@article{BaxaWeintraubSeckler2020,
  author    = {Baxa, Ulrich and Weintraub, Andrej and Seckler, Robert},
  title     = {Self-competitive inhibition of the bacteriophage P22 Tailspike endorhamnosidase by O-antigen oligosaccharides},
  series = {Biochemistry},
  volume    = {59},
  journal   = {Biochemistry},
  number    = {51},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0006-2960},
  doi       = {10.1021/acs.biochem.0c00872},
  pages     = {4845 -- 4855},
  year      = {2020},
  abstract  = {The P22 tailspike endorhamnosidase confers the high specificity of bacteriophage P22 for some serogroups of Salmonella differing only slightly in their O-antigen polysaccharide. We used several biophysical methods to study the binding and hydrolysis of O-antigen fragments of different lengths by P22 tailspike protein. O-Antigen saccharides of defined length labeled with fluorophors could be purified with higher resolution than previously possible. Small amounts of naturally occurring variations of 0antigen fragments missing the nonreducing terminal galactose could be used to determine the contribution of this part to the free energy of binding to be similar to 7 kJ/mol. We were able to show via several independent lines of evidence that an unproductive binding mode is highly favored in binding over all other possible binding modes leading to hydrolysis. This is true even under circumstances under which the O-antigen fragment is long enough to be cleaved efficiently by the enzyme. The high-affinity unproductive binding mode results in a strong self-competitive inhibition in addition to product inhibition observed for this system. Self-competitive inhibition is observed for all substrates that have a free reducing end rhamnose. Naturally occurring O-antigen, while still attached to the bacterial outer membrane, does not have a free reducing end and therefore does not perform self-competitive inhibition.},
  language  = {en}
}
@article{WolffSchuelerGastetal.2020,
  author    = {Wolff, Martin and Sch{\"u}ler, Anja and Gast, Klaus and Seckler, Robert and Evers, Andreas and Pfeiffer-Marek, Stefania and Kurz, Michael and Nagel, Norbert and Haack, Torsten and Wagner, Michael and Thalhammer, Anja},
  title     = {Self-Assembly of Exendin-4-Derived Dual Peptide Agonists is Mediated by Acylation and Correlated to the Length of Conjugated Fatty Acyl Chains},
  series = {Molecular pharmaceutics},
  volume    = {17},
  journal   = {Molecular pharmaceutics},
  number    = {3},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1543-8384},
  doi       = {10.1021/acs.molpharmaceut.9b01195},
  pages     = {965 -- 978},
  year      = {2020},
  abstract  = {Dual glucagon-like peptide-1/glucagon receptor agonists have emerged as promising candidates for the treatment of diabetes and obesity. Issues of degradation sensitivity and rapid renal clearance are addressed, for example, by the conjugation of peptides to fatty acid chains, promoting reversible albumin binding. We use combined dynamic and static light scattering to directly measure the self-assembly of a set of dual peptide agonists based on the exendin-4 structure with varying fatty acid chain lengths in terms of apparent molecular mass and hydrodynamic radius (R-S). We use NMR spectroscopy to gain an insight into the molecular architecture of the assembly. We investigate conformational changes of the monomeric subunits resulting from peptide self-assembly and assembly stability as a function of the fatty acid chain length using circular dichroism and fluorescence spectroscopy. Our results demonstrate that self-assembly of the exendin-4-derived dual agonist peptides is essentially driven by hydrophobic interactions involving the conjugated acyl chains. The fatty acid chain length affects assembly equilibria and the assembly stability, although the peptide subunits in the assembly retain a dynamic secondary structure. The assembly architecture is characterized by juxtaposition of the fatty acyl side chains and a hydrophobic cluster of the peptide moiety. This cluster experiences local conformational changes in the assembly compared to the monomeric unit leading to a reduction in solvent exposure. The N-terminal half of the peptide and a C-terminal loop are not in contact with neighboring peptide subunits in the assemblies. Altogether, our study contributes to a thorough understanding of the association characteristics and the tendency toward self-assembly in response to lipidation. This is important not only to achieve the desired bioavailability but also with respect to the physical stability of peptide solutions.},
