Molecular basis of human ATM kinase inhibition.

Human checkpoint kinase ataxia telangiectasia-mutated (ATM) plays a key role in initiation of the DNA damage response following DNA double-strand breaks. ATM inhibition is a promising approach in cancer therapy, but, so far, detailed insights into the binding modes of known ATM inhibitors have been hampered due to the lack of high-resolution ATM structures. Using cryo-EM, we have determined the structure of human ATM to an overall resolution sufficient to build a near-complete atomic model and identify two hitherto unknown zinc-binding motifs. We determined the structure of the kinase domain bound to ATPγS and to the ATM inhibitors KU-55933 and M4076 at 2.8 Å, 2.8 Å and 3.0 Å resolution, respectively. The mode of action and selectivity of the ATM inhibitors can be explained by structural comparison and provide a framework for structure-based drug design.

Mathematical modelling of small wastewater treatment plants: power and limitations.

Although mathematical modelling of biological wastewater treatment processes has proved to be valuable for large-scale WWTPs (wastewater treatment plants) little experience has been acquired in the mathematical modelling of small wastewater treatment plants. This paper seeks to evaluate the applicability of mathematical modelling on small systems, which are characterized by high fluctuations in organic and hydraulic loads and little possibility for control. In order to achieve this, the paper examines the different steps in a general modelling protocol. One important bottleneck for the general use of mathematical modelling of small systems that emerges is the frequent sampling and many analyses needed for characterization of the flows while its applicability is limited. On the other hand, the determination of the model structure of a small WWTP can be quite valuable. Experiments show that tracer tests should include tests with a highly varying influent flow rate to spot independent small internal flows as these can have a significant impact on the behaviour of peak concentrations throughout the system. In addition, the model structure determination can provide useful information on dead zones, short-circuiting and mixing behaviour in the plant.

Performance of a submerged aerated filter and a rotating biological contactor under dynamic loading conditions.

Two types of small wastewater treatment systems were studied for their performance under normal conditions, including the hydraulic peak flows associated with small systems connected to just one house. Furthermore, the systems were subjected to a 7-day starvation period to simulate the effect of a holiday from home. The systems studied are (1) a combined submerged aerated filter-activated sludge system and (2) a rotating biological contactor system. Both the organic removal and the nitrification process were closely monitored. During normal operation, very good treatment results were achieved. The combined SAF-AS system realized 95% BOD removal, 88% COD removal and 94% NH4-N removal. The RBC system removed 92% of the BOD, 89% of the COD and 99% of the ammonium nitrogen. Both systems do not experience severe problems dealing with the lack of influent for a duration of seven days. The effluent concentrations did not change much, except for a small peak of nitrite which was present in all tests. However, both the ammonium oxidizing and the nitrite oxidizing bacterial populations were still active, as evidenced by the continued removal of ammonium and formation of nitrate.