NMR Study of Rcf2 Reveals an Unusual Dimeric Topology in Detergent Micelles

The Saccharomyces cerevisiae mitochondrial respiratory supercomplex factor 2 (Rcf2) plays a role in assembly of supercomplexes composed of cytochrome bc₁ (complex III ) and cytochrome c oxidase (complex IV ). We expressed the Rcf2 protein in Escherichia coli, refolded it, and reconstituted it into dodecylphosphocholine (DPC) micelles. The structural properties of Rcf2 were studied by solution NMR, and near complete backbone assignment of Rcf2 was achieved. The secondary structure of Rcf2 contains seven helices, of which five are putative transmembrane (TM) helices, including, unexpectedly, a region formed by a charged 20‐residue helix at the C terminus. Further studies demonstrated that Rcf2 forms a dimer, and the charged TM helix is involved in this dimer formation. Our results provide a basis for understanding the role of this assembly/regulatory factor in supercomplex formation and function.     

Dynamics of the KB Proton Pathway in Cytochrome ba3 from Thermus thermophilus

The ba₃ cytochrome c oxidase from Thermus thermophilus is a B-type oxygen-reducing heme-copper oxidase and a proton pump. It uses only one proton pathway for transfer of protons to the catalytic site, the K^B pathway. It was previously shown that the ba₃ oxidase has an overall similar reaction sequence to that in mitochondrial-like A-type oxidases. However, the timing of loading the pump site, and formation and decay of catalytic intermediates is different in the two types of oxidases. In the present study, we have investigated variants in which two amino acids of the K^B proton pathway leading to the catalytic site were exchanged; Tyr-248 (located ∼23 Å below the active site towards the cytoplasm) in subunit I (Y248T) and Glu-15 (∼26 Å below the active site, ∼16 Å from Tyr-248) in subunit II (E15^IIQ). Even though the overall catalytic turnover in these two variants is similar and very low (<1 % of wildtype), the substitutions had distinctly different effects on the kinetics of proton transfer to the catalytic site. The results indicate that the Glu-15^II is the only essentially crucial residue of the K^B pathway, but that the Tyr-248 also plays a distinct role in defining an internal proton donor and controlling the dynamics of proton transfer to the pump site and the catalytic site.     

Astigmatism of a thick cylindrical object in reflective mode CSLM

The axial response of a basic confocal microscope is determined when the sample is a thick cylindrical or tubular structure. The response from the back wall of the cylindrical sample is split into two separate signals due to basic aberration or astigmatism effects.     

Computer-assisted manufacturing process optimization with neural networks

Today's manufacturing methods are caught between the growing need for quality, high process safety, minimal manufacturing costs, and short manufacturing times. In order to meet these demands, process setting parameters have to be chosen in the best possible way, according to demand on quality. For such optimization it is necessary to represent the processes in a model. Due to the enormous complexity of many processes and the high number of influencing parameters, however, conventional approaches to modelling and optimization are no longer sufficient. In this article it is shown how, by means of applying neural networks for process modelling, even these highly complex interdependencies can be learned. That way both process and quality parameters can be assessed before or during processing. By connecting them with corresponding cost models, it is possible to optimize processes with the help of evolutionary algorithms. Using examples of different manufacturing processes, the possi bilities for process modelling and optimization with neural networks and evolutionary algorithms are demonstrated.     

Invited paper Characteristics of travelling waves along the non-linear transmission lines for monolithic integrated circuits: a review

A general analysis of non-linear wave propagation along transmission lines with voltage-dependent capacitance is presented. In particular, slow-wave structures like MIS and Schottky-barrier strip lines are examined. A spatial periodicity is included explicitly. The theoretical treatment is based on suitable equivalent circuits leading to characteristic wave equations. With regard to practical devices, the solutions show a variety of different phenomena as determined by the parameters of the non-linearity, dispersion and dissipation and the boundary conditions. Experimental results performed on a slow-wave model line are included.     

A software tool for tomographic axial superresolution in STED microscopy

A method for generating three‐dimensional tomograms from multiple three‐dimensional axial projections in STimulated Emission Depletion (STED) superresolution microscopy is introduced. Our STED< method, based on the use of a micromirror placed on top of a standard microscopic sample, is used to record a three‐dimensional projection at an oblique angle in relation to the main optical axis. Combining the STED< projection with the regular STED image into a single view by tomographic reconstruction, is shown to result in a tomogram with three‐to‐four‐fold improved apparent axial resolution. Registration of the different projections is based on the use of a mutual‐information histogram similarity metric. Fusion of the projections into a single view is based on Richardson‐Lucy iterative deconvolution algorithm, modified to work with multiple projections. Our tomographic reconstruction method is demonstrated to work with real biological STED superresolution images, including a data set with a limited signal‐to‐noise ratio (SNR); the reconstruction software (SuperTomo) and its source code will be released under BSD open‐source license.     

Distributed mosfet amplifier using microstrip†

Viewing the input capacitance of a mosfet amplifier stage as an integral part of a microstrip transmission line, leads to a distributed amplifier of simple design. With today's mosfets, a bandwidth in excess of 500 MHz can be achieved ; it will be possible to extend this bandwidth substantially in the future by the use of mosfets with lower input capacitance. In addition, some data are given on transmission lines employing substrates of high dielectric permittivity.     

Self‐calibrated concentration measurements of polydisperse nanoparticles

Quantitative characterization of nanoparticles, e.g. accurate estimation of concentration distributions, is critical to many pharmaceutical and biological applications. We present a method that enables for the first time highly accurate size and absolute concentration measurements of polydisperse nanoparticles in solution, based on fluorescence single particle tracking, that are self‐calibrated in the sense that the detection region volume is estimated based on the tracking data. The method is evaluated using simulations and experimental data of polystyrene nanospheres in water/sucrose solution. In addition, the method is used to quantify aggregation and clearance of different types of liposomes after intravenous injection in rats, where additional and more accurate information can be obtained that was previously unavailable, which can help elucidate their usefulness as drug carriers.