  language  = {en}
}
@article{WolffGastEversetal.2021,
  author    = {Wolff, Martin and Gast, Klaus and Evers, Andreas and Kurz, Michael and Pfeiffer-Marek, Stefania and Sch{\"u}ler, Anja and Seckler, Robert and Thalhammer, Anja},
  title     = {A Conserved Hydrophobic Moiety and Helix-Helix Interactions Drive the Self-Assembly of the Incretin Analog Exendin-4},
  series = {Biomolecules},
  volume    = {11},
  journal   = {Biomolecules},
  number    = {9},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2218-273X},
  doi       = {10.3390/biom11091305},
  pages     = {20},
  year      = {2021},
  abstract  = {Exendin-4 is a pharmaceutical peptide used in the control of insulin secretion. Structural information on exendin-4 and related peptides especially on the level of quaternary structure is scarce. We present the first published association equilibria of exendin-4 directly measured by static and dynamic light scattering. We show that exendin-4 oligomerization is pH dependent and that these oligomers are of low compactness. We relate our experimental results to a structural hypothesis to describe molecular details of exendin-4 oligomers. Discussion of the validity of this hypothesis is based on NMR, circular dichroism and fluorescence spectroscopy, and light scattering data on exendin-4 and a set of exendin-4 derived peptides. The essential forces driving oligomerization of exendin-4 are helix-helix interactions and interactions of a conserved hydrophobic moiety. Our structural hypothesis suggests that key interactions of exendin-4 monomers in the experimentally supported trimer take place between a defined helical segment and a hydrophobic triangle constituted by the Phe22 residues of the three monomeric subunits. Our data rationalize that Val19 might function as an anchor in the N-terminus of the interacting helix-region and that Trp25 is partially shielded in the oligomer by C-terminal amino acids of the same monomer. Our structural hypothesis suggests that the Trp25 residues do not interact with each other, but with C-terminal Pro residues of their own monomers.},
  language  = {en}
}
@misc{WolffGastEversetal.2021,
  author    = {Wolff, Martin and Gast, Klaus and Evers, Andreas and Kurz, Michael and Pfeiffer-Marek, Stefania and Sch{\"u}ler, Anja and Seckler, Robert and Thalhammer, Anja},
  title     = {A Conserved Hydrophobic Moiety and Helix-Helix Interactions Drive the Self-Assembly of the Incretin Analog Exendin-4},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {9},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-52208},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-522081},
  pages     = {22},
  year      = {2021},
  abstract  = {Exendin-4 is a pharmaceutical peptide used in the control of insulin secretion. Structural information on exendin-4 and related peptides especially on the level of quaternary structure is scarce. We present the first published association equilibria of exendin-4 directly measured by static and dynamic light scattering. We show that exendin-4 oligomerization is pH dependent and that these oligomers are of low compactness. We relate our experimental results to a structural hypothesis to describe molecular details of exendin-4 oligomers. Discussion of the validity of this hypothesis is based on NMR, circular dichroism and fluorescence spectroscopy, and light scattering data on exendin-4 and a set of exendin-4 derived peptides. The essential forces driving oligomerization of exendin-4 are helix-helix interactions and interactions of a conserved hydrophobic moiety. Our structural hypothesis suggests that key interactions of exendin-4 monomers in the experimentally supported trimer take place between a defined helical segment and a hydrophobic triangle constituted by the Phe22 residues of the three monomeric subunits. Our data rationalize that Val19 might function as an anchor in the N-terminus of the interacting helix-region and that Trp25 is partially shielded in the oligomer by C-terminal amino acids of the same monomer. Our structural hypothesis suggests that the Trp25 residues do not interact with each other, but with C-terminal Pro residues of their own monomers.},
  language  = {en}
}
@article{WolffSchuelerGastetal.2020,
