TY - JOUR A1 - Miller, Stefan A1 - Schuler, Benjamin A1 - Seckler, Robert T1 - A reversibly unfolding fragment of P22 tailspike protein with native structure : the isolated beta-helix domain Y1 - 1998 ER - TY - JOUR A1 - Schuler, Benjamin A1 - Rachel, Reinhard A1 - Seckler, Robert T1 - Formation of fibrous aggregates from a non-native intermediate : the isolated P22 tailspike -helix domain Y1 - 1999 ER - TY - JOUR A1 - Hoffmann, Armin S. A1 - Kane, Avinash S. A1 - Nettels, Daniel A1 - Hertzog, David E. A1 - Baumgärtel, Peter A1 - Lengefeld, Jan A1 - Reichardt, Gerd A1 - Horsley, David A. A1 - Seckler, Robert A1 - Bakajin, Olgica A1 - Schuler, Benjamin T1 - Mapping protein collapse with single molecule fluorescence and kinetic synchrotron radiation circular dichroism spectroscopy Y1 - 2007 UR - http://www.mendeley.com/research/mapping-protein-collapse-with-singlemolecule-fluorescence-and-kinetic- synchrotron-radiation-circular-dichroism-spectroscopy/# SN - 0027-8424 ER - TY - JOUR A1 - Kane, Avinash S. A1 - Hoffmann, Armin S. A1 - Baumgärtel, Peter A1 - Seckler, Robert A1 - Reichardt, Gerd A1 - Horsley, David A. A1 - Schuler, Benjamin A1 - Bakajin, Olgica T1 - Microfluidic mixers for the investigation of rapid protein folding kinetics using synchrotron radiation circular dichroism spectroscopy N2 - We have developed a microfluidic mixer optimized for rapid measurements of protein folding kinetics using synchrotron radiation circular dichroism (SRCD) spectroscopy. The combination of fabrication in fused silica and synchrotron radiation allows measurements at wavelengths below 220 nm, the typical limit of commercial instrumentation. At these wavelengths, the discrimination between the different types of protein secondary structure increases sharply. The device was optimized for rapid mixing at moderate sample consumption by employing a serpentine channel design, resulting in a dead time of less than 200 ;s. Here, we discuss the design and fabrication of the mixer and quantify the mixing efficiency using wide-field and confocal epi-fluorescence microscopy. We demonstrate the performance of the device in SRCD measurements of the folding kinetics of cytochrome c, a small, fast-folding protein. Our results show that the combination of SRCD with microfluidic mixing opens new possibilities for investigating rapid conformational changes in biological macromolecules that have previously been inaccessible. Y1 - 2008 UR - http://pubs.acs.org/doi/abs/10.1021/ac801764r SN - 0003-2700 ER - TY - JOUR A1 - Schuler, Benjamin A1 - Seckler, Robert T1 - P22 tailspike folding mutants revisited : effects on thermodynamic stability of the isolated beta-helix domain Y1 - 1998 ER - TY - JOUR A1 - Miller, Stefan A1 - Schuler, Benjamin A1 - Seckler, Robert T1 - Phages P22 tailspike protein: Removal of head-binding domain unmasks efects of folding mutations on native- state thermal stability Y1 - 1998 ER - TY - JOUR A1 - Schuler, Benjamin A1 - Fürst, Frank A1 - Osterroth, Frank A1 - Steinbacher, Stefan A1 - Huber, Robert A1 - Seckler, Robert T1 - Plasticity and steric strain in a parallel beta-helix: Rational mutations in P22 tailspike protein N2 - By means of genetic screens, a great number of mutations that affect the folding and stability of the tailspike protein from Salmonella phage P22 have been identified. Temperature-sensitive folding (tsf) mutations decrease folding yields at high temperature, but hardly affect thermal stability of the native trimeric structure when assembled at low temperature. Global suppressor (su) mutations mitigate this phenotype. Virtually all of these mutations are located in the central domain of tailspike, a large parallel beta-helix. We modified tailspike by rational single amino acid replacements at three sites in order to investigate the influence of mutations of two types: (1) mutations expected to cause a tsf phenotype by increasing the side-chain volume of a core residue, and (2) mutations in a similar structural context as two of the four known su mutations, which have been suggested to stabilize folding intermediates and the native structure by the release of backbone strain, an effect well known for residues that are primarily evolved for function and not for stability or folding of the protein. Analysis of folding yields, refolding kinetics and thermal denaturation kinetics in vitro show that the tsf phenotype can indeed be produced rationally by increasing the volume of side chains in the beta-helix core. The high-resolution crystal structure of mutant T326F proves that structural rearrangements only take place in the remarkably plastic lumen of the beta-helix, leaving the arrangement of the hydrogen-bonded backbone and thus the surface of the protein unaffected. This supports the notion that changes in the stability of an intermediate, in which the beta-helix domain is largely formed, are the essential mechanism by which tsf mutations affect tailspike folding. A rational design of su mutants, on the other hand, appears to be more difficult. The exchange of two residues in the active site expected to lead to a drastic release of steric strain neither enhanced the folding properties nor the stability of tailspike. Apparently, side-chain interactions in these cases overcompensate for backbone strain, illustrating the extreme optimization of the tailspike protein for conformational stability. The result exemplifies the view arising from the statistical analysis of the distribution of backbone dihedral angles in known three-dimensional protein structures that the adoption of straight phi/psi angles other than the most favorable ones is often caused by side-chain interactions. Y1 - 2000 UR - http://www3.interscience.wiley.com/cgi-bin/abstract/71001984/START ER -