@article{VillatoroZuehlkeRiebeetal., author = {Villatoro, Jos{\´e} and Z{\"u}hlke, Martin and Riebe, Daniel and Beitz, Toralf and Weber, Marcus and Riedel, Jens and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {IR-MALDI ion mobility spectrometry: physical source characterization and application as HPLC detector}, series = {International Journal for Ion Mobility Spectrometry}, journal = {International Journal for Ion Mobility Spectrometry}, number = {19/4}, doi = {10.1007/s12127-016-0208-1}, pages = {197 -- 297}, language = {en} } @article{VillatoroZuehlkeRiebeetal., author = {Villatoro, Jose and Z{\"u}hlke, Martin and Riebe, Daniel and Riedel, Jens and Beitz, Toralf and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {IR-MALDI ion mobility spectrometry}, series = {Analytical and Bioanalytical Chemistry}, volume = {408}, journal = {Analytical and Bioanalytical Chemistry}, number = {23}, doi = {10.1007/s00216-016-9739-x}, pages = {6259 -- 6268}, language = {en} } @article{SchradeTroegerEldashanetal., author = {Schrade, Katharina and Tr{\"o}ger, Jessica and Eldashan, Adeep and Z{\"u}hlke, Kerstin and Abdul Azees, Kamal R. and Elkins, Jonathan M. and Neuenschwander, Martin and Oder, Andreas and Elkewedi, Mohamed and Jaksch, Sarah and Andrae, Karsten and Li, Jinliang and Fernandes, Jaoa and M{\"u}ller, Paul Markus and Grunwald, Stephan and Marino, Stephen F. and Vukicevic, Tanja and Eichhorst, Jenny and Wiesner, Burkhard and Weber, Marcus and Kapiloff, Michael and Rocks, Oliver and Daumke, Oliver and Wieland, Thomas and Knapp, Stefan and von Kries, Jens Peter and Klussmann, Enno}, title = {An AKAP-Lbc-RhoA interaction inhibitor promotes the translocation of aquaporin-2 to the plasma membrane of renal collecting duct principal cells}, series = {PLOS ONE}, volume = {13}, journal = {PLOS ONE}, number = {1}, doi = {10.1371/journal.pone.0191423}, pages = {e0191423 -- e0191423}, abstract = {Stimulation of renal collecting duct principal cells with antidiuretic hormone (arginine-vasopressin, AVP) results in inhibition of the small GTPase RhoA and the enrichment of the water channel aquaporin-2 (AQP2) in the plasma membrane. The membrane insertion facilitates water reabsorption from primary urine and fine-tuning of body water homeostasis. Rho guanine nucleotide exchange factors (GEFs) interact with RhoA, catalyze the exchange of GDP for GTP and thereby activate the GTPase. However, GEFs involved in the control of AQP2 in renal principal cells are unknown. The A-kinase anchoring protein, AKAP-Lbc, possesses GEF activity, specifically activates RhoA, and is expressed in primary renal inner medullary collecting duct principal (IMCD) cells. Through screening of 18,431 small molecules and synthesis of a focused library around one of the hits, we identified an inhibitor of the interaction of AKAP-Lbc and RhoA. This molecule, Scaff10-8, bound to RhoA, inhibited the AKAP-Lbc-mediated RhoA activation but did not interfere with RhoA activation through other GEFs or activities of other members of the Rho family of small GTPases, Rac1 and Cdc42. Scaff10-8 promoted the redistribution of AQP2 from intracellular vesicles to the periphery of IMCD cells. Thus, our data demonstrate an involvement of AKAP-Lbc-mediated RhoA activation in the control of AQP2 trafficking.}, language = {en} } @article{VillatoroZuehlkeRiebeetal., author = {Villatoro, Jos{\´e} and Z{\"u}hlke, Martin and Riebe, Daniel and Beitz, Toralf and Weber, Marcus and L{\"o}hmannsr{\"o}ben, Hans-Gerd}, title = {Sub-ambient pressure IR-MALDI ion mobility spectrometer for the determination of low and high field mobilities}, series = {Analytical and Bioanalytical Chemistry}, volume = {412}, journal = {Analytical and Bioanalytical Chemistry}, doi = {10.1007/s00216-020-02735-0}, pages = {5247 -- 5260}, abstract = {A new ion mobility (IM) spectrometer, enabling mobility measurements in the pressure range between 5 and 500 mbar and in the reduced field strength range E/N of 5-90 Td, was