the recommendations of the EFSA guidance (2014), separate half‐lives can be derived for the surface processes (k
fast
) and the biodegradation in the soil matrix (k
slow
) from field dissipation studies by using biphasic models. From field dissipation studies evaluated with biphasic kinetics, the k
fast
value can be considered representative for the photolytic degradation on soil surface for non‐volatile substances. This value should be determined after a time‐step normalisation according to irradiance data for the location and period of the field trial, to a reference irradiance of 100 W m
−2
. In case irradiance values are not available in the study, these values can be derived from databases such as AGRI4CAST or NASA, freely available in the Internet.
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