University\u27s 10th Annual Green Week Begins April 17

Campus and community organizations raise awareness of resource stewardshi

Award-Winning Poet, Essayist to Deliver Earth Day Keynote Address

Camille Dungy to close UM Green Week celebration April 2

A versatile Scaffold: The binding specificities of the Par3 PDZ domains mediate multiple interactions with polarity proteins

The asymmetric distribution of RNA, lipids and proteins is the basis of cell polarity. Polarized cells are vital for the organization of multicellular organism. Malfunctions in the processes generating cell polarity are linked with cancer and developmental defects. For cell polarization, the PAR complex, consisting of atypical protein kinase C, Par3 and Par6, is essential. Par3 is the central scaffold of the PAR complex. Par3 comprises of an N-terminal oligomerization domain, three Postsynaptic density protein-95, Disk large, Zonula occludens 1 (PDZ) domains, a kinase binding domain and an unstructured C-terminus. Its PDZ domains are the major protein-protein interaction domains. However, a detailed analysis of their specificities towards PDZ binding motifs (PBMs) occurring in Par3 interaction partners in the environment of cell polarity is missing. Here, I present the structural basis of the interaction of Par3 with Par6. I identified a PBM in Par6 that is essential for Par3 interaction and interacts with the PDZ1 and PDZ3, but not the PDZ2 domains in vitro. Together with my coauthors, I showed that the Par6 PBM interacts with Par3 via a canonical PDZ:PBM interaction and functions together with the Par6 PDZ domain in Par6 localization in vivo. In addition, I investigated the specificities of the individual Par3 PDZ domains for cell polarity proteins. My analysis revealed a unique binding profile for the dmPar3 PDZ1 and PDZ2 domains, while the binding profile of the dmPar3 PDZ3 domain is very promiscuous and overlaps with the specificities of the other two Par3 PDZ domains. These overlapping specificities enable Par3 to mediate multivalent interactions and thereby enable Par3 to form large protein networks with many different cell polarity proteins. In a third project, I discovered a hitherto unknown short motif N-terminal of the third PDZ domain of dmPar3, denoted FID-motif. I was able to show that the FID-motif folds back onto the dmPar3 PDZ3 domain in close vicinity of the PBM binding groove thereby reducing the affinities of the PDZ3 domain towards various PBMs in polarity proteins. These reductions in affinity prevent a subset of the previous identified PDZ3 ligands to interact with the PDZ3 domain. Hence, the FID-motif seems to fine-tune the recruitment of PBM-carrying polarity proteins via the dmPar3 PDZ3 domain. The detailed analyses presented in this thesis provide important insights into the individual roles of the Par3 PDZ domains in the assembly of polarity protein complexes. I present new clues in regard of functional redundancies within the Par3 PDZ module and provide the further evidence for Par3 acting as a central scaffold of polarity protein networks. Therefore, the function of the Par3 protein during establishment, maintenance and disruption of cell polarity during development and the related process of cancer metastasis can be understood in greater detail

Application of the WEPP model with digital geographic information

The Water Erosion Prediction Project (WEPP) is a process-based continuous simulation erosion model that can be applied to hillslope profiles and small watersheds. One limitation to application of WEPP (or other models) to the field or farm scale is the difficulty in determining the watershed structure, which may be composed of multiple channels and profiles (and potentially other features as well). This presentation describes current efforts to link the WEPP model with Geographic Information Systems (GIS) and utilize Digital Elevation Model (DEM) data to generate the necessary topographic inputs for erosion model simulations. Two automated approaches for applying the WEPP model have been developed and compared to manual application of the model. The first approach (named the Hillslope method) uses information from a DEM to delineate the watershed boundary, channel and hillslope locations, and then configure "representative" hillslope slope profiles from the myriad flowpath data. The second approach (named the Flowpath method) also uses DEM information to delineate the watershed boundary, but then runs WEPP model simulations on every flowpath within a watershed. For a set of research watersheds, the automatic Hillslope method performed as well as a manual application of WEPP by an expert user in predictions of runoff and sediment loss. Tests also showed that the Hillslope and Flowpath methods were not significantly different than each other or different from manual model applications in predictions of hillslope erosion. Additional research work ongoing at the National Soil Erosion Research Laboratory is examining the feasibility of using commonly available digital elevation data (for example from on-vehicle Geographical Positioning Systems (GPS)) to provide input for the automated techniques for driving the erosion model

Different approaches to model economic dimension of community resilience

Earthquakes and extreme events in general cause direct and indirect economic effects on every major economic sector of a given community. These effects have grown in the last years due to the increasing interdependency of the infrastructures and make the community more vulnerable to natural and human-induced disruptive events. Therefore, there is need for metrics and models which are able to describe economic resilience, defined as the ability of a community affected by a disaster to resist at the shock and bounce back to the economy in normal operating conditions. Several attempts have been made in the past to achieve a better measurement and representation of the economic resilience and to find suitable metrics to help decision planning. The most popular methodologies are based on Computable General Equilibrium models (CGE) and Inoperability Input-Output models (IIM). In this study, we analyze these methods, showing advantages and limitations. Finally, a new method is proposed to evaluate economic resilience which is based on equilibrium growth models and compared with other approaches

Characterization of Hamamatsu 64-channel TSV SiPMs

The Hamamatsu UV-light enhanced 64-channel SiPM array of the newest generation (S13361-3050AS-08) has been examined for the purpose of being used for the Silicon Elementary Cell Add-on (SiECA) of the EUSO-SPB balloon experiment. Characterization measurements have been performed with the newly installed Single Photon Calibration Stand at KIT (SPOCK). The results of the characterization measurements including the breakdown voltage, the gain, the PDE, the dark-count rate and the crosstalk probability of all 64 SiPM channels are presented. Additional measurements of the SiPM sensitivity to photons with wavelengths lower than 400nm show an improved PDE for small wavelengths compared to the SiPM array S12642-0808PA-50, which was also investigated for comparison. The response dynamics have been investigated for low numbers of incoming photons. Temperature dependent measurements of the gain, the PDE, the dark-count rate and the crosstalk probability have been performed for one channel of the SiPM array.Comment: Accepted for publication in Nuclear Instruments and Methods