developed and characterized. Reduced mobility (K0) values were studied under low E/N (constant value) as well as high E/N (deviation from low field K0) for a series of molecular ions in nitrogen. Infrared matrix-assisted laser desorption ionization (IR-MALDI) was used in two configurations: a source working at atmospheric pressure (AP) and, for the first time, an IR-MALDI source working with a liquid (aqueous) matrix at sub-ambient/reduced pressure (RP). The influence of RP on IR-MALDI was examined and new insights into the dispersion process were gained. This enabled the optimization of the IM spectrometer for best analytical performance. While ion desolvation is less efficient at RP, the transport of ions is more efficient, leading to intensity enhancement and an increased number of oligomer ions. When deciding between AP and RP IR-MALDI, a trade-off between intensity and resolving power has to be considered. Here, the low field mobility of peptide ions was first measured and compared with reference values from ESI-IM spectrometry (at AP) as well as collision cross sections obtained from molecular dynamics simulations. The second application was the determination of the reduced mobility of various substituted ammonium ions as a function of E/N in nitrogen. The mobility is constant up to a threshold at high E/N. Beyond this threshold, mobility increases were observed. This behavior can be explained by the loss of hydrated water molecules.}, language = {en} } @article{VillatoroWeberZuehlkeetal., author = {Villatoro, Jos{\´e} and Weber, Marcus and Z{\"u}hlke, Martin and Lehmann, Andreas and Zechiowski, Karl and Riebe, Daniel and Beitz, Toralf and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Kreuzer, Oliver}, title = {Structural characterization of synthetic peptides using electronspray ion mobility spectrometry and molecular dynamics simulations}, series = {International Journal of Mass Spectrometry}, volume = {436}, journal = {International Journal of Mass Spectrometry}, doi = {10.1016/j.ijms.2018.10.036}, pages = {108 -- 117}, abstract = {Electrospray ionization-ion mobility spectrometry was employed for the determination of collision cross sections (CCS) of 25 synthetically produced peptides in the mass range between 540-3310 Da. The experimental measurement of the CCS is complemented by their calculation applying two different methods. One prediction method is the intrinsic size parameter (ISP) method developed by the Clemmer group. The second new method is based on the evaluation of molecular dynamics (MD) simulation trajectories as a whole, resulting in a single, averaged collision cross-section value for a given peptide in the gas phase. A high temperature MD simulation is run in order to scan through the whole conformational space. The lower temperature conformational distribution is obtained through thermodynamic reweighting. In the first part, various correlations, e.g. CCS vs. mass and inverse mobility vs. m/z correlations, are presented. Differences in CCS between peptides are also discussed in terms of their respective mass and m/z differences, as well as their respective structures. In the second part, measured and calculated CCS are compared. The agreement between the prediction results and the experimental values is in the same range for both calculation methods. While the calculation effort of the ISP method is much lower, the MD method comprises several tools providing deeper insights into the conformations of peptides. Advantages and limitations of both methods are discussed. Based on the separation of two pairs of linear and cyclic peptides of virtually the same mass, the influence of the structure on the cross sections is discussed. The shift in cross section differences and peak shape after transition from the linear to the cyclic peptide can be well understood by applying different MD tools, e.g. the root-mean-square deviation (RMSD) and the root mean square fluctuation (RMSF).}, language = {en} }