Modeling,Analysis, and Simulation of Biofilm Formation and Decay

In this article, we give a brief overview of our recent work on continuum mechanical modelling and simulation of microbial films. This comprises some classical tasks of applied mathematics such as computational fluid dynamics, analysis of partial differential equations, and mathematical biology.     

Ein Verfahren zur' gleichzeitigen Erkennung und Bestimmung der schwefligen S?ure in einem Arbeitsgange

Ohne Zusammenfassung     

Conformational Dynamics of Sensory Rhodopsin II in Nanolipoprotein and Styrene–Maleic Acid Lipid Particles

Styrene–maleic acid lipid particles (SMALPs) provide stable water‐soluble nanocontainers for lipid‐encased membrane proteins. Possible effects of the SMA‐stabilized lipid environment on the interaction dynamics between functionally coupled membrane proteins remain to be elucidated. The photoreceptor sensory rhodopsin II, NpSRII and its cognate transducer, NpHtrII, of Natronomonas pharaonis form a transmembrane complex, NpSRII₂/NpHtrII₂ that plays a key role in negative phototaxis and provides a unique model system to study the light‐induced transfer of a conformational signal between two integral membrane proteins. Photon absorption induces transient structural changes in NpSRII comprising an outward movement of helix F that cause further conformational alterations in NpHtrII. We applied site‐directed spin labeling and time‐resolved optical and EPR spectroscopy to compare the conformational dynamics of NpSRII₂/NpHtrII₂ reconstituted in SMALPs with that of nanolipoprotein particle and liposome preparations. NpSRII and NpSRII₂/NpHtrII₂ show similar photocycles in liposomes and nanolipoprotein particles. An accelerated decay of the M photointermediate found for SMALPs can be explained by a high local proton concentration provided by the carboxylic groups of the SMA polymer. Light‐induced large‐scale conformational changes of NpSRII₂/NpHtrII₂ observed in liposomes and nanolipoprotein particles are affected in SMALPs, indicating restrictions of the protein's conformational freedom.     

Site‐Directed Spin‐Labeling of DNA by the Azide–Alkyne ‘Click’ Reaction: Nanometer Distance Measurements on 7‐Deaza‐2′‐deoxyadenosine and 2′‐Deoxyuridine Nitroxide Conjugates Spatially Separated or Linked to a ‘dA‐dT’ Base Pair

Nucleobase‐directed spin‐labeling by the azide‐alkyne ‘click’ (CuAAC) reaction has been performed for the first time with oligonucleotides. 7‐Deaza‐7‐ethynyl‐2′‐deoxyadenosine ( 1 ) and 5‐ethynyl‐2′‐deoxyuridine ( 2 ) were chosen to incorporate terminal triple bonds into DNA. Oligonucleotides containing 1 or 2 were synthesized on a solid phase and spin labeling with 4‐azido‐2,2,6,6‐tetramethylpiperidine 1‐oxyl (4‐azido‐TEMPO, 3 ) was performed by post‐modification in solution. Two spin labels ( 3 ) were incorporated with high efficiency into the DNA duplex at spatially separated positions or into a ‘dA‐dT’ base pair. Modification at the 5‐position of the pyrimidine base or at the 7‐position of the 7‐deazapurine residue gave steric freedom to the spin label in the major groove of duplex DNA. By applying cw and pulse EPR spectroscopy, very accurate distances between spin labels, within the range of 1–2 nm, were measured. The spin–spin distance was 1.8±0.2 nm for DNA duplex 17 ( dA*^7,10 ) ?11 containing two spin labels that are separated by two nucleotides within one individual strand. A distance of 1.4±0.2 nm was found for the spin‐labeled ‘dA‐dT’ base pair 15 ( dA*⁷ ) ?16 ( dT*⁶ ). The ‘click’ approach has the potential to be applied to all four constituents of DNA, which indicates the universal applicability of the method. New insights into the structural changes of canonical or modified DNA are expected to provide additional information on novel DNA structures, protein interaction, DNA architecture, and synthetic biology.     

Untersuchung von Mehl, Brot, Teigwaren

Ohne Zusammenfassung