  author    = {Wolff, Martin and Sch{\"u}ler, Anja and Gast, Klaus and Seckler, Robert and Evers, Andreas and Pfeiffer-Marek, Stefania and Kurz, Michael and Nagel, Norbert and Haack, Torsten and Wagner, Michael and Thalhammer, Anja},
  title     = {Self-Assembly of Exendin-4-Derived Dual Peptide Agonists is Mediated by Acylation and Correlated to the Length of Conjugated Fatty Acyl Chains},
  series = {Molecular pharmaceutics},
  volume    = {17},
  journal   = {Molecular pharmaceutics},
  number    = {3},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1543-8384},
  doi       = {10.1021/acs.molpharmaceut.9b01195},
  pages     = {965 -- 978},
  year      = {2020},
  abstract  = {Dual glucagon-like peptide-1/glucagon receptor agonists have emerged as promising candidates for the treatment of diabetes and obesity. Issues of degradation sensitivity and rapid renal clearance are addressed, for example, by the conjugation of peptides to fatty acid chains, promoting reversible albumin binding. We use combined dynamic and static light scattering to directly measure the self-assembly of a set of dual peptide agonists based on the exendin-4 structure with varying fatty acid chain lengths in terms of apparent molecular mass and hydrodynamic radius (R-S). We use NMR spectroscopy to gain an insight into the molecular architecture of the assembly. We investigate conformational changes of the monomeric subunits resulting from peptide self-assembly and assembly stability as a function of the fatty acid chain length using circular dichroism and fluorescence spectroscopy. Our results demonstrate that self-assembly of the exendin-4-derived dual agonist peptides is essentially driven by hydrophobic interactions involving the conjugated acyl chains. The fatty acid chain length affects assembly equilibria and the assembly stability, although the peptide subunits in the assembly retain a dynamic secondary structure. The assembly architecture is characterized by juxtaposition of the fatty acyl side chains and a hydrophobic cluster of the peptide moiety. This cluster experiences local conformational changes in the assembly compared to the monomeric unit leading to a reduction in solvent exposure. The N-terminal half of the peptide and a C-terminal loop are not in contact with neighboring peptide subunits in the assemblies. Altogether, our study contributes to a thorough understanding of the association characteristics and the tendency toward self-assembly in response to lipidation. This is important not only to achieve the desired bioavailability but also with respect to the physical stability of peptide solutions.},
  language  = {en}
}
@article{GastSchuelerWolffetal.2017,
  author    = {Gast, Klaus and Sch{\"u}ler, Anja and Wolff, Martin and Thalhammer, Anja and Berchtold, Harald and Nagel, Norbert and Lenherr, Gudrun and Hauck, Gerrit and Seckler, Robert},
  title     = {Rapid-acting and human insulins},
  series = {Pharmaceutical research},
  volume    = {34},
  journal   = {Pharmaceutical research},
  number    = {795},
  publisher = {Springer},
  address   = {New York},
  issn      = {0724-8741},
  doi       = {10.1007/s11095-017-2233-0},
  pages     = {2270 -- 2286},
  year      = {2017},
  abstract  = {Comparison of the dissociation kinetics of rapid-acting insulins lispro, aspart, glulisine and human insulin under physiologically relevant conditions. Dissociation kinetics after dilution were monitored directly in terms of the average molecular mass using combined static and dynamic light scattering. Changes in tertiary structure were detected by near-UV circular dichroism. Glulisine forms compact hexamers in formulation even in the absence of Zn2+. Upon severe dilution, these rapidly dissociate into monomers in less than 10 s. In contrast, in formulations of lispro and aspart, the presence of Zn2+ and phenolic compounds is essential for formation of compact R6 hexamers. These slowly dissociate in times ranging from seconds to one hour depending on the concentration of phenolic additives. The disadvantage of the long dissociation times of lispro and aspart can be diminished by a rapid depletion of the concentration of phenolic additives independent of the insulin dilution. This is especially important in conditions similar to those after subcutaneous injection, where only minor dilution of the insulins occurs. Knowledge of the diverging dissociation mechanisms of lispro and aspart compared to glulisine will be helpful for optimizing formulation conditions of rapid-acting insulins.},
  language  = {en}
}
@misc{SchmidtEckardtMarszałeketal.2014,
  author    = {Schmidt, Anna and Eckardt, Barbara and Marszałek, Magdalena and G{\"o}rlich, Petra and Bieber, Sabine and Kampe, Heike and J{\"a}ger, Sophie and Horn-Conrad, Antje and G{\"u}nther, Oliver and Seckler, Robert and Sepp{\"a}, Silvana and Guske, Katja and Szameitat, Ulrike and Bezzenberger, Tilman and S{\"u}tterlin, Sabine and Weller, Nina and Klauke, Lars},
  title     = {Portal = Sommer an der Uni: Leere H{\"o}rs{\"a}le? Volle Terminkalender!},
  number    = {03/2014},
  organization    = {Universit{\"a}t Potsdam, Referat f{\"u}r Presse- und {\"O}ffentlichkeitsarbeit},
  doi       = {10.25932/publishup-44302},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-443021},
  pages     = {42},
  year      = {2014},
  abstract  = {Aus dem Inhalt: - Sommer an der Uni: Leere H{\"o}rs{\"a}le? Volle Terminkalender! - St{\"a}rken st{\"a}rken - Unter Stress},
  language  = {de}
}
@misc{GastSchuelerWolffetal.2017,
  author    = {Gast, Klaus and Sch{\"u}ler, Anja and Wolff, Martin and Thalhammer, Anja and Berchtold, Harald and Nagel, Norbert and Lenherr, Gudrun and Hauck, Gerrit and Seckler, Robert},
  title     = {Rapid-acting and human insulins},
  series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe},
  number    = {795},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-43157},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-431572},
  pages     = {2270 -- 2286},
  year      = {2017},
  abstract  = {Purpose: Comparison of the dissociation kinetics of rapid-acting insulins lispro, aspart, glulisine and human insulin under physiologically relevant conditions. Methods: Dissociation kinetics after dilution were monitored directly in terms of the average molecular mass using combined static and dynamic light scattering. Changes in tertiary structure were detected by near-UV circular dichroism. Results: Glulisine forms compact hexamers in formulation even in the absence of Zn2+. Upon severe dilution, these rapidly dissociate into monomers in less than 10 s. In contrast, in formulations of lispro and aspart, the presence of Zn2+ and phenolic compounds is essential for formation of compact R6 hexamers. These slowly dissociate in times ranging from seconds to one hour depending on the concentration of phenolic additives. The disadvantage of the long dissociation times of lispro and aspart can be diminished by a rapid depletion of the concentration of phenolic additives independent of the insulin dilution. This is especially important in conditions similar to those after subcutaneous injection, where only minor dilution of the insulins occurs. Conclusion: Knowledge of the diverging dissociation mechanisms of lispro and aspart compared to glulisine will be helpful for optimizing formulation conditions of rapid-acting insulins.},
  language  = {en}
}
@misc{GraefSecklerHagemannetal.2012,
  author    = {Gr{\"a}f, Ralph and Seckler, Robert and Hagemann, Alfred and D'Aprile, Iwan-Michelangelo and Schulte, Christoph and Zimmermann, Matthias and Blom, Hans and Horn-Conrad, Antje and Kampe, Heike and J{\"a}ger, Sophie and Haase, Jana and Eckardt, Barbara and Priebs-Tr{\"o}ger, Astrid and Walz, Bernd},
  title     = {Portal Wissen = Raum},
  number    = {01/2012},
  organization    = {Universit{\"a}t Potsdam, Referat f{\"u}r Presse- und {\"O}ffentlichkeitsarbeit},
  issn      = {2194-4237},
  doi       = {10.25932/publishup-44078},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-440785},
  pages     = {98},
  year      = {2012},
  abstract  = {Mit „Portal Wissen" laden wir Sie ein, die Forschung an der Universit{\"a}t Potsdam zu entdecken und in ihrer Vielfalt kennenzulernen. In der ersten Ausgabe dreht sich alles um „R{\"a}ume". R{\"a}ume, in denen geforscht wird, solche, die es zu erforschen gilt, andere, die durch Wissenschaft zug{\"a}nglich oder erschlossen werden, aber auch R{\"a}ume, die Wissenschaft braucht, um sich entfalten zu k{\"o}nnen. Forschung vermisst R{\"a}ume: „Wissenschaft wird von Menschen gemacht", schrieb der Physiker Werner Heisenberg. Umgekehrt l{\"a}sst sich sagen: Wissenschaft macht Menschen, widmet sich ihnen, beeinflusst sie. Dieser Beziehung ist „Portal Wissen" nachgegangen. Wir haben Wissenschaftler getroffen, sie gefragt, wie aus ihren Fragen Projekte entstehen, haben sie auf dem oft verschlungenen Weg zum Ziel begleitet. Ein besonderes Augenmerk dieses Heftes gilt den „Kulturellen Begegnungsr{\"a}umen", denen ein eigener Profilbereich der Forschung an der Universit{\"a}t Potsdam gewidmet ist. Forschung hat R{\"a}ume: Labore, Bibliotheken, Gew{\"a}chsh{\"a}user oder Archive - hier ist Wissenschaft zu Liebe Leserinnen und Leser, Hause. All diese Orte sind so einzigartig wie die Wissenschaftler, die in ihnen arbeiten, oder die Untersuchungen, die hier stattfinden. Erst die Vision davon, wie ein Problem zu l{\"o}sen ist, macht aus einfachen Zimmern „Laborr{\"a}ume". Wir haben ihre T{\"u}ren ge{\"o}ffnet, um zu zeigen, was - und wer - sich dahinter befindet. Forschung er{\"o}ffnet R{\"a}ume: Wenn Wissenschaft erfolgreich ist, bewegt sie uns, bringt uns voran. Auf dem Weg einer wissenschaftlichen Erkenntnis aus dem Labor in den Alltag stehen mitunter H{\"u}rden, die meist nicht auf den ersten Blick zu erkennen sind. Auf jeden Fall aber ist ihre Anwendung erster Ausgangspunkt von Wissenschaft, Antrieb und Motivation jedes Forschers. „Portal Wissen" zeigt, welche „Praxisr{\"a}ume" sich aus der {\"U}bersetzung von Forschungsresultaten ergeben. Dort, wo wir es unbedingt erwarten, und dort, wo vielleicht nicht. Forschung erschließt R{\"a}ume: Bei Expeditionen, Feldversuchen und Exkursionen wird nahezu jede Umgebung zum mobilen Labor. So er{\"o}ffnet Wissenschaft Zug{\"a}nge auch zu Orten, die auf vielfach andere Weise verschlossen oder unzug{\"a}nglich scheinen. Wir haben uns in Forscher- Reisetaschen gemogelt, um bei Entdeckungsreisen dabei zu sein, die weit weg - vor allem nach Afrika - f{\"u}hren. Zugleich haben wir beobachtet, wie „Entwicklungsr{\"a}ume" sich auch von Potsdam aus erschließen lassen oder zumindest ihre Vermessung in Potsdam beginnen kann. Forschung braucht R{\"a}ume: Wissenschaft hat zwei Geschlechter, endlich. Noch nie waren so viele Frauen in der Forschung t{\"a}tig wie derzeit. Ein Grund zum Ausruhen ist dies gleichwohl nicht. Deutschlandweit ist aktuell nur jede f{\"u}nfte Professur von einer Frau besetzt. „Portal Wissen" schaut, welche „Entwicklungsr{\"a}ume" Frauen sich in der Wissenschaft, aber auch dar{\"u}ber hinaus geschaffen haben. Und wo sie ihnen verwehrt werden. Wir w{\"u}nschen Ihnen eine anregende Lekt{\"u}re und dass auch Sie einen Raum finden, der Sie inspiriert. Prof. Dr. Robert Seckler Vizepr{\"a}sident f{\"u}r Forschung und wissenschaftlichen Nachwuchs},
  language  = {de}
}
@article{SeulMuellerAndresetal.2014,
  author    = {Seul, Anait and M{\"u}ller, J{\"u}rgen J. and Andres, Dorothee and Stettner, Eva and Heinemann, Udo and Seckler, Robert},
  title     = {Bacteriophage P22 tailspike: structure of the complete protein and function of the interdomain linker},
  series = {Acta crystallographica : Section D, Biological crystallography},
  volume    = {70},
  journal   = {Acta crystallographica : Section D, Biological crystallography},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {1399-0047},
  doi       = {10.1107/S1399004714002685},
  pages     = {1336 -- 1345},
  year      = {2014},
  abstract  = {Attachment of phages to host cells, followed by phage DNA ejection, represents the first stage of viral infection of bacteria. Salmonella phage P22 has been extensively studied, serving as an experimental model for bacterial infection by phages. P22 engages bacteria by binding to the sugar moiety of lipopolysaccharides using the viral tailspike protein for attachment. While the structures of the N-terminal particle-binding domain and the major receptor-binding domain of the tailspike have been analyzed individually, the three-dimensional organization of the intact protein, including the highly conserved linker region between the two domains, remained unknown. A single amino-acid exchange in the linker sequence made it possible to crystallize the full-length protein. Two crystal structures of the linker region are presented: one attached to the N-terminal domain and the other present within the complete tailspike protein. Both retain their biological function, but the mutated full-length tailspike displays a retarded folding pathway. Fitting of the full-length tailspike into a published cryo-electron microscopy map of the P22 virion requires an elastic distortion of the crystal structure. The conservation of the linker suggests a role in signal transmission from the distal tip of the molecule to the phage head, eventually leading to DNA ejection.},
  language  = {en}
}